CHOLOROHISTOL 4/MG TAB 20/TAB

Indications

Approved Uses

Symptomatic relief of allergic conditions such as allergic rhinitis (hay fever), urticaria/pruritus and other histamine‑mediated allergy symptoms (e.g., sneezing, runny nose, itchy/watery eyes); may also be used for symptomatic relief of common cold symptoms where histamine contributes.

Off-Label Uses

Occasionally used for short‑term nighttime sedation as part of multi‑symptom cold/allergy regimens; not a preferred agent for anxiety/insomnia, and it is not a standard therapy for nausea/vomiting or motion sickness compared with other first‑generation antihistamines.

Dosage & Administration

Dosing by Condition

Adults and adolescents ≥12 years: 4 mg orally every 4-6 hours as needed; maximum 24 mg/day (6 tablets/day).

Initial Dose

4 mg every 4-6 hours.

Maintenance Dose

4 mg every 4-6 hours as needed.

Maximum Dose

24 mg per 24 hours.

Children's Dosage

Children 6 to under 12 years: 2 mg every 4-6 hours, not to exceed 12 mg in 24 hours. Children 2 to under 6 years: 1 mg every 4-6 hours, not to exceed 6 mg in 24 hours (only under medical supervision). Not recommended for children under 2 years.

Dose Adjustment Notes

Use caution in older adults (greater sensitivity to sedation/anticholinergic effects) and consider lower doses; use with caution in hepatic impairment and in severe renal impairment due to prolonged effects.

How to Take

Swallow the immediate-release 4 mg tablet with water; may be taken with or without food. Do not exceed recommended dosing; avoid alcohol and other sedatives due to additive drowsiness.

Side Effects

Common Side Effects

Drowsiness/sedation, dizziness, dry mouth (and other anticholinergic effects such as dry nose/throat), blurred vision, constipation, urinary retention; thickened bronchial secretions/chest congestion can occur.

Side Effect Frequency

Common: sedation/drowsiness, dizziness, dry mouth, blurred vision, constipation; Less common/uncommon: confusion or paradoxical excitation (especially in children/elderly), nervousness/irritability, urinary retention/difficulty urinating, palpitations; Rare: seizures, arrhythmias, severe hypersensitivity reactions, blood dyscrasias.

Safety & Warnings

Contraindications

Hypersensitivity to chlorpheniramine; glaucoma; trouble urinating due to enlarged prostate; breathing problem such as emphysema or chronic bronchitis.

Warnings & Precautions

May cause significant drowsiness/impairment-avoid driving/alcohol/CNS depressants; caution in elderly (falls, confusion, anticholinergic burden); caution/avoid in asthma/COPD or thick secretions; caution in glaucoma, prostatic hypertrophy/urinary retention, cardiovascular disease/hypertension, hyperthyroidism, seizure disorders; paradoxical excitation may occur in children; avoid use with MAOIs within 14 days.

Age Restriction

Do not use in children <2 years; for ages 2-5 use only on a doctor’s advice; ≥6 years may use per label dosing.

Driving Warning

May Cause Drowsiness

Drug Interactions

Drug Interactions

MAOIs (contraindicated/avoid within 14 days-enhanced/prolonged anticholinergic/CNS effects); alcohol and other CNS depressants (additive sedation/psychomotor impairment); other anticholinergics incl. TCAs/antipsychotics (additive anticholinergic toxicity); phenytoin (possible increased phenytoin levels/toxicity-monitor).

Interaction Severity

MAJOR: Concomitant MAO inhibitors (or within 14 days) may intensify/prolong anticholinergic/CNS effects-avoid/contraindicated. MODERATE: Alcohol, opioids, benzodiazepines and other CNS depressants (additive sedation/respiratory depression risk); other anticholinergics and tricyclic antidepressants (additive anticholinergic effects).

Food Interaction

No restriction.

Alcohol Interaction

Avoid

Special Populations

Pregnancy

FDA Pregnancy Category B

Breastfeeding

Caution

Children

Children 6 to under 12 years: 2 mg every 4-6 hours, not to exceed 12 mg in 24 hours. Children 2 to under 6 years: 1 mg every 4-6 hours, not to exceed 6 mg in 24 hours (only under medical supervision). Not recommended for children under 2 years.

Storage & Patient Advice

Stopping the Medicine

Safe to stop anytime; no tapering required

Overdose

Symptoms: marked sedation or paradoxical excitation (esp. children), anticholinergic toxicity (mydriasis, dry mouth, flushing, hyperthermia, tachycardia, urinary retention), hallucinations/delirium, seizures, arrhythmias, coma; Management: urgent medical care/poison center, supportive care, airway/ventilation, benzodiazepines for seizures, activated charcoal if appropriate (early), cardiac/temperature monitoring.

Patient Counseling

May cause drowsiness-avoid driving/operating machinery until effects are known; avoid alcohol and other sedatives. Take 1 tablet (4 mg) every 4-6 hours as needed; do not exceed 6 tablets (24 mg) in 24 hours. Use caution/seek advice if you have glaucoma, prostate enlargement/urinary retention, or are elderly; seek medical advice if symptoms persist or worsen.

Monitoring Requirements

No routine monitoring required for short-term use; monitor for anticholinergic effects in elderly

Pharmacology

Mechanism of Action

First‑generation antihistamine that competitively antagonizes peripheral H1 receptors, reducing histamine‑mediated symptoms; also has clinically relevant anticholinergic (muscarinic‑blocking) and sedative CNS effects.

Duration of Effect

4-6 hours.

Half-Life

Approximately 12-43 hours (often cited mean around ~20-24 hours in adults).

Excretion

Primarily renal excretion (urine) as metabolites and some unchanged drug.

Protein Binding

Approximately 70% (about 69-72%).

Product Information

Available Dosage Forms

For chlorpheniramine maleate in general: immediate‑release tablets, oral liquid (syrup/solution), and extended‑release tablets/capsules; injectable forms exist in some markets but are not universal.

Composition per Dose

Each tablet: 4mg chlorpheniramine maleate

Generic Availability

Yes

OTC Alternatives

Second‑generation antihistamines (e.g., loratadine, cetirizine, fexofenadine) for less sedation; other sedating antihistamines (e.g., diphenhydramine) are alternatives but generally cause more drowsiness.

Symptom Target

Allergy, Runny Nose

Sedating

Yes

Reviewed by Al Mujtama Pharmacy Medical Review Team. Last reviewed 14-06-2026