4.1 Respiratory Pharmacology

Why Pharmacology Anchors the Interventions Domain

The Therapist Multiple-Choice (TMC) exam is the 160-question, 3-hour National Board for Respiratory Care (NBRC) test that earns the Certified Respiratory Therapist (CRT) credential and, at the higher cut score, qualifies you for the Clinical Simulation Examination on the path to Registered Respiratory Therapist (RRT). Pharmacology items are concentrated in the Initiation and Modification of Interventions section, the largest scored area.

You must match each drug to its class, mechanism, indication, route/dose, and characteristic adverse effect — the exam rarely asks pure recall; it embeds the drug in a scenario and asks what to give, withhold, or recognize.

Bronchodilators

Short-Acting Beta-2 Agonists (SABAs) — Rescue Medications:

SABAs bind beta-2 receptors on bronchial smooth muscle, activating adenylate cyclase and raising cyclic AMP to relax the airway. Albuterol is the first-line agent for acute bronchospasm; in status asthmaticus it can be given as continuous nebulization (10-15 mg/h). Levalbuterol is the purified R-isomer marketed to reduce tachycardia, though the evidence is modest. Side effects flow directly from receptor pharmacology: tachycardia (beta-1 spillover), fine skeletal tremor and hypokalemia (beta-2 drives potassium intracellularly), nervousness, and palpitations.

Long-Acting Beta-2 Agonists (LABAs) — Maintenance Only: salmeterol (onset 30-60 min, 12 h), formoterol (onset 5-15 min, 12 h), olodaterol (24 h). A common trap: formoterol has a fast onset yet is still a maintenance drug — never use any LABA as a rescue inhaler. LABA monotherapy in asthma carries an FDA black box warning for increased severe exacerbations and asthma deaths, so a LABA is always paired with an ICS (e.g., fluticasone/salmeterol = Advair). LABA monotherapy is acceptable in COPD.

Anticholinergics (Muscarinic Antagonists): ipratropium (Atrovent, SAMA, 0.5 mg SVN, 4-6 h) and tiotropium (Spiriva, LAMA, 18 mcg DPI daily, 24 h) block M3 receptors, cutting bronchoconstriction and secretions. Watch for dry mouth, urinary retention, and blurred vision/pupil dilation if sprayed in the eyes. Avoid the nebulized form in narrow-angle glaucoma, and screen for soy/peanut allergy (older ipratropium formulations). Albuterol + ipratropium (DuoNeb) is the additive standard for an acute COPD exacerbation.

Anti-Inflammatory, Mucoactive, and Critical-Care Agents

Inhaled and Systemic Corticosteroids

Inhaled corticosteroids (ICS) — fluticasone (Flovent), budesonide (Pulmicort), beclomethasone (QVAR), mometasone (Asmanex) — suppress airway inflammation, edema, and mucus, but effects build over days to weeks, so they are never the answer for acute bronchospasm. The signature local side effects are oral candidiasis (thrush) and dysphonia/hoarseness; teach patients to rinse and spit after each use and to attach a valved holding chamber (spacer) to an MDI to cut oropharyngeal deposition.

For an active exacerbation, reach for systemic steroids: IV methylprednisolone (Solu-Medrol) for severe presentations, oral prednisone tapers for moderate flares, and dexamethasone for pediatric croup and for hospitalized hypoxemic COVID-19. Long-term systemic steroids cause hyperglycemia, osteoporosis, immunosuppression, weight gain, and adrenal suppression — never stop them abruptly.

Mucolytics and Airway Clearance Pharmacology

A classic distractor pits NAC against dornase alfa: NAC is broad-use (and can trigger bronchospasm, so pretreat with albuterol), whereas dornase alfa is CF-specific and targets DNA, not disulfide bonds. Hypertonic saline can also provoke cough and bronchospasm during sputum induction.

Surfactant and ICU Medications

Exogenous surfactant — beractant (Survanta), poractant (Curosurf), calfactant (Infasurf) — is instilled through the endotracheal tube for neonatal RDS from surfactant deficiency; it has not shown consistent benefit in adult ARDS. For the ventilated adult, know these four classes:

• Analgesics first (fentanyl, morphine, hydromorphone): treat pain before sedating — an "analgosedation" approach.
• Sedatives (propofol — watch propofol-related infusion syndrome and triglycerides; midazolam; dexmedetomidine, which sedates without respiratory depression).
• Neuromuscular blockers / NMBAs (cisatracurium, rocuronium, vecuronium): used in refractory ARDS and to facilitate prone positioning. They paralyze the diaphragm but do not cross the blood-brain barrier, so they provide no sedation or analgesia — concurrent deep sedation is mandatory, a heavily tested patient-safety point.
• Vasopressors (norepinephrine first-line for septic shock, vasopressin, epinephrine) for hemodynamic instability.

Aerosolized Antimicrobials and Pulmonary Vasodilators

Two more device-delivered drug groups appear in scenarios. Inhaled antimicrobials include tobramycin (TOBI) and aztreonam (Cayston) for chronic Pseudomonas in cystic fibrosis, inhaled pentamidine for Pneumocystis prophylaxis (which requires a one-way valved nebulizer and negative-pressure room to protect staff), and ribavirin (Virazole) for severe RSV via a small-particle aerosol generator — pregnant staff should avoid the latter two.

Inhaled pulmonary vasodilators such as nitric oxide (iNO) and inhaled epoprostenol (Flolan) selectively dilate vessels in ventilated lung units to improve oxygenation in persistent pulmonary hypertension of the newborn and refractory ARDS; abrupt iNO withdrawal causes rebound pulmonary hypertension, so wean it gradually.

Exam trap to memorize: if a stem describes a wheezing patient with an SpO2 of 88% who needs immediate relief, the answer is albuterol — not a LABA, ICS, or steroid, no matter how attractive those distractors look.