1. Clinical & Scientific Overview
Hydroxyzine Hydrochloride & Promethazine Theoclate / Hydrochloride (TIP-MED-000183, Reference Code [9.19]) is classified under
Respiratory, Asthma, COPD & Allergy Medicines (Ch 09) as a First-Generation Lipophilic Histamine H1-Receptor Inverse Agonists & Central Anticholinergics (Schedule H | NLEM 2022).
Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug (To be sold by retail on the prescription of a Registered Medical Practitioner only — Drugs Rules 1945).
Representative Indian Market Examples (Edition 2.7 Ch 09 [9.19], p. 123): Hydroxyzine: Atarax (Dr. Reddy's), Hicope (Mankind). Promethazine: Phenergan (Abbott — HCl for allergy/sedation), Avomine (Abbott — Theoclate 25 mg for motion sickness/vertigo) — Strengths & Dosage Forms: Hydroxyzine Tablets: 10 mg, 25 mg; Syrup: 10 mg/5mL; Drops: 6 mg/mL. Promethazine HCl Tablets: 10 mg, 25 mg; Syrup: 5 mg/5mL; IM/IV: 25 mg/mL. Promethazine Theoclate (Avomine) Tablets: 25 mg
Hydroxyzine Tablets: 10 mg, 25 mg; Syrup: 10 mg/5mL; Drops: 6 mg/mL. Promethazine HCl Tablets: 10 mg, 25 mg; Syrup: 5 mg/5mL; IM/IV: 25 mg/mL. Promethazine Theoclate (Avomine) Tablets: 25 mg
3. Mechanism of Action & Pharmacodynamics
First-Generation Lipophilic Histamine H1-Receptor Inverse Agonists & Central Anticholinergics (Schedule H | NLEM 2022) acting on target receptor/enzyme pathways in Respiratory, Asthma, COPD & Allergy Medicines (Ch 09): clinical efficacy is mediated via First-Generation Lipophilic Histamine H1-Receptor Inverse Agonists & Central Anticholinergics (Schedule H | NLEM 2022) for Hydroxyzine: Severe nocturnal pruritus (urticaria, atopic eczema, uraemic/cholestatic pruritus) where night-time sedation helps break the itch–scratch cycle; short-term preoperative/acute anxiety. Promethazine: Motion sickness prophylaxis (Avomine 25 mg taken 1–2h before travel), acute vestibular vertigo, drug-induced acute dystonia.
4. Therapeutic Indications & Evidence-Supported Uses
- Hydroxyzine: Severe nocturnal pruritus (urticaria, atopic eczema, uraemic/cholestatic pruritus) where night-time sedation helps break the itch–scratch cycle
- short-term preoperative/acute anxiety
- Promethazine: Motion sickness prophylaxis (Avomine 25 mg taken 1–2h before travel), acute vestibular vertigo, drug-induced acute dystonia
🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.
5. Educational Dosage Context, Formulations & Administration
Educational Dosing & Regimen Summary: Hydroxyzine (Adults): Pruritus: 10–25 mg PO at BEDTIME (up to 25 mg TDS in young adults; Max 100 mg/day; Max 50 mg/day in elderly if ever used!). Promethazine: Allergy/Pruritus: 10–25 mg PO at bedtime; Motion Sickness (Avomine): 25 mg PO at bedtime on night before travel
Administration & Meal Timing: May be taken with or without food | At Bedtime (or 1–2h prior to travel for Avomine)
6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Renal: Halve Hydroxyzine dose if eGFR <=50 mL/min. Hepatic: Reduce Hydroxyzine daily dose by 33–50% in cirrhosis
Renal: Halve Hydroxyzine dose if eGFR <=50 mL/min. Hepatic: Reduce Hydroxyzine daily dose by 33–50% in cirrhosis
Renal: Halve Hydroxyzine dose if eGFR <=50 mL/min. Hepatic: Reduce Hydroxyzine daily dose by 33–50% in cirrhosis
7. Contraindications, Precautions & High-Risk Warnings
- CONTRAINDICATIONS & REGULATORY WARNINGS: (1) LASA ALERT: Atarax (Hydroxyzine 10/25 mg) vs. Atorva (Atorvastatin 10/20 mg) AND hydrOXYzine vs. hydrALAZINE! (2) Hydroxyzine carries an EMA/CDSCO QTc-Prolongation Warning — CONTRAINDICATED in congenital/acquired QTc prolongation or with other QTc-prolonging drugs! (3) Promethazine is STRICTLY CONTRAINDICATED in children <2 years of age (boxed warning: fatal respiratory depression & SIDS!) and in narrow-angle glaucoma or BPH urinary retention!
Key Clinical Precautions: Renal: Halve Hydroxyzine dose if eGFR <=50 mL/min. Hepatic: Reduce Hydroxyzine daily dose by 33–50% in cirrhosis
8. Adverse Effects Profile
- Marked daytime drowsiness/hangover sedation, dry mouth, blurred vision, constipation, urinary hesitancy, dizziness, paradoxical excitation in young children
- QTc prolongation and Torsades de Pointes (Hydroxyzine & Promethazine), acute angle-closure glaucoma, acute urinary retention in BPH, anticholinergic delirium/falls in elderly, fatal respiratory depression in infants <2 yr (Promethazine)
- Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.
9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions
- Additive QTc prolongation with Amiodarone, Sotalol, Moxifloxacin, Azithromycin/Clarithromycin, Ondansetron, Domperidone, Escitalopram, and Haloperidol (CONTRAINDICATED with Hydroxyzine!); additive CNS depression with Alcohol, Benzodiazepines, Opioids, and Pregabalin; additive Anticholinergic Burden (ACB Score = 3!) with Amitriptyline, Oxybutynin, and Trihexyphenidyl
10. Clinical Monitoring, Patient Counselling & Storage
Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.
Pharmacist Patient Counselling Points:
- Patient Counselling Checklist: FOUR CRITICAL COUNTER RULES: (1) Double-check 'Atarax' (itching tablet) vs 'Atorva' (cholesterol tablet); (2) Never give Phenergan syrup to a baby/toddler under 2 years old (can stop breathing during sleep!); (3) Causes heavy drowsiness — take only at bedtime and NEVER drive or ride a two-wheeler the next morning if groggy; (4) For daytime allergy, use non-drowsy Fexofenadine or Bilastine instead
- Meal & Clock Timing Instruction: May be taken with or without food (At Bedtime (or 1–2h prior to travel for Avomine))
- Missed Dose Protocol: PRN at bedtime
- Geriatric Dispensing Pearl: STRONGLY AVOID Hydroxyzine and Promethazine in older adults >=65 years (AGS Beers 2023 & STOPP v3: Potent Anticholinergic [ACB = 3] + QTc prolongation -> high risk of acute delirium, falls/hip fractures, and urinary retention)
Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Hydroxyzine Tablets: 10 mg, 25 mg; Syrup: 10 mg/5mL; Drops: 6 mg/mL. Promethazine HCl Tablets: 10 mg, 25 mg; Syrup: 5 mg/5mL; IM/IV: 25 mg/mL. Promethazine Theoclate (Avomine) Tablets: 25 mg
11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)
12. Authoritative References, Regulatory Sources & Editorial Disclaimer
Primary Compendial & Guideline Reference: Indian Pharmacist Desk Reference — Professional Edition 2.7 (2026–27) • Ch 09 [9.19] (p. 123)
Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)
Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: HANDBOOK_SOURCE_CONTENT
Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.
13. Related Reference Monographs, Educational Guides & Visual Concept
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