BENZHEXOL (TRIHEXYPHENIDYL)

Antimuscarinic that reduces extra-pyramidal Parkinson-like symptoms caused by antipsychotic medicines. The symptoms include movement problems, stiffness, and shaking.

Dosage Forms

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Tablet

2 mg

Syrup

5 mg/5ml

Uses

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  • Extra-pyramidal symptoms caused by antipsychotic medicines, such as chlorpromazine and haloperidol

Dose and Duration

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Medicine-induced extra-pyramidal side-effects
Adult: initially 2 mg every 12 hours, increased by 2 mg every 3‒5 days according to response; usual maintenance dose is 5‒15 mg in every 8 or 6 hours daily.

Contraindications

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  • Glaucoma
  • Urinary and prostate problems
  • Muscle weakness and fatigue
  • Intestinal obstruction
  • Liver disease
  • Kidney disease
  • Involuntary, repetitive body movements (tardive dyskinesia)

Side Effects

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  • Constipation, dry mouth, stomach upset
  • Blurred vision
  • Urinary retention
  • Problems with producing and understanding language, awareness, reasoning, decision-making, and judgement

Interactions

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  • Other antimuscarinic medicines e.g. atropine (increased risk of side effects)
  • Antihistamines (increased risk of side effects)

Patient instructions

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  • May impair ability to perform skilled tasks, such as driving or operating machinery

Pregnancy

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  • Do not use

Breastfeeding

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  • Do not use

⚠️ Caution

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  • Should not be given routinely to patients receiving antipsychotic medicines in the absence of Parkinson-like side effects
  • Use lower doses in elderly; higher doses cause confusion
  • Avoid use of benzhexol for Parkinson’s disease as it can cause toxicity in elderly and make dementia worse