Pacitane (trihexyphenidyl)

# Pacitane (trihexyphenidyl) ## Overview Trihexyphenidyl is an anticholinergic medication used to treat symptoms of Parkinson's disease. ## Primary Indications * Adjunctive treatment of Parkinson's disease (especially tremor and rigidity). * Drug-induced extrapyramidal symptoms (EPS). ## Adult Dosing * **Parkinson's Disease:** Start with 1 mg orally once daily. Increase gradually based on response and tolerance. Usual maintenance dose is 5-15 mg orally daily, divided into 3-4 doses. Maximum dose is typically 15 mg orally daily. * **Drug-Induced EPS:** Start with 1 mg orally once daily. Increase gradually. Usual dose is 5-15 mg orally daily, divided into 3-4 doses. ## Pediatric Dosing Dosing in pediatric patients is not well-established and should be based on physician judgment and specific clinical circumstances. ## Dose Adjustments * **Hepatic Impairment:** Use with caution. No specific dose adjustments are established; titrate slowly and monitor closely. * **Renal Impairment:** Use with caution. No specific dose adjustments are established; titrate slowly and monitor closely. ## Contraindications * Hypersensitivity to trihexyphenidyl or any component of the formulation. * Glaucoma (especially narrow-angle). * Myasthenia gravis. * Conditions that may be aggravated by anticholinergic effects (e.g., certain cardiac conditions, prostatic hypertrophy, bowel obstruction). ## Adverse Effects Common adverse effects include dry mouth, blurred vision, constipation, urinary retention, drowsiness, dizziness, confusion, nervousness, nausea, and vomiting. Anticholinergic "toxic-line" symptoms (e.g., hyperthermia, dilated pupils, flushed skin, tachycardia, delirium) can occur, especially at higher doses. ## Key Drug Interactions * **Other Anticholinergic Agents:** Additive anticholinergic effects increase the risk of adverse events. * **CNS Depressants (e.g., alcohol, opioids, benzodiazepines):** Increased sedation and CNS depression. * **MAO Inhibitors:** May potentiate anticholinergic effects. * **Potassium Chloride (especially in slow-release formulations):** Anticholinergics can delay gastric emptying, potentially increasing the risk of gastrointestinal ulceration with slow-release potassium chloride. ## Monitoring * Monitor for signs and symptoms of anticholinergic toxicity. * Assess for improvement in Parkinsonian symptoms or EPS. * Monitor for constipation and urinary retention. * Regularly assess for cognitive changes, especially in elderly patients. ## Clinical Pearls * Trihexyphenidyl is generally less effective for Parkinsonian rigidity and bradykinesia than for tremor. * It is often more effective in young patients with postencephalitic Parkinsonism and for drug-induced EPS. * Administer with meals or after meals to minimize gastrointestinal upset. * Tapering of the dose is recommended when discontinuing to avoid withdrawal symptoms. *** *Disclaimer: This information is intended for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and a qualified healthcare professional for any medical decisions.*