chlorpheniramine

Antagonizes the effects of histamine at H₁-receptor sites; does not bind to or inactivate histamine.

Therapeutic effects:

Decreased symptoms of histamine excess (sneezing, rhinorrhea, nasal and ocular pruritus, ocular tearing, and redness).

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration.

Distribution: Widely distributed. Minimal amounts excreted in breast milk. Crosses the blood-brain barrier.

Metabolism/Excretion: Extensively metabolized by the liver.

Half-Life: 12–15 hr.

Time/Action Profile ⬆ ⬇

(antihistaminic effects)

ROUTE	ONSET	PEAK	DURATION
PO	15–30 min	6 hr	4–12 hr
PO–ER	unknown	unknown	8–24 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Acute attacks of asthma;
Known alcohol intolerance (some liquid forms);
Lactation: Lactation;
Pedi: Children 4 yr (OTC cough and cold products containing this medication should be avoided).

Use Cautiously in:

Angle-closure glaucoma;
Liver disease;
OB: Safety not established in pregnancy;
Geri: Appears on Beers list. risk of anticholinergic adverse reactions in older adults, including falls, delirium, and dementia. Avoid use in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

CV: hypertension, arrhythmias, hypotension, palpitations

EENT: blurred vision

GI: dry mouth, GI obstruction, constipation

GU: retention, urinary hesitancy

Neuro: drowsiness, dizziness, excitation (in children)

Interactions ⬆ ⬇

Drug-drug:

↑CNS depression with other CNS depressants, including alcohol, opioid analgesics, and sedative/hypnotics.
MAO inhibitors intensify and prolong anticholinergic effects of antihistamines.
↑anticholinergic effects with other drugs possessing anticholinergic properties, including antidepressants, atropine, haloperidol, phenothiazines, quinidine, and disopyramide.

Route/Dosage ⬆ ⬇

PO (Adults ): 4 mg every 4–6 hr or 8–12 mg of extended-release formulation every 8–12 hr (not to exceed 24 mg/day).
PO Geriatric Patients ): 4 mg twice daily or 8 mg of extended-release formulation at bedtime.
PO (Children 6–12 yr): 2 mg 3–4 times daily (not to exceed 12 mg/day).

Availability ⬆ ⬇

(Generic available)

Tablets: 4 mg^{Rx, OTC}
Extended-release tablets: 12 mg^{Rx, OTC}
Syrup: 2 mg/5 mL^{Rx, OTC}
In combination with: hydrocodone; decongestantsRx, OTC. See Appendix [not included in this PDA edition].

Assessment ⬆ ⬇

Assess allergy symptoms (rhinitis, conjunctivitis, hives) prior to and periodically during therapy.
Geri: Assess for adverse anticholinergic effects (delirium, acute confusion, dizziness, dry mouth, blurred vision, urinary retention, constipation, tachycardia, dementia, falls) during therapy.
Assess lung sounds and character of bronchial secretions. Maintain fluid intake of 1500–2000 mL/day to decrease viscosity of secretions.

Lab Test Considerations:

May cause false-negative reactions on allergy skin tests; discontinue 4 days prior to testing.

Implementation ⬆ ⬇

PO: Administer with food or milk to decrease GI irritation. DNC: Swallow extended-release tablets whole; do not crush, break, or chew.
- Administer syrup with an accurate measuring device; do not use a household teaspoon (overdose may occur).

Patient/Family Teaching ⬆ ⬇

Instruct patient to take chlorpheniramine as directed.
May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to drug is known.
Caution patient to avoid using alcohol or other CNS depressants concurrently with this drug.
Advise patient that good oral hygiene, frequent rinsing of mouth with water, and sugarless gum or candy may help relieve dryness of mouth.
Caution parents to avoid giving OTC cough and cold products to children <4 yrs.
Instruct patient to contact health care professional if symptoms persist.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected and to avoid breastfeeding during therapy. Monitor infants exposed to chlorpheniramine through breast milk for irritability and drowsiness.Caution parents to avoid OTC cough and cold products while breastfeeding.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇