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RESPIRATORY SYSTEM › ANTIHISTAMINES FOR SYSTEMIC USE › ANTIHISTAMINES FOR SYSTEMIC USE › Piperazine derivatives
chlorcyclizine
R06AE04
Forms & Strengths
- Tablets 5 mg
- Oral solution 5 mg/5 mL
Adult Dosing
- 5–10 mg orally 3–4 times daily; max 40 mg/day
- 5 mg 30 min before travel for motion sickness; repeat q6 h if needed
Indications
- Allergic rhinitis and conjunctivitis
- Urticaria and pruritus
- Motion‑sickness prophylaxis
- Mild postoperative nausea
Mechanism of Action
- Competitive antagonist at peripheral and central H1 receptors
- Inverse agonist activity reduces histamine‑mediated vasodilation and itching
- Penetrates blood‑brain barrier → sedation and anticholinergic effects
Contraindications
- Known hypersensitivity to chlorcyclizine or piperazine antihistamines
- Severe narrow‑angle glaucoma
- Severe hepatic impairment
Adverse Reactions
- Sedation, somnolence, fatigue
- Dry mouth, blurred vision, constipation, urinary retention (anticholinergic)
- Dizziness, headache
- Tachycardia, palpitations
- Rare extrapyramidal symptoms
Drug Interactions
- Additive CNS depression with alcohol, opioids, benzodiazepines, other antihistamines
- Increased anticholinergic load with anticholinergic drugs
- CYP3A4 inhibitors may raise chlorcyclizine levels
- Concurrent QT‑prolonging agents may increase arrhythmia risk
Curated Content: Needs Vetting Before Put to Clinical Use