Respiratory Pharmacology

Question 1

Antihistamines (1st generation) (diphenhydramine, dimenhydrinate, chlorpheniramine)

Answer 1

MOA: Reversibly inhibit H1 histamine receptors.

Use: Allergy, motion sickness, sleep aid.

Adverse Effects: Sedation, antimuscarinic, anti-α-adrenergic

Question 2

Antihistamines (2nd generation) (loratadine, desloratdine, fexofenadine, cetirizine)

Answer 2

MOA: Reversibly inhibit H1 histamine receptors

Use: Allergy

Adverse Effects: Far less sedating than 1st generation because of ↓ entry into CNS

Question 3

Guaifenesin

Answer 3

MOA: Expectorant - thins secretions; does not suppress cough reflex.

Question 4

N-acetylcysteine

Answer 4

MOA: Mucolytic - liquefies mucus in COPD patients by disrupting disulfide bonds. Also used as an antidote for acetaminophen overdose.

Question 5

Dextromethorphan

Answer 5

MOA: Antitussive (antagonizes NMDA glutamate receptors). Synthetic codeine analog. Has mild opioid effect when used in excess

Adverse Effects: Mild abuse potential. Serotonin syndrome if combined with other serotonergic agents.

Toxicity Tx: Naloxone

Question 6

Pseudephedrine, phenylephrine

Answer 6

MOA: α-adrenergic agonists, used as nasal decongestants.

Use: Reduce hyperemia, edema, nasal congestion; open obstructed eustachian tubes. Pseudephedrin also illicitly used to make methamphetamine.

Adverse Effects: Hypertension. Can also cause CNS stimulation/anxiety (pseudoephedrine).

Question 7

Bosentan

Answer 7

MOA: Competitively antagonizes endothelin-1 receptors → ↓ pulmonary vascular resistance

Use: Pulmonary HTN

Adverse Effects: Hepatotoxic (monitor LFTs)

Question 8

Sildenafil

Answer 8

MOA: Inhibits cGMP PDE-5 and prolongs vasodilatory effect of nitric oxide.

Use: Pulmonary HTN

Question 9

Epoprostenol, iloprost

Answer 9

MOA: PGI2 (prostacyclin) with direct vasodilatory effects on pulmonary and systemic arterial vascular beds. Inhibits platelet aggregation.

Use: Pulmonary HTN

Side Effects: flushing, jaw pain

Question 10

Albuterol

Answer 10

MOA: Relaxes bronchial smooth muscle (short acting β2-agonist)

Use: Acute exacerbation of asthma

Question 11

Salmeterol, formoterol

Answer 11

MOA: Long acting β2-agonist

Use: Prophylaxis of asthma attacks

Adverse Effects: Tremor, arrhythmia, hpokalemia

Question 12

Fluticasone, budesonide

Answer 12

MOA: Inhaled cortiocsteroid, inhibit synthesis of virtually all cytokines. Inactivate NF-κB, the transcription factor that induces production of TNF-α and other inflammatory agents.

Use: 1st line for chronic asthma

Question 13

Ipratropium

Answer 13

MOA: Competitively blocks muscarinic receptors, preventing bronchoconstriction.

Use: Asthma, COPD.

Question 14

Montelukast, zafirlukast

Answer 14

MOA: Block leukotriene receptors (CysLT1)

Use: Aspirin-induced asthma

Question 15

Zileuton

Answer 15

MOA: 5-lipoxygenase pathway inhibitor. Blocks conversion of arachidonic acid to leukotrienes.

Use: 1st line for acute asthma exacerbations

Adverse Effects: Hepatotoxic

Question 16

Omalizumab

Answer 16

MOA: Binds mostly unbound serum IgE and blocks binding to FcεRI.

Use: Allergic asthma with ↑ IgE levels resistant to inhaled steroids and long-acting β2-agonists

Question 17

Theophylline

Answer 17

MOA: Likely causes bronchodilation by inhibiting PDE → ↑ cAMP levels due to ↓ cAMP hydrolysis

Adverse Effects: Usage limited because of narrow therapeutic index (cardiotoxicity, neurotoxicity)

Question 18

Methacholine

Answer 18

MOA: Muscarinic receptor (M3 antagonist)

Use: Bronchial challenge test to help diagnose asthma