Module 2: Drugs Acting on the Respiratory System

Vocabulary flashcards covering respiratory anatomy, antihistamines, antitussives, methylxanthines, mucolytics, and expectorants based on NCM106PHR Pharmacology lecture notes.

Respiratory System Anatomy

The anatomical structure divided into the upper respiratory system (nasal cavity, nostril, oral cavity, pharynx, larynx) and lower respiratory system (trachea, main bronchi, lungs, diaphragm).

Antihistamines

Histamine 1 ($\text{H}_1$) receptor antagonists that block histamine at receptor sites to decrease nasopharyngeal secretions; used for colds and allergic rhinitis, but not effective in emergency situations like anaphylaxis.

Antihistamine Mechanism of Action

Competitive binding where antihistamines occupy $\text{H}_1$ receptors on blood vessels and nerves to block histamine released from mast cells.

1st Generation Antihistamines

Antihistamines such as diphenhydramine (Benadryl) that cause drowsiness, dry mouth, and other cholinergic symptoms.

2nd Generation Antihistamines

Non-sedating antihistamines (such as cetirizine, fexofenadine, loratadine, and azelastine) that have little to no effect on sedation and produce fewer anticholinergic symptoms.

Diphenhydramine (Benadryl)

A 1st generation antihistamine that blocks $\text{H}_1$ receptors, is $98\%$ protein bound, has an average half-life of $2\text{--}7\,\text{hours}$, and is contraindicated in narrow-angle glaucoma due to anticholinergic effects.

Antitussives

Medications used to suppress or inhibit coughing by acting on the cough control center in the medulla; indicated for dry, nonproductive, and irritating coughs.

Dextromethorphan

A nonnarcotic antitussive that suppresses the medullary cough center without depressing respiration, causing no physical dependence or tolerance, with an onset of $15\text{--}30\,\text{minutes}$ and duration of $3\text{--}6\,\text{hours}$.

Benzonatate

An antitussive that acts by anesthetizing stretch receptors throughout the bronchi, alveoli, and pleura to relieve cough associated with pneumonia, bronchitis, the common cold, COPD, or during bronchoscopy.

Narcotic Antitussives

Opioid-derived antitussives (codeine and hydrocodone bitartrate) used to treat intractable cough usually associated with lung cancer.

Methylxanthines

Xanthine derivative bronchodilators (including theophylline, aminophylline, theophylline sodium glycinate, and oxtriphylline) that stimulate the CNS and respiration, dilate coronary and pulmonary vessels, and induce diuresis.

Theophylline

A methylxanthine bronchodilator that relaxes bronchial smooth muscle by inhibiting phosphodiesterase and increasing $\text{cAMP}$; maintained within a therapeutic range of $10\text{--}20\,\text{mcg/ml}$.

Pirbuterol

An aerosolized bronchodilator that acts as a $\beta_2$-adrenergic receptor agonist to relax bronchial smooth muscle, used alone or in combination with theophylline or steroid therapy.

Cromolyn Sodium

An inhaled prophylactic medication that stabilizes mast cell membranes to prevent the release of histamine and slow-reacting substances of anaphylaxis; not useful for acute asthma attacks.

Mucolytics

Agents that act directly on mucus to alter its molecular composition, liquefying and loosening sticky, thick respiratory secretions for easier elimination.

Acetylcysteine (Mucomyst)

A mucolytic administered via nebulization or orally that thins airway mucus and serves as an antidote when administered within $12\text{--}24\,\text{hours}$ of acetaminophen overdose.

Metered Dose Inhaler (MDI) Components

A portable inhalation device consisting of three main parts: the canister, plastic holder, and cap.

Nebulizer System Components

A device used to aerosolize liquid medications, consisting of an air compressor, air filter, tubing, nebulizer cup, and mouthpiece.

Dornase Alfa

An enzyme mucolytic that digests DNA in thick sputum secretions of patients with cystic fibrosis (CF), improving pulmonary function within $3\text{--}7\,\text{days}$.

Expectorants

Medications (such as guaifenesin) that increase respiratory tract fluid production to reduce mucus viscosity, adhesiveness, and surface tension, soothing respiratory membranes and promoting cough clearance.

Hydration in Respiratory Care

Considered the best natural expectorant for loosening and thinning bronchial secretions.