Drug General Information (ID: DDICU0R4QS)
Drug Name			Trihexyphenidyl		Drug Info		Levodopa		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antiparkinson Agents				Dopaminergic Antiparkinsonism Agents
Structure

Mechanism of Trihexyphenidyl-Levodopa Interaction (Severity Level: Moderate)
Altered gastrointestinal dynamics Click to Show/Hide Mechanism Graph
Drug Name		Trihexyphenidyl				Levodopa
Mechanism		Delayed gastric emptying				Absorption affected by delayed gastric emptying
Key Mechanism Factor 1
		Factor Name		Gastrointestinal Motility
		Factor Description		Gastrointestinal motility is an important factor in determining the absorption of orally administered drugs, and it controls the residence time of the drug in the digestive tract.
Mechanism Description		Altered absorption of Levodopa due to GI dynamics variation caused by Trihexyphenidyl

Recommended Action
Management		The dosage of both drugs may require reduction. The manufacturer recommends total daily trihexyphenidyl doses of 3 to 6 mg when given concurrently with levodopa. Patients should be monitored for symptom control and side effects.

References
1	Algeri S, Cerletti C, Curcio M, et al. "Effect of anticholinergic drugs on gastro-intestinal absorption of L-dopa in rats and man." Eur J Pharmacol 35 (1976): 293-9. [PMID: 1248506]
2	Product Information. Artane (trihexyphenidyl). Lederle Laboratories, Wayne, NJ.
3	Rivera-Calimlim L, Dujovne CA, Morgan JP, Lasagna L, Bianchine JR "Absorption and metabolism of L-dopa by the human stomach." Eur J Clin Invest 1 (1971): 313-20. [PMID: 5558777]