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Chapter 7: Respiratory Drugs

TERMS TO LEARN

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Antitussive Drug that relieves or prevents cough.
Antihistamine Drug that counteracts histamine; can be divided into two groups: those that block H1 histamine receptors and those that block H2 receptors.
Area Postrema A region of the brain located in the medulla at the base of the 4th ventricle; location of the chemoreceptive trigger zone where vomiting is triggered.
Churg-Strauss Syndrome Vasculitis of the small arteries and veins; characterized by extravascular necrotizing granulomas; typically seen in patients with asthma or an allergy history.
Decongestant Drug that reduces congestion or swelling.
Expectorant Drug that promotes ejection of mucus or exudate from respiratory tract.

I. COLD MEDICATIONS

CLASSIFICATION OF COLD MEDICATIONS

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COLD MEDICATIONS: DRUG FACTS

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Drug Class Pharmacokinetics Mechanism of Action Drawbacks/Side Effects
Systemic Decongestants
Pseudoephedrine (Sudafed as well as numerous other OTC preparations)

  • α adrenergic agonist

  • A: PO

  • E: Primarily excreted unchanged in urine

  • α adrenergic stimulation in respiratory mucosa leads to vasoconstriction in the nasal mucosa causing decreased nasal congestion

  • Hypertension

  • Palpitations

  • Restricted access secondary to use in the illicit manufacturing of amphetamines
Phenylephrine (Sudafed PE as well as numerous OTC preparations)

  • A: PO, topical, nasal

  • M: Intestinal wall and hepatic

  • E: Metabolites excreted in urine

  • Hypertension

  • Reflex bradycardia

  • Decreased cardiac output
Diphenhydramine (Benadryl as well as numerous OTC preparations)

  • Antihistamine

  • A: PO, IM, IV, topical

  • M: Hepatic (P450)

  • E: Parent drug and metabolites excreted in urine

  • Blockade of histamine action of H1 receptors prevents stimulation of the sneeze reflex receptors

  • Sedation

  • Urinary retention

  • Inhibits P450 enzymes
Chlorpheniramine (Chlor-Trimeton as well as numerous OTC preparations)

  • A: PO

  • M: Hepatic (P450)

  • E: Metabolites excreted in urine
Topical Decongestants
Oxymetazoline (Afrin as well as numerous other OTC preparations)

  • α adrenergic agonist

  • A: Nasal

  • E: Primarily excreted unchanged in urine

  • α adrenergic stimulation in respiratory mucosa leads to vasoconstriction in the nasal mucosa causing decreased nasal congestion

  • Use with caution in patients with cardiac disease, hyperthyroidism, glaucoma, and diabetes

  • Rebound nasal congestion following cessation of chronic use
Phenylephrine (Neo-Synephrine)

  • A: PO, topical, nasal

  • M: Intestinal wall and hepatic

  • E: Metabolites excreted in urine
Naphazoline (Privine)

  • A: Nasal

  • M: Unavailable

  • E: Unavailable
Expectorant
Guaifenesin (Mucinex, Robitussin)

  • Expectorant

  • A: PO

  • M: Hepatic

  • E: Parent drug and metabolites excreted in urine

  • Thought to act as GI irritant triggering increased respiratory secretions therefore creating thinner, more voluminous mucus

  • Drowsiness

  • Renal stone formation with consumption of large quantities
Antitussive
Codeine

  • Centrally acting antitussive

  • Opioid

  • A: PO

  • M: Hepatic (P450)

  • E: Primarily excreted as metabolites in urine

  • Suppression of cough by action of the μ receptors in the area postrema

  • Nausea/vomiting

  • Constipation

  • Respiratory depression and death in pediatric patients in the setting of T&A

  • Histamine release associated ...

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