Drug reference

Chlorpheniramine

Antihistamine · Antiallergic, H1-receptor antagonist

Also known as Chlorphenamine, Chlorpheniramine Maleate

START

4 mg PO every 4-6 hours PRN (adults); 2 mg every 4-6 hours (geriatric)

TYPICAL MAX

24 mg/day (adults); 12 mg/day (geriatric and children 6-11 yrs); 6 mg/day (children 2-5 yrs)

STOP IF

Severe hypersensitivity (anaphylaxis, angioedema), paradoxical excitation, urinary retention, acute angle-closure glaucoma, severe sedation/confusion (elderly)

WATCH

Sedation and psychomotor impairment (driving/operating machinery), anticholinergic effects (dry mouth, constipation, urinary retention, blurred vision), paradoxical excitation in children/elderly, BPH/urinary retention symptoms

CDSCO approvedSchedule HJan AushadhiNPPA price-controlledATC R06AB04

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 1h · 0.5-1 h (oral); minutes (parenteral)
PEAK: 4h · 2-6 h (oral Cmax); 15-30 min (parenteral)
t½: 13.5h · 12-15 h (oral); 21-27 h (terminal)
DURATION: 6h · 4-8 h (Q4-6H dosing)

EXCRETION

~20-30% renal unchanged · hepatic CYP2D6 metabolism

route + CYP

INTERACTIONS

9 major

incl. contraindicated

PREGNANCY

Risk cannot be ruled out. Animal studies have not shown teratogenicity, but human data are limited. Use only if clearly needed and benefits outweigh risks. Generally considered relatively safe for short-term use in pregnancy, but avoid in third trimester near delivery (risk of neonatal withdrawal/irritability).

FDA category + note

Top interactionssee all 9 →

Monoamine Oxidase InhibitorsContraindicatedDatabaseKimi deep-research + Cla
AlcoholSevereDatabaseKimi deep-research + Cla
DextropropoxypheneSevereDatabaseDDInter
Other Cns DepressantsSevereDatabaseKimi deep-research + Cla

Available in India

66 branded formulations and 2,049 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Chlorpheniramine is a first-generation alkylamine antihistamine that competitively antagonizes histamine H1 receptors on target cells. By blocking histamine binding, it prevents histamine-mediated effects including vasodilation, increased vascular permeability, itching, and bronchoconstriction. Unlike second-generation antihistamines, chlorpheniramine readily crosses the blood-brain barrier and has significant anticholinergic properties, producing sedative, antiemetic, and anti-motion sickness effects.

Indications

Symptomatic relief of allergic rhinitis (seasonal and perennial)Symptomatic relief of urticaria and angioedemaAllergic conjunctivitis (adjunctive therapy)Pruritus due to allergic conditionsCommon cold (symptomatic relief of rhinorrhea and sneezing)Adjunctive treatment of anaphylaxis and anaphylactoid reactions (with epinephrine and corticosteroids)Prevention and treatment of allergic reactions to blood products and radiocontrast mediaMild allergic reactions to insect bites and stings

Dosing

Adult: Oral: 4 mg every 4-6 hours as needed. Maximum 24 mg/day. Parenteral (IM/IV/SC): 10-20 mg (typically 10 mg) as a single dose for severe allergic reactions, usually in conjunction with epinephrine.
Pediatric: Oral: 2-5 years: 1 mg every 4-6 hours (max 6 mg/day). 6-11 years: 2 mg every 4-6 hours (max 12 mg/day). ≥12 years: Adult dosing. Parenteral (severe reactions): 0.25-0.5 mg/kg/dose IV/IM/SC (max 10 mg/dose). Not recommended for children <2 years.
Renal adjustment: Use with caution in severe renal impairment (CrCl <30 mL/min or eGFR <30). Consider dose reduction of 50% or increased dosing interval to every 8-12 hours to avoid accumulation and increased anticholinergic/CNS side effects. Monitor for excessive sedation and urinary retention.
Hepatic adjustment: Use with caution in patients with hepatic impairment. Dose reduction may be necessary, starting with lower doses and monitoring for increased side effects (sedation, confusion, anticholinergic effects).
Geriatric: Start with 2 mg every 4-6 hours (half the usual adult dose) due to increased sensitivity to anticholinergic effects, sedation, and risk of falls. Maximum 12 mg/day. Monitor for confusion, urinary retention, constipation, and dry mouth.
Max dose: Oral: 24 mg/day (adults); 12 mg/day (geriatric); 12 mg/day (children 6-11 years); 6 mg/day (children 2-5 years). Parenteral: 20 mg/dose; 40 mg/day (adults)

Pharmacokinetics

Onset

30-60 minutes after oral administration; parenteral: rapid (within minutes).

Peak effect

Oral: 2-6 hours (Cmax); parenteral: 15-30 minutes.

Duration

4-8 hours (supports Q4-6H dosing); may be prolonged in elderly and patients with renal/hepatic impairment.

Half-life

12-15 hours (oral dosing in healthy adults); terminal elimination half-life 21-27 hours. Prolonged in elderly and renal impairment.

Bioavailability

Approximately 25-34% (oral; due to extensive first-pass metabolism).

Protein binding

Approximately 69-72% (primarily to albumin).

Metabolism

Extensively metabolized in the liver primarily via CYP2D6 (N-demethylation) to desmethylchlorpheniramine (active metabolite) and didesmethylchlorpheniramine. CYP2D6 poor metabolizers may have higher plasma concentrations and increased sedation.

Excretion

Primarily renal: mainly as unchanged drug and metabolites. Approximately 20-30% excreted unchanged in urine. Fecal excretion accounts for a small proportion. Renal impairment prolongs elimination.

Contraindications

Hypersensitivity to chlorpheniramine, other antihistamines, or any component of the formulation
Acute asthma attack (antihistamines may dry and thicken bronchial secretions, worsening airway obstruction)
Narrow-angle glaucoma (anticholinergic effects may increase intraocular pressure)
Lower respiratory tract symptoms (antihistamines may suppress cough reflex and thicken secretions)
Severe hypertension or severe coronary artery disease
Concurrent use with MAOIs or within 14 days of discontinuing MAOIs (risk of hypertensive crisis and anticholinergic toxicity)
Urinary retention due to bladder neck obstruction or prostatic hypertrophy (anticholinergic effects may worsen retention)
Pyloroduodenal obstruction
Stenosing peptic ulcer
Newborn and premature infants

Side effects

Common

Drowsiness/sedation (most common; dose-related)Dry mouthDizzinessBlurred vision (anticholinergic effect)Constipation (anticholinergic effect)Urinary retention (anticholinergic effect)HeadacheNauseaFatigueThickening of bronchial secretions

Serious

Paradoxical excitation (especially in children and elderly — hyperactivity, irritability, insomnia, hallucinations)
Seizures (rare; may occur with overdose or in patients with seizure disorders)
Arrhythmias (rare; tachycardia, palpitations, especially with overdose)
Severe hypersensitivity reactions (anaphylaxis, angioedema, severe skin reactions)
Blood dyscrasias (agranulocytosis, hemolytic anemia — very rare)
Hepatotoxicity (rare)
Acute angle-closure glaucoma (in patients with narrow-angle glaucoma)
Urinary retention requiring catheterization

Pregnancy & lactation

Pregnancy

Lactation

Chlorpheniramine is excreted in breast milk in small amounts. May cause drowsiness or irritability in the breastfed infant and may decrease milk supply due to anticholinergic effects. Use with caution; consider alternative antihistamines (e.g., loratadine, cetirizine) which are preferred during breastfeeding. If used, monitor infant for sedation, poor feeding, and irritability.

Drug interactions

Monoamine Oxidase Inhibitors

Contraindicated

Database

MAOIs inhibit the metabolism of antihistamines and potentiate their anticholinergic and CNS effects. Concurrent use can cause hypertensive crisis (due to potentiation of sympathomimetic amines), severe anticholinergic toxicity (hyperpyrexia, urinary retention, delirium), and respiratory depression. Fatalities have been reported.

CONTRAINDICATED. Do not use chlorpheniramine within 14 days of discontinuing an MAOI. If antihistamine therapy is needed, consider second-generation antihistamines (loratadine, cetirizine) which have fewer interactions with MAOIs.

Source: Kimi deep-research + Cla

Alcohol

Severe

Database

Additive CNS depression. Chlorpheniramine is a first-generation antihistamine with significant sedative properties. Alcohol potentiates these effects, causing excessive drowsiness, impaired judgment, respiratory depression, and increased risk of accidents and falls.

Advise complete abstinence from alcohol while taking chlorpheniramine. If alcohol is consumed, patient should avoid driving or operating machinery. Monitor for excessive sedation, especially in elderly patients.

Source: Kimi deep-research + Cla

Dextropropoxyphene

Severe

Database

Drug interaction classified as: synergy, metabolism

Source: DDInter

Other Cns Depressants

Severe

Database

Additive CNS depression. Concurrent use produces profound sedation, impaired cognition, respiratory depression (especially with opioids/benzodiazepines), hypotension, and increased risk of falls and accidents. Risk is highest in elderly patients.

Avoid concurrent use if possible. If combination is necessary, use lowest effective doses of both agents. Monitor respiratory rate, level of consciousness, and blood pressure. Consider non-sedating alternatives (e.g., cetirizine instead of chlorpheniramine).

Source: Kimi deep-research + Cla

Potassium Chloride

Severe

Database

Drug interaction classified as: absorption.

Source: DDInter

Potassium Citrate

Severe

Database

Drug interaction classified as: synergy

Source: DDInter

Sodium Oxybate