Formulary
Trihexyphenidyl hydrochloride: Indications, Dosing, Side Effects and Interactions
Trihexyphenidyl exerts its effects by reducing the effects of the relative central cholinergic excess that occurs as a result of dopamine deficiency.
MedNext Academy | 3 min read
Trihexyphenidyl hydrochloride: Indications, Dosing, Side Effects and Interactions
Trihexyphenidyl exerts its effects by reducing the effects of the relative central cholinergic excess that occurs as a result of dopamine deficiency.
Drug action
Trihexyphenidyl exerts its effects by reducing the effects of the relative central cholinergic excess that occurs as a result of dopamine deficiency.
Indications and dose
**Parkinson's disease (if used in combination with co-careldopa or co-beneldopa)**
- **Adult** (By Mouth): Maintenance 2-6 mg daily in divided doses, use not recommended because of toxicity in the elderly and the risk of aggravating dementia.
**Parkinsonism,Drug-induced extrapyramidal symptoms (but not tardive dyskinesia)**
- **Adult** (By Mouth): 1 mg daily, then increased in steps of 2 mg every 3-5 days, adjusted according to response; maintenance 5-15 mg daily in 3-4 divided doses, not recommended for use in Parkinson's disease because of toxicity in the elderly and the risk of aggravating dementia; maximum 20 mg per day.
- **Elderly** (By Mouth): Lower end of range preferable, not recommended for use in Parkinson's disease because of toxicity in the elderly and the risk of aggravating dementia.
**Dystonia for trihexyphenidyl hydrochloride**
- **Child 3 months-17 years** (By mouth): Initially 1-2 mg daily in 1-2 divided doses, then increased in steps of 1 mg every 3-7 days, dose to be adjusted according to response and side-effects; maximum 2 mg/kg per day.
Cautions
Cardiovascular disease; elderly; gastro-intestinal obstruction; hypertension; liable to abuse; prostatic hypertrophy; psychotic disorders; pyrexia; those susceptible to angle-closure glaucoma
Contraindications
Myasthenia gravis
Side effects
Frequency not known Anxiety; bronchial secretion decreased; confusion; constipation; delusions; dizziness; dry mouth; dysphagia; euphoric mood; fever; flushing; hallucination; insomnia; memory loss; myasthenia gravis aggravated; mydriasis; nausea; skin reactions; tachycardia; thirst; urinary disorders; vision disorders; vomiting
Interactions
**Other interactions (6):**
- Extra care should be taken when trihexyphenidyl is given concomitantly with phenothiazines, clozapine, antihistamines, disopyramide, nefopam and amantadine because of the possibility of increased...
- Synergy has been reported between trihexyphenidyl and tricyclic antidepressants, probably because of an additive effect at the receptor site.
- Monoamine oxidase inhibitors can interact with concurrently administered anticholinergic agents including trihexyphenidyl.
- In general, anticholinergic agents should be used with caution in patients who are receiving tricyclic antidepressants or monoamine oxidase inhibitors.
- Trihexyphenidyl may be antagonistic with the actions of metoclopramide and domperidone on gastro-intestinal function.
- The absorption of levodopa may possibly be reduced when used in conjunction with trihexyphenidyl.
Pregnancy
Use only if potential benefit outweighs risk.
Breast feeding
Avoid.
Hepatic impairment
Manufacturer advises caution.
Renal impairment
Use with caution. M
Medicinal forms
Solution,Tablet,Solution
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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