II. Indications
- Parkinsonism (Idiopathic, Drug-Induced)
III. Contraindications
- Narrow Angle Glaucoma
- Acute Bowel Obstruction
- Megacolon
- Elderly (relative)
- On Beer's List, due to risk of Delirium, pscyhosis, Fall Risk
IV. Mechanism
- Centrally acting Muscarinic Antagonist
- Decreases imbalance of Acetylcholine to Dopamine ratio within corpus striatum (Basal Ganglia)
V. Dosing: Parkinsonism
- Start 1 mg orally daily
- May titrate dose by 2 mg/day weekly
- Target 6 to 10 mg/day orally divided three to four times daily
- Maximum: 15 mg/day divided 3-4 times daily
VI. Adverse Effects
- Anticholinergic Symptoms (Dry Mouth, Constipation, Urinary Retention, altered mentation)
- Pregnancy Category C
- Unknown safety in Lactation
- Withdrawal symptoms with severe increase in Parkinsonism symptoms
- Titrate medication off without abruptly stopping
VII. Resources
- Trihexyphenidyl (DailyMed)
VIII. References
- (2021) Med Lett Drugs Ther 63(1618): 25-32
- Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 46-7
- Hamilton (2020) Tarascon Pocket Pharmacopoeia
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Related Studies
| trihexyphenidyl (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
| TRIHEXYPHENIDYL 2 MG TABLET | Generic | $0.06 each |
| TRIHEXYPHENIDYL 2 MG/5 ML SOLN | Generic | $0.07 per ml |
| TRIHEXYPHENIDYL 5 MG TABLET | Generic | $0.10 each |