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    Prescription under medical supervision


    Therapeutic action

    • Anticholinergic antiparkinson drug


    • Second-line treatment of extrapyramidal reactions induced by antipsychotics

    Forms and strengths

    • 2 mg tablet


    • Adult: 2 mg once daily, then increase if necessary up to 2 mg 2 or 3 times daily (max. 12 mg daily)
    • Administer the lowest effective dose in elderly patients and do not exceed 10 mg daily.


    • As long as antipsychotic treatment lasts.

    Contra-indications, adverse effects, precautions

    • Do not administer to patients with closed-angle glaucoma, prostate disorders, gastrointestinal obstruction or atony.
    • Administer with caution and carefully monitor use in elderly patients (risk of mental confusion, hallucinations).
    • May cause: anticholinergic effects (dry mouth, constipation, blurred vision, tachycardia, disorders of micturition), confusion, hallucinations, memory loss.
    • Avoid or monitor combination with other anticholinergic drugs (atropine, amitriptyline, chlorpromazine, promethazine, etc.).
    • Pregnancy: re-evaluate whether the antipsychotic treatment is still necessary; if treatment is continued, administer trihexyphenidyl at the lowest effective dose; observe the neonate if the mother was under treatment in the 3rd trimester (risk of anticholinergic effects, e.g. tremors, abdominal distension).
    • Breast-feeding: if treatment is necessary, administer at the lowest effective dose and observe the child (risk of anticholinergic effects, e.g. tachycardia, constipation, thickening of bronchial secretions).


    • Take with meals.
    • Also comes in 2 mg extended-release capsule, administered once daily.
    • Trihexyphenidyl is also used in treatment of Parkinson’s disease.


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