Respiratory Care Pharmacology: Drug Classes and Clinical Uses

Respiratory care pharmacology focuses on the medications used to treat pulmonary disease, support ventilation, manage airway obstruction, control inflammation, improve secretion clearance, treat respiratory infections, and stabilize critically ill patients.

Respiratory therapists encounter drugs delivered by inhalation as well as medications administered orally, intravenously, intramuscularly, and through other routes. Understanding these therapies requires more than memorizing drug names.

Clinicians must know how medications work, how they are delivered, what adverse effects they can produce, and how to determine whether the patient is experiencing a meaningful therapeutic response.

 

What Is Respiratory Care Pharmacology?

Respiratory care pharmacology is the study and clinical application of medications that affect the respiratory system and the critically ill patients commonly managed by respiratory therapists.

The field includes medications used to:

• Relax bronchial smooth muscle
• Reduce airway inflammation
• Thin or modify respiratory secretions
• Treat bacterial, viral, and fungal infections
• Lower pulmonary vascular resistance
• Provide sedation and analgesia
• Produce neuromuscular blockade
• Support blood pressure and cardiac function
• Treat pulmonary edema
• Assist with emergency resuscitation
• Manage neonatal and pediatric respiratory disorders

Many respiratory drugs are delivered directly into the lungs as aerosols. Others are administered systemically because their therapeutic targets extend beyond the respiratory tract.

The respiratory therapist must understand the purpose of each medication, how it reaches its target, how quickly it acts, how long its effects last, and which complications may occur.

Basic Principles of Pharmacology

Drug therapy can be understood through three major phases: drug administration, pharmacokinetics, and pharmacodynamics.

Drug Administration

The drug administration phase describes how a medication is prepared and introduced into the body.

Common routes include:

• Inhalation
• Oral administration
• Intravenous administration
• Intramuscular injection
• Subcutaneous injection
• Endotracheal administration
• Topical administration
• Transdermal administration

The inhaled route is especially important in respiratory care because it allows medication to be delivered directly to the lungs. Compared with systemic therapy, inhaled medication may provide several advantages, including smaller required doses, rapid onset, direct targeting of the respiratory tract, and fewer systemic effects.

However, inhaled therapy does not guarantee that the entire dose reaches the lungs. Some medication may remain inside the device, deposit in the mouth or throat, or be swallowed. Correct device selection and proper administration technique are therefore essential.

Pharmacokinetics

Pharmacokinetics describes what the body does to a medication after it is administered.

The four major components are:

• Absorption
• Distribution
• Metabolism
• Elimination

Absorption refers to movement of the medication from its administration site into the bloodstream or target tissue. Distribution describes movement of the medication through the circulation and into tissues. Metabolism is the chemical alteration of the medication, primarily by the liver. Elimination refers to removal of the medication or its metabolites, often through the kidneys.

Several patient factors can alter pharmacokinetics. Liver disease may slow metabolism, while renal disease may reduce drug elimination. These changes can increase medication concentrations and the risk of toxicity.

Bioavailability and Half-Life

Bioavailability refers to the proportion of an administered medication that reaches the systemic circulation.

Intravenous medications have essentially complete systemic availability because they enter the bloodstream directly. Oral medications may lose some active drug through gastrointestinal absorption problems or first-pass metabolism in the liver.

The half-life of a medication is the time required for its plasma concentration to decrease by approximately 50%.

Half-life helps determine how often a drug must be administered. Shorter-acting medications generally require more frequent dosing, whereas medications with longer half-lives can often be given less frequently.

Pharmacodynamics

Pharmacodynamics describes what a medication does to the body. Many drugs exert their effects by binding to receptors. An agonist activates a receptor and produces a physiologic response. An antagonist binds to a receptor and blocks or reduces its activation.

The magnitude of the clinical response often depends on the drug concentration and the number of receptors affected. Other important concepts include receptor selectivity, drug potency, maximal effect, tolerance, and therapeutic index.

Note: A drug with a narrow therapeutic range requires careful monitoring because the concentration producing benefit may be relatively close to the concentration that produces toxicity.

Autonomic Control of the Airways

The autonomic nervous system plays a major role in determining airway smooth-muscle tone. The sympathetic and parasympathetic nervous systems influence the airways through different receptors and neurotransmitters.

Beta-Adrenergic Receptors

Stimulation of beta-2 adrenergic receptors relaxes bronchial smooth muscle. This produces bronchodilation, increases airway diameter, lowers airway resistance, and can improve expiratory airflow.

Beta-2 receptors are therefore the principal targets of many commonly used bronchodilator medications. Beta-1 receptors are found predominantly in the heart. Their stimulation increases heart rate and myocardial activity.

Because excessive beta-1 stimulation can produce unwanted cardiovascular effects, respiratory medications with greater beta-2 selectivity are generally preferred when bronchodilation is the primary goal.

Muscarinic Receptors

Parasympathetic nerves release acetylcholine, which binds to muscarinic receptors. Stimulation of M3 muscarinic receptors on airway smooth muscle produces bronchoconstriction. Acetylcholine also contributes to mucus gland secretion.

Anticholinergic medications block these receptors and reduce cholinergic bronchoconstriction. Understanding beta-adrenergic and muscarinic receptor activity provides the foundation for understanding the two major inhaled bronchodilator classes.

Aerosol Drug Delivery

Aerosol therapy is one of the most important components of respiratory care pharmacology. An aerosol consists of liquid or solid particles suspended in a gas.

For an inhaled drug to be effective, particles must leave the delivery device, enter the patient’s respiratory tract, avoid excessive deposition in the mouth and upper airway, and reach the intended region of the lungs.

Factors Affecting Aerosol Deposition

Several factors influence how much medication reaches the lower respiratory tract, including:

• Particle size
• Inspiratory flow
• Breathing pattern
• Airway anatomy
• Airway obstruction
• Device design
• Patient cooperation
• Humidification
• Artificial airways
• Ventilator circuit configuration

Note: Particle size is particularly important. Larger particles tend to deposit in the mouth, nose, and central airways. Smaller respirable particles are more likely to penetrate into the lower respiratory tract. The amount of medication prescribed is therefore not the same as the amount ultimately deposited in the lungs.

Aerosol Delivery Devices

Common aerosol-delivery systems include nebulizers, pressurized metered-dose inhalers, dry-powder inhalers, and soft-mist inhalers.

Small-Volume Nebulizers

Small-volume nebulizers convert liquid medication into an inhalable aerosol. Jet nebulizers use compressed gas to generate aerosol particles. Advantages include relatively little need for patient coordination and the ability to administer larger medication doses.

Nebulizers are especially useful for:

• Young children
• Patients in respiratory distress
• Patients unable to coordinate an inhaler
• Mechanically ventilated patients
• Patients receiving continuous bronchodilator therapy

Note: Potential disadvantages include longer treatment times, medication waste, contamination risk, equipment requirements, and the need for proper cleaning.

Vibrating-Mesh Nebulizers

Vibrating-mesh nebulizers force liquid through microscopic openings to generate fine aerosol particles. They often have low residual medication volume and can provide efficient aerosol delivery.

They are quiet and may be used in a variety of clinical settings, including mechanical ventilation. Proper cleaning is essential because blockage or contamination of the mesh can interfere with performance.

Metered-Dose Inhalers

A pressurized metered-dose inhaler delivers a specific amount of medication with each actuation. MDIs are compact, portable, and convenient, but they require proper technique.

Correct administration generally includes:

• Exhaling before inhalation
• Creating a good mouth seal
• Actuating the inhaler at the beginning of inspiration
• Inhaling slowly and deeply
• Holding the breath briefly after inhalation

Note: Poor hand-breath coordination can substantially reduce pulmonary drug deposition.

Spacers and Valved Holding Chambers

A spacer or valved holding chamber can improve medication delivery from an MDI. These devices reduce the need for precise actuation-inhalation coordination and may decrease deposition of medication in the mouth and pharynx.

They are particularly useful with inhaled corticosteroids because reduced oropharyngeal deposition may lower the risk of local adverse effects. Only one medication actuation should generally be placed into the chamber at a time.

Dry-Powder Inhalers

Dry-powder inhalers are typically breath actuated. They reduce the need for hand-breath coordination, but they require sufficient inspiratory flow to disperse the medication.

For this reason, DPIs may not be appropriate for patients who are severely ill, very young, or unable to generate adequate inspiratory flow. Patients should also avoid exhaling into the device because moisture can interfere with powder dispersion.

Adrenergic Bronchodilators

Adrenergic bronchodilators stimulate beta receptors, primarily beta-2 receptors in airway smooth muscle. Their main therapeutic effect is bronchodilation.

They are frequently used for reversible airflow obstruction associated with conditions such as:

• Asthma
• COPD
• Acute bronchospasm
• Chronic bronchitis
• Emphysema
• Bronchiectasis
• Cystic fibrosis

Short-Acting Beta Agonists

Short-acting beta agonists, or SABAs, are primarily used for rapid relief of acute bronchospasm.

Common examples include:

• Albuterol
• Levalbuterol

These medications are often referred to as rescue bronchodilators because they act relatively quickly. Albuterol may be delivered through an MDI, nebulizer, or other approved formulation.

In severe acute bronchospasm, repeated doses or continuous nebulization may be used according to the patient’s condition and treatment protocol. The therapist should assess whether the medication actually improves airflow.

Indicators of a favorable response may include:

• Decreased wheezing
• Reduced dyspnea
• Improved breath sounds
• Increased peak expiratory flow
• Increased FEV1
• Decreased airway resistance
• Improved patient comfort

Long-Acting Beta Agonists

Long-acting beta agonists, or LABAs, provide prolonged bronchodilation and are used primarily for maintenance therapy.

Examples include:

• Salmeterol
• Formoterol
• Arformoterol
• Indacaterol
• Olodaterol
• Vilanterol

Note: LABAs are widely used in COPD and may also be used in asthma as part of an appropriate controller regimen. In asthma, LABAs should not be viewed as substitutes for anti-inflammatory therapy because they improve bronchomotor tone without adequately addressing the underlying airway inflammation.

Adverse Effects of Beta Agonists

Beta agonists can produce systemic effects, particularly at higher doses.

Potential adverse effects include:

• Tremor
• Nervousness
• Palpitations
• Tachycardia
• Headache
• Dizziness
• Increased blood pressure
• Arrhythmias

Note: The patient should be monitored during treatment, particularly when receiving frequent or high-dose bronchodilator therapy. A worsening heart rate or cardiac rhythm may require treatment interruption and reassessment.

Racemic Epinephrine

Racemic epinephrine differs from selective beta-2 bronchodilators because its adrenergic actions include vasoconstriction. This makes it especially useful for upper-airway edema.

Clinical situations may include:

• Croup
• Postextubation stridor
• Upper-airway swelling
• Selected forms of airway obstruction

Note: By constricting blood vessels in swollen mucosa, racemic epinephrine can reduce edema and improve airway caliber. Patients require continued observation because the clinical effect may be temporary and airway swelling may recur.

Anticholinergic Bronchodilators

Anticholinergic bronchodilators block acetylcholine at muscarinic receptors. This reduces parasympathetic-mediated bronchoconstriction.

These medications are especially important in COPD, where cholinergic airway tone contributes significantly to obstruction.

Ipratropium Bromide

Ipratropium bromide is a short-acting anticholinergic bronchodilator. It is commonly administered through a nebulizer or inhaler. Ipratropium may be combined with albuterol because the two medications produce bronchodilation through different mechanisms.

This combination is commonly used in COPD and may also be beneficial during severe asthma exacerbations.

Long-Acting Antimuscarinic Agents

Long-acting antimuscarinic agents, often called LAMAs, provide prolonged bronchodilation.

Examples include:

• Tiotropium
• Aclidinium
• Glycopyrrolate
• Umeclidinium

Note: LAMAs are commonly used as maintenance therapy for COPD. Some may also be used as add-on therapy in selected patients with asthma. LABA and LAMA medications are frequently combined to produce prolonged bronchodilation through complementary mechanisms.

Adverse Effects of Anticholinergics

Possible adverse effects include:

• Dry mouth
• Urinary retention
• Increased heart rate
• Blurred vision
• Pupillary dilation
• Increased intraocular pressure
• Altered mental status

Note: Aerosol exposure to the eyes should be minimized, particularly in patients susceptible to glaucoma.

Methylxanthine Bronchodilators

Methylxanthines include theophylline and aminophylline. These medications can produce bronchodilation and may affect respiratory drive and diaphragmatic function.

Their clinical use has declined because newer inhaled bronchodilators are generally easier to administer and have more predictable safety profiles. Theophylline has a relatively narrow therapeutic range, meaning that toxic concentrations may not be far above therapeutic concentrations.

Potential toxicity includes:

• Nausea
• Vomiting
• Nervousness
• Tremor
• Tachycardia
• Arrhythmias
• Seizures

Note: Drug concentrations may be influenced by liver function, smoking status, interacting medications, and individual metabolic differences. Careful monitoring is therefore essential.

Inhaled Corticosteroids

Inhaled corticosteroids are among the most important controller medications used for asthma. Unlike bronchodilators, corticosteroids do not primarily relax airway smooth muscle. Instead, they reduce airway inflammation.

Examples include:

• Budesonide
• Beclomethasone
• Fluticasone
• Mometasone
• Ciclesonide

Note: Corticosteroids reduce inflammatory-cell activity, mediator production, airway edema, and airway hyperresponsiveness. Their effects develop over time, so they are not intended for immediate relief of acute bronchospasm.

Adverse Effects of Inhaled Corticosteroids

Local adverse effects include:

• Oropharyngeal candidiasis
• Dysphonia
• Hoarseness
• Throat irritation
• Cough

Note: Using a spacer or holding chamber with an MDI can reduce upper-airway deposition. Patients should rinse the mouth after inhaled corticosteroid use to reduce the risk of candidiasis and other local effects. Higher doses and prolonged exposure may increase the risk of systemic corticosteroid effects.

Systemic Corticosteroids

Systemic corticosteroids may be administered orally or intravenously when stronger anti-inflammatory therapy is required.

They may be used in conditions such as:

• Severe asthma exacerbation
• COPD exacerbation
• Status asthmaticus
• Selected inflammatory lung diseases
• Certain critical-care conditions

Note: Systemic corticosteroids do not provide immediate bronchodilation. Their therapeutic effect may require several hours. Potential systemic adverse effects become increasingly important with larger doses and longer treatment durations.

Nonsteroidal Antiasthma Medications

Nonsteroidal antiasthma medications help control asthma by targeting inflammatory pathways and bronchial hyperresponsiveness without using corticosteroids. These drugs are generally used as long-term controller therapies rather than for immediate relief of acute bronchospasm.

Leukotriene-Modifying Drugs

Leukotrienes contribute to:

• Bronchoconstriction
• Mucus production
• Airway edema
• Inflammation

Medications that block leukotriene activity may improve asthma control.

Examples include:

• Montelukast
• Zafirlukast
• Zileuton

Note: These medications are controller therapies rather than rescue treatments for severe acute bronchospasm.

Cromolyn

Cromolyn is associated with stabilization of mast cells and reduction of inflammatory mediator release. Its role is preventive rather than immediately bronchodilating. Other biologic and targeted therapies may also be used for certain forms of severe asthma.

Mucoactive Medications

Respiratory secretions can become thick, tenacious, or difficult to clear. Mucoactive therapy attempts to change secretion properties or improve clearance.

Medication therapy should usually be combined with adequate hydration, coughing, suctioning, airway-clearance therapy, or other secretion-removal techniques when necessary.

N-Acetylcysteine

N-acetylcysteine, or NAC, is a mucolytic medication. It reduces mucus viscosity by disrupting chemical bonds within respiratory secretions. Potential indications include thick, difficult-to-clear mucus.

A major adverse effect is bronchospasm, especially in patients with reactive airways. Patients should be observed for increased wheezing, dyspnea, or deterioration in airflow after treatment. NAC also has a characteristic sulfur-like odor that some patients find unpleasant.

Dornase Alfa

Dornase alfa is particularly important in cystic fibrosis. Purulent cystic fibrosis secretions contain large amounts of extracellular DNA from degenerating inflammatory cells.

Dornase alfa breaks down this DNA and reduces sputum viscosity. This can improve secretion clearance and help preserve pulmonary function.

Hypertonic Saline

Hypertonic saline may be used to improve airway hydration and mobilize secretions. It is commonly associated with secretion-management strategies in cystic fibrosis and other disorders involving difficult mucus clearance.

Because hypertonic saline can irritate the airways, susceptible patients may require bronchodilator therapy beforehand.

Aerosolized Anti-Infective Medications

Certain antimicrobial medications can be inhaled directly into the respiratory tract. This allows relatively high local drug concentrations to reach infected airways while potentially limiting systemic exposure.

Inhaled Tobramycin

Tobramycin is an aminoglycoside antibiotic used in selected patients with chronic airway infection, particularly cystic fibrosis associated with Pseudomonas aeruginosa. Patients should be monitored for cough, bronchospasm, changes in pulmonary function, and medication tolerance.

Because aminoglycosides can produce systemic toxicity, renal and auditory concerns may also be relevant depending on the patient’s total exposure.

Inhaled Aztreonam

Aztreonam is another inhaled antibacterial medication used in selected patients with chronic pulmonary infection. It is particularly associated with treatment of Pseudomonas infection in cystic fibrosis. Specific formulations may require specific aerosol-delivery devices.

Pentamidine

Aerosolized pentamidine has been used in relation to Pneumocystis infection. Because aerosolized medication can expose healthcare personnel, proper environmental precautions and equipment are important. Cough and bronchospasm may occur during treatment.

Ribavirin

Ribavirin is an antiviral medication that has been administered by aerosol in selected clinical situations. Its administration requires specialized equipment and attention to environmental exposure.

Zanamivir

Zanamivir is an inhaled antiviral medication used against influenza. It inhibits viral neuraminidase and interferes with viral spread. Because bronchospasm can occur, caution is warranted in patients with underlying airway disease.

Pulmonary Surfactant Therapy

Pulmonary surfactant lowers surface tension within the alveoli and helps prevent alveolar collapse. Premature infants may have inadequate surfactant production, contributing to neonatal respiratory distress syndrome. Exogenous surfactant can improve lung compliance, alveolar stability, and oxygenation.

Examples include:

• Beractant
• Calfactant
• Poractant alfa

Note: Surfactant is administered directly into the airway rather than through a typical inhaler. Rapid changes in lung compliance and oxygenation can occur after administration, so ventilator settings and oxygen requirements may need prompt adjustment.

Inhaled Nitric Oxide

Inhaled nitric oxide is a selective pulmonary vasodilator. It relaxes pulmonary vascular smooth muscle, reducing pulmonary vascular resistance and pulmonary artery pressure. Because it is inhaled into ventilated regions of the lungs and rapidly inactivated after entering the bloodstream, its effects can be concentrated in the pulmonary circulation.

Nitric oxide is commonly associated with neonatal hypoxic respiratory failure and selected pulmonary hypertension conditions.

Important monitoring considerations include:

• Oxygenation response
• Delivered nitric oxide concentration
• Nitrogen dioxide concentration
• Methemoglobin levels
• System function
• Hemodynamic status

Note: Nitrogen dioxide is a toxic byproduct, making proper equipment setup and monitoring essential. Abrupt discontinuation may produce rebound pulmonary hypertension or worsening oxygenation, so nitric oxide should generally be withdrawn carefully.

Other Inhaled Pulmonary Vasodilators

Other pulmonary vasodilators include:

• Iloprost
• Treprostinil
• Epoprostenol

These medications act through prostacyclin-related pathways. Potential effects include pulmonary vasodilation and reduced platelet aggregation.

Adverse effects may include:

• Headache
• Hypotension
• Cough
• Syncope
• Increased bleeding risk

Note: Patients require assessment of blood pressure, oxygenation, symptoms, and overall clinical response.

Heliox Therapy

Although heliox is not a conventional medication, it is an important respiratory therapeutic gas. Heliox is a mixture of helium and oxygen. Helium is less dense than nitrogen, so replacing nitrogen with helium can reduce turbulence and resistance to airflow.

Heliox may reduce work of breathing in disorders involving significant airflow obstruction.

Possible applications include:

• Croup
• Postextubation stridor
• Upper-airway obstruction
• Severe obstructive airway disease

The required oxygen concentration must still be maintained. For example, an 80% helium and 20% oxygen mixture may not provide enough oxygen for a hypoxemic patient, requiring a mixture with a greater oxygen concentration.

Special equipment and flow correction may be necessary because helium behaves differently from air and oxygen in certain flowmeters and ventilators.

Pharmacology During Mechanical Ventilation

Mechanically ventilated patients frequently receive respiratory and systemic medications.

These drugs may be used to:

• Reduce airway resistance
• Treat bronchospasm
• Control inflammation
• Provide analgesia
• Reduce anxiety
• Improve ventilator synchrony
• Facilitate intubation
• Produce paralysis
• Control pulmonary hypertension
• Treat seizures or neurologic problems

Note: Drug effects can significantly influence ventilatory requirements, respiratory drive, hemodynamics, and consciousness.

Aerosol Therapy During Mechanical Ventilation

Bronchodilators and other inhaled medications can be delivered through a ventilator circuit.

Medication delivery depends on several factors, including:

• Aerosol device placement
• Artificial airway diameter
• Circuit configuration
• Humidification
• Inspiratory flow
• Ventilator settings
• Patient effort

A particularly important consideration is the heat-and-moisture exchanger (HME). An HME can trap aerosol particles and substantially reduce medication delivery.

It should therefore be removed from the aerosol pathway when appropriate during medication administration. The aerosol generator must also be positioned correctly within the circuit to maximize pulmonary deposition.

Sedatives and Anxiolytics

Mechanically ventilated patients may experience anxiety, fear, sleep disruption, and discomfort. Sedative medications may improve comfort and patient-ventilator interaction.

Benzodiazepines

Benzodiazepines enhance inhibitory activity in the central nervous system.

Examples include:

• Midazolam
• Lorazepam
• Diazepam

Potential clinical effects include:

• Sedation
• Anxiety reduction
• Muscle relaxation
• Amnesia

Note: Excessive sedation can suppress respiratory drive, prolong mechanical ventilation, and contribute to hemodynamic depression. The depth of sedation should therefore be regularly reassessed.

Propofol

Propofol is commonly used for sedation in critically ill and mechanically ventilated patients. It has a relatively rapid onset and allows the depth of sedation to be adjusted quickly. Careful monitoring is necessary because it can produce cardiovascular and respiratory depression.

Dexmedetomidine

Dexmedetomidine may provide sedation while allowing some patients to remain more arousable than with deeper sedative regimens.

It can be useful for selected mechanically ventilated patients, but cardiovascular effects such as bradycardia and hypotension require monitoring.

Opioid Analgesics

Pain can increase heart rate, blood pressure, metabolic demand, anxiety, and ventilator dyssynchrony. Opioids are commonly used to provide analgesia in critically ill patients. Examples include morphine and fentanyl.

Potential adverse effects include:

• Respiratory depression
• Sedation
• Hypotension
• Bradycardia
• Nausea
• Constipation
• Delayed gastric emptying

High doses of fentanyl may occasionally produce chest-wall rigidity severe enough to interfere with ventilation. Naloxone (Narcan) is an opioid antagonist used to reverse opioid effects.

Reversal should be approached carefully because it may abruptly eliminate analgesia and cause severe pain or sympathetic stimulation.

Neuromuscular Blocking Agents

Neuromuscular blocking agents produce skeletal muscle paralysis.

They may be used during:

• Rapid sequence intubation
• Surgery
• Selected cases of severe ventilator dyssynchrony
• Situations requiring complete control of ventilation

Note: Two major categories include depolarizing and nondepolarizing agents.

Succinylcholine

Succinylcholine is a depolarizing neuromuscular blocker. It produces rapid paralysis and is commonly associated with intubation. Important complications include apnea and the rare development of malignant hyperthermia.

Nondepolarizing Agents

Examples include:

• Rocuronium
• Vecuronium
• Pancuronium
• Cisatracurium

Note: These medications interfere with acetylcholine at the neuromuscular junction and prevent skeletal-muscle contraction.

Paralysis Does Not Provide Sedation

A critical principle is that neuromuscular blocking agents do not provide:

• Pain relief
• Sedation
• Amnesia
• Anxiety control

Note: A paralyzed patient may remain fully conscious. Adequate sedation and analgesia must therefore be maintained whenever clinically appropriate. Because neuromuscular blockers paralyze respiratory muscles, mechanical ventilation and continuous monitoring are mandatory.

Diuretics in Respiratory Care

Diuretics are frequently encountered when pulmonary congestion or fluid overload contributes to respiratory distress. Furosemide is a commonly used loop diuretic.

Diuresis can reduce circulating volume and pulmonary hydrostatic pressure, helping improve pulmonary edema associated with heart failure.

Potential complications include:

• Hypovolemia
• Electrolyte disturbances
• Renal dysfunction
• Hypotension
• Acid-base abnormalities

Note: Respiratory therapists should understand how diuretic therapy may influence oxygenation, pulmonary edema, blood pressure, and laboratory values.

Vasopressors and Inotropes

Critically ill patients may require medications that support blood pressure and cardiac output. Vasopressors increase vascular tone. Inotropes increase myocardial contractility.

Common agents include:

• Norepinephrine
• Epinephrine
• Dopamine
• Phenylephrine
• Vasopressin
• Dobutamine

Adrenergic receptor activity helps explain many of their effects. Alpha-1 stimulation promotes vasoconstriction. Beta-1 stimulation increases cardiac contractility and heart rate. Beta-2 stimulation promotes smooth-muscle relaxation.

These drugs require close hemodynamic monitoring because excessive vasoconstriction, tachyarrhythmias, myocardial ischemia, and other complications can occur.

Anticoagulants, Antiplatelets, and Thrombolytics

Respiratory therapists frequently care for patients receiving medications that affect coagulation. These drugs are especially important in conditions such as pulmonary embolism, acute coronary syndromes, and stroke.

• Anticoagulants interfere with clotting pathways. Examples include heparin and related agents.
• Antiplatelet medications reduce platelet activation or aggregation.
• Thrombolytic medications actively promote breakdown of an existing thrombus.

Note: The major clinical concern with all of these therapies is bleeding. Patients should be monitored for evidence of hemorrhage and relevant laboratory changes.

Pediatric and Neonatal Pharmacology

Drug delivery to infants and children differs substantially from delivery to adults.

Factors include:

• Smaller airway diameter
• Lower tidal volume
• Different respiratory patterns
• Limited cooperation
• Mask fit
• Inspiratory-flow requirements
• Artificial-airway size

Young children may receive aerosol medications through nebulizers or MDIs with valved holding chambers and masks. A tight mask seal is important because leaks can dramatically reduce delivered medication.

Crying can also reduce lower-airway deposition. Intubated infants and children require careful aerosol-device placement because the endotracheal tube and ventilator circuit can substantially affect drug delivery.

Drug Dosage Calculations

Respiratory therapists must be comfortable with common medication calculations.

A useful relationship is:

Available dose / available volume = desired dose / required volume

Percentage-strength solutions must also be understood.

A 1% solution contains 1 gram of medication per 100 mL, which is equivalent to 10 mg/mL. A 0.5% solution contains 0.5 grams per 100 mL, or 5 mg/mL.

Careful attention to decimal placement and unit conversion is essential. Medication orders that appear unusually high, low, or otherwise questionable should be clarified before administration.

Assessing the Patient Before Medication Administration

Drug administration should begin with assessment. Before giving a respiratory medication, the clinician should determine:

• Why the medication is ordered
• The intended physiologic effect
• The correct dose and route
• Whether the patient has relevant allergies
• Whether contraindications are present
• Whether important drug interactions exist
• Whether the selected delivery device is appropriate
• Whether the patient can use the device correctly

Note: Baseline assessment may include respiratory rate, heart rate, breath sounds, work of breathing, oxygen saturation, secretion characteristics, blood pressure, pulmonary function data, and subjective symptoms.

Evaluating the Response to Therapy

Administration does not automatically mean therapy was successful. The patient’s response must be measured.

Bronchodilators

Indicators of improvement may include:

• Reduced wheezing
• Improved breath sounds
• Decreased dyspnea
• Increased peak expiratory flow
• Increased FEV1
• Lower airway resistance
• Reduced work of breathing

Mucoactive Therapy

Assessment may include:

• Secretion quantity
• Secretion viscosity
• Ability to expectorate
• Cough effectiveness
• Breath sounds
• Oxygenation

Anti-Inflammatory Therapy

Controller medications must usually be assessed over time.

Useful indicators include:

• Frequency of asthma symptoms
• Rescue inhaler use
• Nighttime awakenings
• Exacerbation frequency
• Activity tolerance
• Pulmonary function

Pulmonary Vasodilators

Assessment may include:

• Oxygenation
• Pulmonary artery pressure
• Pulmonary vascular resistance
• Blood pressure
• Clinical symptoms

Note: The respiratory therapist should also continuously monitor for adverse effects.

Medication Sequencing

When multiple aerosol medications are prescribed, the order of administration can influence treatment effectiveness. Bronchodilators are commonly given before medications that may benefit from improved airway caliber.

For example, bronchodilation may improve delivery of:

• Inhaled corticosteroids
• Mucolytics
• Hypertonic saline
• Inhaled antibiotics

Note: The exact sequence should still follow the prescribed treatment plan and the characteristics of the medications being used.

Patient Education and Adherence

Medication effectiveness depends heavily on whether the patient uses the medication correctly and consistently.

Patients should understand:

• The medication’s purpose
• Whether it is a rescue or maintenance drug
• How frequently it should be used
• Correct inhaler or nebulizer technique
• When to clean equipment
• Important adverse effects
• When to seek medical attention
• When the medication should not be overused

Patients often confuse controller medications with rescue medications. For example, an inhaled corticosteroid should not be expected to provide immediate relief from acute bronchospasm, while repeated reliance on a SABA may indicate inadequate disease control.

Note: Proper education can reduce these errors and improve long-term treatment effectiveness.

Respiratory Care Pharmacology Practice Questions

1. What is respiratory care pharmacology?
Respiratory care pharmacology is the study of medications used to treat respiratory diseases, improve airway function, control inflammation, manage secretions, support ventilation, and manage related critical care conditions.

2. What are the three major phases of drug action?
The three major phases of drug action are drug administration, pharmacokinetics, and pharmacodynamics.

3. What does pharmacokinetics describe?
Pharmacokinetics describes what the body does to a drug, including absorption, distribution, metabolism, and elimination.

4. What does pharmacodynamics describe?
Pharmacodynamics describes what a drug does to the body, including its interaction with receptors and the physiologic response that follows.

5. What is the difference between an agonist and an antagonist?
An agonist activates a receptor and produces a physiologic response, whereas an antagonist blocks a receptor and reduces or prevents its activation.

6. Why is inhalation an important route for respiratory medications?
Inhalation allows medication to be delivered directly to the respiratory tract, often producing a rapid effect with smaller doses and less systemic exposure than systemic administration.

7. Which adrenergic receptor is primarily responsible for bronchodilation?
The beta-2 adrenergic receptor is primarily responsible for bronchodilation because its stimulation relaxes bronchial smooth muscle.

8. What effect does stimulation of M3 muscarinic receptors have on the airways?
Stimulation of M3 muscarinic receptors promotes bronchoconstriction and contributes to mucus secretion.

9. What is the primary purpose of short-acting beta agonists?
Short-acting beta agonists are primarily used for rapid relief of acute reversible bronchospasm.

10. What are two common examples of short-acting beta agonists?
Albuterol and levalbuterol are two common short-acting beta agonists.

11. What is the main role of long-acting beta agonists?
Long-acting beta agonists provide prolonged bronchodilation for maintenance therapy rather than immediate rescue.

12. Name three examples of long-acting beta agonists.
Examples include salmeterol, formoterol, and arformoterol.

13. Why should long-acting beta agonists not be used alone for long-term asthma control?
Long-acting beta agonists do not adequately treat the underlying airway inflammation of asthma and should be used as part of an appropriate controller regimen that addresses inflammation.

14. What is racemic epinephrine commonly used to treat?
Racemic epinephrine is commonly used to reduce upper-airway swelling in conditions such as croup and postextubation stridor.

15. What adverse effects may occur with beta-adrenergic bronchodilators?
Potential adverse effects include tremor, nervousness, palpitations, tachycardia, headache, increased blood pressure, and arrhythmias.

16. How do anticholinergic bronchodilators produce bronchodilation?
Anticholinergic bronchodilators block acetylcholine at muscarinic receptors, reducing parasympathetic-mediated bronchoconstriction.

17. Which respiratory disease is especially associated with the use of anticholinergic bronchodilators?
Anticholinergic bronchodilators are especially important in the treatment of chronic obstructive pulmonary disease.

18. What is ipratropium bromide?
Ipratropium bromide is a short-acting anticholinergic bronchodilator commonly used alone or in combination with a beta agonist.

19. Why are albuterol and ipratropium often administered together?
They are often combined because they produce bronchodilation through different mechanisms, with albuterol stimulating beta-2 receptors and ipratropium blocking muscarinic receptors.

20. Name three long-acting antimuscarinic bronchodilators.
Examples include tiotropium, aclidinium, and umeclidinium.

21. What is the primary purpose of inhaled corticosteroids?
Inhaled corticosteroids are used to reduce airway inflammation and provide long-term control, particularly in asthma.

22. Why are inhaled corticosteroids not considered rescue medications?
They do not produce immediate bronchodilation and instead work over time to reduce airway inflammation and hyperresponsiveness.

23. What are common local adverse effects of inhaled corticosteroids?
Common local adverse effects include oropharyngeal candidiasis, dysphonia, hoarseness, throat irritation, and cough.

24. How can patients reduce oral and pharyngeal deposition of inhaled corticosteroids?
Using a spacer or valved holding chamber when appropriate and rinsing the mouth after administration can reduce oral and pharyngeal deposition.

25. What is N-acetylcysteine used for in respiratory care?
N-acetylcysteine is a mucolytic medication used to reduce the viscosity of thick respiratory secretions and make them easier to clear.

26. What is dornase alfa primarily used to treat?
Dornase alfa is primarily used in patients with cystic fibrosis to reduce the viscosity of thick respiratory secretions.

27. How does dornase alfa reduce mucus viscosity?
Dornase alfa breaks down extracellular DNA within purulent respiratory secretions, making the mucus less thick and easier to clear.

28. What respiratory complication can occur with N-acetylcysteine therapy?
N-acetylcysteine can provoke bronchospasm, especially in patients with reactive airways.

29. What role does hypertonic saline play in respiratory care?
Hypertonic saline helps hydrate airway secretions and improve mucus mobilization, particularly in patients with cystic fibrosis and other disorders involving difficult secretion clearance.

30. What is the main purpose of aerosolized anti-infective therapy?
Aerosolized anti-infective therapy delivers high concentrations of antimicrobial medication directly to the respiratory tract while potentially reducing systemic exposure.

31. What type of infection is inhaled tobramycin commonly used to manage?
Inhaled tobramycin is commonly used to manage chronic Pseudomonas aeruginosa infection in patients with cystic fibrosis.

32. What is inhaled aztreonam used for?
Inhaled aztreonam is used to treat chronic pulmonary infection caused by Pseudomonas aeruginosa, particularly in patients with cystic fibrosis.

33. What is aerosolized pentamidine associated with treating or preventing?
Aerosolized pentamidine is associated with the prevention or treatment of Pneumocystis infection.

34. What is ribavirin?
Ribavirin is an antiviral medication that may be administered by aerosol in selected respiratory viral infections.

35. What is zanamivir used to treat?
Zanamivir is an inhaled antiviral medication used to treat influenza by inhibiting viral neuraminidase.

36. Why should zanamivir be used cautiously in patients with underlying airway disease?
Zanamivir may provoke bronchospasm, so patients with asthma or other obstructive airway diseases require caution and monitoring.

37. What is the primary purpose of inhaled nitric oxide?
Inhaled nitric oxide is used as a selective pulmonary vasodilator to reduce pulmonary vascular resistance and improve pulmonary hemodynamics and oxygenation in selected patients.

38. Why is inhaled nitric oxide considered a selective pulmonary vasodilator?
It is delivered to ventilated regions of the lungs and is rapidly inactivated after entering the bloodstream, helping concentrate its vasodilating effect in the pulmonary circulation.

39. What important toxic byproduct must be monitored during inhaled nitric oxide therapy?
Nitrogen dioxide is an important toxic byproduct that must be monitored during inhaled nitric oxide administration.

40. Why should inhaled nitric oxide not be discontinued abruptly?
Abrupt discontinuation can cause rebound pulmonary hypertension and worsening oxygenation.

41. What is iloprost used for?
Iloprost is an inhaled prostacyclin analogue used to treat pulmonary hypertension by dilating pulmonary blood vessels.

42. What is treprostinil used for in respiratory care?
Treprostinil is an inhaled prostacyclin-related medication used to reduce pulmonary vascular resistance in patients with pulmonary hypertension.

43. What is the therapeutic purpose of heliox?
Heliox reduces gas density and turbulent airflow resistance, which can decrease the work of breathing in patients with significant airway obstruction.

44. What conditions may be treated with heliox?
Heliox may be used in conditions such as croup, postextubation stridor, upper-airway obstruction, and selected severe obstructive airway disorders.

45. Why may special correction factors be needed when using heliox with flowmeters or ventilators?
The lower density of helium can affect flow and volume measurements, so equipment may require specific correction factors or approved settings.

46. What should generally happen to a heat-and-moisture exchanger during aerosol administration through a mechanical ventilator?
The heat-and-moisture exchanger should generally be removed from the aerosol pathway because it can trap medication particles and greatly reduce drug delivery.

47. What factors can affect aerosol drug deposition during mechanical ventilation?
Factors include ventilator circuit configuration, humidification, artificial airway size, inspiratory flow, ventilator settings, patient effort, and aerosol-generator position.

48. What is the primary purpose of sedative medications in mechanically ventilated patients?
Sedatives are used to reduce anxiety and agitation, improve comfort, and help promote patient-ventilator synchrony.

49. What are three commonly used benzodiazepines in respiratory and critical care?
Midazolam, lorazepam, and diazepam are commonly used benzodiazepines.

50. Why must mechanically ventilated patients receiving sedatives be reassessed frequently?
Frequent reassessment is necessary because excessive sedation can suppress respiratory drive, cause hemodynamic depression, prolong mechanical ventilation, and delay recovery.

51. What is the primary purpose of opioid analgesics in mechanically ventilated patients?
Opioid analgesics are used to relieve pain, reduce the stress response, and improve comfort during mechanical ventilation and other critical care procedures.

52. What are common adverse effects of opioid medications?
Common adverse effects include respiratory depression, sedation, hypotension, bradycardia, nausea, constipation, delayed gastric emptying, and impaired ventilation.

53. What serious complication can occur with high-dose fentanyl administration?
High-dose fentanyl can cause chest-wall rigidity severe enough to interfere with ventilation.

54. What medication is used to reverse opioid effects?
Naloxone is an opioid antagonist used to reverse opioid-induced respiratory depression and other narcotic effects.

55. Why must naloxone be used carefully in a patient receiving opioids for severe pain?
Naloxone may rapidly reverse analgesia as well as respiratory depression, causing severe pain and sympathetic stimulation to return abruptly.

56. What are neuromuscular blocking agents used for in respiratory and critical care?
Neuromuscular blocking agents are used to produce skeletal muscle paralysis during procedures such as intubation and in selected patients requiring complete control of mechanical ventilation.

57. What is the major difference between depolarizing and nondepolarizing neuromuscular blockers?
Depolarizing agents initially activate and depolarize the neuromuscular end plate before causing paralysis, while nondepolarizing agents competitively block acetylcholine receptors at the neuromuscular junction.

58. What is succinylcholine?
Succinylcholine is a rapid-acting depolarizing neuromuscular blocking agent commonly used to facilitate endotracheal intubation.

59. Name three nondepolarizing neuromuscular blocking agents.
Examples include vecuronium, pancuronium, and cisatracurium.

60. What is the most important principle to remember about neuromuscular blockade?
Neuromuscular blocking agents provide paralysis only and do not provide sedation, analgesia, amnesia, or anxiety relief.

61. Why is mechanical ventilation mandatory during significant neuromuscular blockade?
Neuromuscular blockers paralyze the respiratory muscles, preventing the patient from maintaining adequate spontaneous ventilation.

62. What rare but potentially fatal complication is associated with succinylcholine?
Malignant hyperthermia is a rare but potentially fatal complication associated with succinylcholine.

63. How can acid-base status affect neuromuscular blockade?
Acidemia can intensify neuromuscular blockade, while alkalemia may reduce its effect.

64. What is propofol used for in respiratory and critical care?
Propofol is used for sedation, particularly when rapid onset and rapid adjustment of sedation depth are desirable.

65. What cardiovascular effects can occur with propofol?
Propofol can cause hypotension and cardiovascular depression, so close hemodynamic monitoring is required.

66. What is dexmedetomidine used for?
Dexmedetomidine is used for sedation and can help improve comfort and patient-ventilator interaction while allowing some patients to remain relatively arousable.

67. What are important adverse effects of dexmedetomidine?
Important adverse effects include bradycardia and hypotension.

68. Why are corticosteroids useful in severe asthma even though they are not bronchodilators?
Corticosteroids reduce airway inflammation, edema, and hyperresponsiveness, addressing the inflammatory component of severe asthma.

69. Why should corticosteroids not be relied upon as the only treatment for an acute asthma attack?
Their therapeutic effects are delayed and may require several hours, so rapid-acting bronchodilators are also needed for immediate bronchospasm relief.

70. What is theophylline?
Theophylline is a xanthine bronchodilator that can relax airway smooth muscle and may also influence ventilatory drive and diaphragmatic function.

71. Why does theophylline require careful monitoring?
Theophylline has a relatively narrow therapeutic range, and toxic concentrations can cause serious adverse effects such as arrhythmias and seizures.

72. What factors can alter theophylline blood concentrations?
Factors include smoking, liver function, interacting medications, and individual differences in drug metabolism.

73. What is the primary role of pulmonary surfactant?
Pulmonary surfactant reduces alveolar surface tension, helping maintain alveolar stability and prevent collapse.

74. In which condition is exogenous surfactant therapy especially important?
Exogenous surfactant therapy is especially important in premature infants with neonatal respiratory distress syndrome caused by surfactant deficiency.

75. Why must ventilator settings be reassessed after surfactant administration?
Surfactant can rapidly improve lung compliance and oxygenation, potentially changing the pressures and oxygen concentrations needed to ventilate the infant safely.

76. What is bioavailability?
Bioavailability is the proportion of an administered drug that reaches the systemic circulation and becomes available to produce an effect.

77. What is the first-pass effect?
The first-pass effect is the metabolism of an orally administered drug in the liver before a significant amount reaches the systemic circulation.

78. What is a drug’s half-life?
A drug’s half-life is the time required for its plasma concentration to decrease by approximately 50%.

79. Why is the therapeutic index important?
The therapeutic index reflects the margin between effective and toxic drug concentrations, so drugs with a narrow therapeutic index require especially careful monitoring.

80. What is the purpose of a spacer or valved holding chamber with a metered-dose inhaler?
A spacer or valved holding chamber reduces the need for precise hand-breath coordination and can decrease medication deposition in the mouth and pharynx.

81. How should a patient generally inhale when using a metered-dose inhaler?
The patient should begin a slow, deep inspiration as the medication is actuated and then hold the breath briefly to promote pulmonary deposition.

82. Why are dry-powder inhalers not appropriate for every patient?
Dry-powder inhalers require adequate inspiratory flow to disperse the medication, so patients who are very young, severely ill, or unable to inhale forcefully may not use them effectively.

83. Why should a patient avoid exhaling into a dry-powder inhaler?
Exhaling into a dry-powder inhaler can introduce moisture into the device and interfere with proper powder dispersion.

84. What is an important advantage of a vibrating-mesh nebulizer?
A vibrating-mesh nebulizer can provide efficient aerosol delivery with low residual medication volume and relatively little drug waste.

85. What is one disadvantage of a jet nebulizer?
Jet nebulizers may require longer treatment times and can leave residual medication in the device, resulting in medication waste.

86. Why is device selection important in aerosol therapy?
Device selection is important because medication delivery depends on the patient’s age, coordination, inspiratory ability, clinical condition, and ability to use the device correctly.

87. What is the purpose of bronchodilator assessment before and after treatment?
Bronchodilator assessment determines whether airway obstruction is present and whether the medication produces measurable improvement in airflow or symptoms.

88. Which pulmonary function measurements can help evaluate bronchodilator response?
Peak expiratory flow and FEV1 can help determine whether bronchodilator therapy has improved expiratory airflow.

89. Why is patient-reported breathing effort important when evaluating respiratory medications?
Subjective improvement in dyspnea or breathing effort can provide useful evidence of therapeutic benefit when considered along with objective findings.

90. What should be assessed before administering a mucoactive medication?
The clinician should assess secretion amount, color, consistency, cough effectiveness, breath sounds, oxygenation, and the patient’s ability to clear mucus.

91. Why does thinning mucus not always result in successful secretion clearance?
Thinner secretions still require an effective cough, suctioning, or another airway-clearance technique to be removed from the respiratory tract.

92. Why are bronchodilators sometimes administered before secretion therapies?
Opening the airways first may reduce bronchospasm and improve the delivery and tolerance of subsequently administered secretion-management medications.

93. Why are some inhaled anti-infective medications restricted to specific nebulizer systems?
Certain drug formulations have been tested and designed for particular devices, so using the correct nebulizer helps ensure appropriate aerosol characteristics and drug delivery.

94. What should be monitored during aerosolized anti-infective therapy?
The clinician should monitor respiratory symptoms, pulmonary function, cough, bronchospasm, sputum characteristics, medication tolerance, and the overall response to infection treatment.

95. Why are respiratory personnel precautions important when administering certain aerosolized anti-infective drugs?
Some aerosolized medications can escape into the environment and expose healthcare workers, so proper equipment and environmental controls may be required.

96. What is the purpose of diuretics in a patient with cardiogenic pulmonary edema?
Diuretics help remove excess sodium and water, reducing circulating volume and pulmonary vascular pressure that contribute to pulmonary congestion.

97. What are important complications of excessive diuretic therapy?
Excessive diuresis can cause hypovolemia, hypotension, electrolyte disturbances, renal dysfunction, and acid-base abnormalities.

98. What is the primary difference between a vasopressor and an inotrope?
A vasopressor primarily increases vascular tone and blood pressure, while an inotrope primarily increases the force of myocardial contraction.

99. Why can nonselective beta blockers be concerning in patients with reactive airway disease?
Nonselective beta blockers can inhibit beta-2 receptors in the airways, potentially opposing bronchodilation and worsening bronchospasm in susceptible patients.

100. What is the overall clinical approach to safe respiratory medication therapy?
Safe respiratory medication therapy requires assessing the patient, selecting and delivering the correct drug and dose, monitoring for therapeutic and adverse effects, documenting the response, and reassessing whether therapy should continue or be modified.

Final Thoughts

Respiratory care pharmacology extends from basic aerosolized bronchodilators to complex medications used during mechanical ventilation, pulmonary hypertension, infection, neonatal care, and cardiovascular emergencies.

Effective treatment depends on understanding the drug’s mechanism, indication, route, delivery device, expected response, and potential complications. Respiratory therapists must connect pharmacology with pulmonary physiology and patient assessment rather than relying on memorization alone.

Whether administering albuterol, corticosteroids, inhaled antibiotics, nitric oxide, sedatives, or neuromuscular blockers, the same principle applies: assess the patient, deliver the medication correctly, monitor the response, recognize adverse effects, and determine whether continued therapy remains appropriate.