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MEDICINE MONOGRAPH CODE: [11.22]-CMP141 ID: TIP-MED-000411

Trihexyphenidyl (Benzhexol) Hydrochloride IP

Active Ingredient / Scientific Identity: Trihexyphenidyl • Class: First-Generation (Typical) Butyrophenone Antipsychotic (Potent Dopamine D2 Receptor Antagonist)

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THE INDIAN PHARMACIST — Educational Reference Sheet
Profile: Trihexyphenidyl (Benzhexol) Hydrochloride IP ([11.22]-CMP141 | ID: TIP-MED-000411) • Last Reviewed: 2026-11-10
Source URL: https://theindianpharmacist.com/medicine/11-22-cmp141-trihexyphenidyl-benzhexol-hydrochloride-ip/
Generic / Entity NameTrihexyphenidyl (Benzhexol) Hydrochloride IP ([11.22]-CMP141)
Verified Indian Brands / RefGeneric Compendial Entry (No Commercial Brand Claimed)
Pharmacological ClassFirst-Generation (Typical) Butyrophenone Antipsychotic (Potent Dopamine D2 Receptor Antago
Available Dosage FormsStandard approved strengths (refer to comparative context)
Regulatory ClassificationSchedule H Prescription Drug (To be sold by retail on the prescription of a Registere
Key Warning & Review DateRenal: No routine adjustment; use lower doses in elderly/uremic patients due to heightened extrapyramidal sensitivity. • Hepa
Reviewed: 2026-11-10
Safety Matrix:⚖️ Legal Status: Schedule H Prescription Drug (To be sold by retail o✔️ Standard Clinical Dispensing Precautions

1. Clinical & Scientific Overview

Trihexyphenidyl (Benzhexol) Hydrochloride IP (TIP-MED-000411, Reference Code [11.22]-CMP141) is classified under CNS & Psychiatric Medicines (Ch 11) as a First-Generation (Typical) Butyrophenone Antipsychotic (Potent Dopamine D2 Receptor Antagonist). 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).

Verified Indian Market Examples / Compendial Status:
Co-indexed per approved Author Decision DEC-07 (Option 7A; displaced HTML [11.23]). Central M1 anticholinergic (Pacitane 2 mg) for antipsychotic-induced acute dystonia and pseudoparkinsonism (EPS).
Co-indexed per approved Author Decision DEC-07 (Option 7A; displaced HTML [11.23]). Central M1 anticholinergic (Pacitane 2 mg) for antipsychotic-induced acute dystonia and pseudoparkinsonism (EPS).
Dosage Forms & Available Strengths:
Standard approved strengths (refer to comparative context)
Routes: Oral / Parenteral

3. Mechanism of Action & Pharmacodynamics

Co-indexed per approved Author Decision DEC-07 (Option 7A; displaced HTML [11.23]). Central M1 anticholinergic (Pacitane 2 mg) for antipsychotic-induced acute dystonia and pseudoparkinsonism (EPS).

4. Therapeutic Indications & Evidence-Supported Uses

  • Schizophrenia and acute psychoses
  • acute hyperactive delirium and severe behavioural agitation
  • Tourette syndrome and severe tics
  • intractable hiccups / palliative nausea

🇮🇳 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: Co-indexed per approved Author Decision DEC-07 (Option 7A; displaced HTML [11.23]). Central M1 anticholinergic (Pacitane 2 mg) for antipsychotic-induced acute dystonia and pseudoparkinsonism (EPS).

Administration & Meal Timing: See Administration & Counselling below. | Standard clinical schedule per indication.

6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment

Absorption & Disposition:
Comparative pharmacokinetic profile co-indexed under [11.22].
Metabolism & Biotransformation:
Renal: No routine adjustment; use lower doses in elderly/uremic patients due to heightened extrapyramidal sensitivity. • Hepatic: Metabolised in liver; reduce dose by 50% in severe hepatic impairment.
Elimination & Renal Adjustment:
Renal: No routine adjustment; use lower doses in elderly/uremic patients due to heightened extrapyramidal sensitivity. • Hepatic: Metabolised in liver; reduce dose by 50% in severe hepatic impairment.
Hepatic Impairment Considerations:
Renal: No routine adjustment; use lower doses in elderly/uremic patients due to heightened extrapyramidal sensitivity. • Hepatic: Metabolised in liver; reduce dose by 50% in severe hepatic impairment.

7. Contraindications, Precautions & High-Risk Warnings

Contraindications & Red-Flag Precautions:
  • Contraindications: Parkinson's disease, dementia with Lewy bodies, congenital long-QT syndrome, CNS depression/coma. • Precautions: High incidence of acute dystonia, akathisia, and drug-induced parkinsonism (keep Promethazine or Trihexyphenidyl/Procyclidine available); IV use (off-label in ICU) requires continuous ECG monitoring for Torsades de Pointes.

Key Clinical Precautions: Renal: No routine adjustment; use lower doses in elderly/uremic patients due to heightened extrapyramidal sensitivity. • Hepatic: Metabolised in liver; reduce dose by 50% in severe hepatic impairment.

8. Adverse Effects Profile

Common & Mechanism-Related Adverse Effects:
  • Extrapyramidal symptoms (acute oculogyric/neck dystonia, akathisia, rigidity, tremor), hyperprolactinaemia.
  • Neuroleptic malignant syndrome (hyperpyrexia, lead-pipe rigidity, high CPK), tardive dyskinesia, QT prolongation.
Serious / Dose-Limiting Adverse Effects:

    9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions

    • QT-prolonging drugs (Amiodarone, Ondansetron, Macrolides, Fluoroquinolones) -> Torsades de Pointes; Levodopa/Dopamine agonists -> mutual antagonism; Lithium -> encephalopathic syndrome at high doses

    10. Clinical Monitoring, Patient Counselling & Storage

    Clinical & Laboratory Monitoring: Monitor clinical parameters per parent class monograph [11.22].

    Pharmacist Patient Counselling Points:

    • Patient Counselling Checklist: Report muscle stiffness, restlessness, neck spasms, or high fever immediately; avoid abrupt discontinuation.
    • Meal & Clock Timing Instruction: See Administration & Counselling below. (Standard clinical schedule per indication.)
    • Missed Dose Protocol: Take as soon as remembered unless close to next scheduled dose; never double the dose.
    • Geriatric Dispensing Pearl: Schedule: Schedule H | NLEM 2022: Yes | Compendia: IP 2026 / NFI 7th Ed 2026 / NLEM 2022 / CDSCO Schedule H / BNF 90th Ed

    Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Tablet: 0.25 mg, 0.5 mg, 1.5 mg, 5 mg, 10 mg, 20 mg; Oral Drops: 2 mg/mL; Injection (Lactate): 5 mg/mL; Depot Injection (Decanoate): 50 mg/mL, 100 mg/mL.

    11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)

    THE 12-STEP ORAL DRUG JOURNEY THROUGH THE HUMAN BODY (LADME) Note: IV bolus enters Step 6 directly (F = 100%); Sublingual & Transdermal routes bypass Step 4–5 Portal First-Pass Metabolism 1. Oral Administration • Tablet / Capsule swallowed • Gastric emptying to duodenum pH 1.5–3.5 (Stomach) 2. Disintegration & Dissolution • Tablet breaks into granules • API dissolves in GI fluid Noyes-Whitney Dissolution Rate 3. GI Epithelial Absorption • Crosses intestinal villi • Passive / Active / P-gp efflux Small Intestine (Large Surface Area) 4. Portal Circulation • Mesenteric veins → Portal vein • Delivers blood to liver sinusoids Pre-systemic Venous Conduit 5. First-Pass Metabolism • Gut & hepatic CYP450 extraction • High: GTN, Propranolol, Morphine Determines Bioavailability (F = f_a × (1-E_H)) 6. Systemic Circulation • Hepatic vein → IVC → Heart • Unbound vs Albumin-bound drug Only FREE drug is active 7–8. Tissue Distribution (Vd) • Capillary permeation to organs • Blood-Brain & Placental barriers Vd = Dose / C_0 (L or L/kg) 9. Target Site of Action • Receptors (GPCR, Ion channel) • Enzymes & Carrier Transporters Pharmacodynamic Effect (E_max, EC50) 10. Hepatic Biotransformation • Phase I (CYP450 Oxidation/Hydrolysis) • Phase II (Glucuronidation/Sulfation) Converts lipophilic drug → hydrophilic metabolite 11. Renal & Biliary Elimination • Nephron: Filtration + Secretion − Reabsorption • Biliary excretion & Enterohepatic recycling Total Clearance CL_tot = CL_renal + CL_hepatic 12. Excretion from the Body • Urine (Primary polar metabolite route) • Bile/Faeces, Expired Air, Sweat, Milk Elimination Half-Life t1/2 = (0.693 × Vd) / CL
    svg-v339-01-adme-12-step-journey — 8.1 Complete 12-Step Journey of an Orally Administered Drug (ADME): Figure 8.1: The 12-step physiological journey of a typical orally administered solid dosage form through Liberation, Absorption, Distribution, Metabolism, and Excretion (LADME). Note: Parenteral (IV), sublingual, and inhalational routes bypass gastrointestinal absorption and/or hepatic first-pass metabolism.

    12. Authoritative References, Regulatory Sources & Editorial Disclaimer

    Primary Compendial & Guideline Reference: Indian Pharmacopoeia (IP 2022) • NFI • CDSCO

    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: VERIFIED_EDUCATIONAL_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.

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    Educational Reference Notice: This printout from THE INDIAN PHARMACIST (https://theindianpharmacist.com/medicine/11-22-cmp141-trihexyphenidyl-benzhexol-hydrochloride-ip/, Last Reviewed: 2026-11-10) is an educational reference sheet for students and healthcare learners. It is NOT an official prescribing guideline or patient-specific treatment order.