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 to tissues. 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: ↑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, constipation, GI obstruction

GU: urinary hesitancy, urinary retention

Neuro: drowsiness, dizziness, excitation (in children)

Interactions ⬆ ⬇

Drug-drug:

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

Route/Dosage ⬆ ⬇

PO (Adults ): Immediate release:4 mg every 4–6 hr; Extended release: 8–12 mg of every 8–12 hr (not to exceed 24 mg/day).
PO (Children 6–12 yr): Immediate release: 2 mg 3–4 times daily (not to exceed 12 mg/day).

Availability ⬆ ⬇

(Generic available)

Immediate-release tablets: 4 mg^OTC
Extended-release tablets: 12 mg^OTC
Syrup: 2 mg/5 mL^OTC
In combination with:
decongestants^{Rx, OTC}. See Combination Drugs.

Assessment ⬆ ⬇

Assess allergy symptoms (rhinitis, sneezing, conjunctivitis, hives) before 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 ↓ 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 ↓ GI irritation. DNC: Swallow extended-release tablets whole; do not crush, break, or chew.
- Use calibrated measuring device to ensure accurate dose of liquid.

Patient/Family Teaching ⬆ ⬇

Explain the purpose and side effects of chlorpheniramine. Instruct patient to take as directed. Advise patient to read Patient Information before starting therapy.
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.
Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications.
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 yr.
Instruct patient to contact health care professional if symptoms persist.
Rep: Advise women of reproductive potential to notify health care professional if pregnancy is planned or suspected and to avoid breastfeeding during therapy.

section name header

Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇