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# Pacitane (Trihexyphenidyl)
## Overview
Trihexyphenidyl is an antispasmodic agent and a synthetic anticholinergic drug used primarily to manage Parkinsonism and extrapyramidal symptoms (EPS) induced by antipsychotics.
## Primary Indications
* Adjunctive therapy in all forms of Parkinsonism (postencephalitic, arteriosclerotic, and idiopathic).
* Control of extrapyramidal disorders induced by CNS drugs (e.g., phenothiazines, thioxanthenes, butyrophenones).
## Adult Dosing
* **Parkinsonism:** Initially 1 mg orally on day 1. Increase by 2 mg daily at 3- to 5-day intervals. Usual maintenance: 6–10 mg/day in 3–4 divided doses. Max: 15 mg/day.
* **Drug-Induced Extrapyramidal Symptoms:** Initially 1 mg daily. Titrate upward as needed. Usual range: 5–15 mg/day in divided doses.
## Pediatric Dosing
* **Safety/Efficacy:** Not well-established in children. Use caution. If required, clinical literature suggests starting at 1 mg daily. Titrate slowly based on response and tolerance. Dose should be individualized based on institutional or specialist protocol.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No formal standardized adjustment guidelines exist; exercise caution and monitor for increased CNS sensitivity.
* **Geriatric:** Increased susceptibility to anticholinergic side effects (confusion, urinary retention, constipation). Start at lowest possible dose and titrate cautiously.
## Contraindications
* Hypersensitivity to trihexyphenidyl.
* Narrow-angle glaucoma.
* Pyloric or duodenal obstruction, or stenosing peptic ulcers.
* Prostatic hypertrophy or bladder neck obstruction.
* Myasthenia gravis.
* Megacolon.
## Adverse Effects
* **Common:** Dry mouth, blurred vision, dizziness, nervousness, nausea, constipation.
* **Serious:** Tachycardia, urinary retention, cognitive impairment (hallucinations, confusion, memory impairment), hyperthermia, and precipitation of narrow-angle glaucoma.
## Key Drug Interactions
* **Anticholinergics:** Additive anticholinergic effects (e.g., antihistamines, TCAs).
* **Antipsychotics:** May decrease effectiveness of antipsychotic therapy or increase risk of anticholinergic toxicity.
* **Metoclopramide/Domperidone:** Antagonizes the GI motility effects of these prokinetic agents.
## Monitoring
* Monitor for neurological status (mental status changes).
* Assess for baseline and ongoing intraocular pressure in patients at risk for glaucoma.
* Observe for signs of urinary retention and constipation.
## Clinical Pearls
* Administering after meals may reduce gastric distress.
* The drug should be discontinued gradually to avoid precipitating acute extrapyramidal symptoms.
* Advise patients regarding impaired ability to perform tasks requiring mental alertness; avoid driving if drowsiness/blurred vision occurs.
* Avoid alcohol and other CNS depressants due to additive sedation.
* **Beers Criteria:** Generally discouraged in geriatric populations due to high risk of adverse cognitive and systemic effects.
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*Disclaimer: This information is for educational purposes only. Prescribing practices may vary based on local protocols and clinical guidelines. Always consult current institutional drug databases and individual drug monographs before prescribing or administering medication.*
