Drug General Information (ID: DDIR578Q4B)
Drug Name			Valproic acid		Drug Info		Cholestyramine		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Anticonvulsants				Bile Acid Sequestrants
Structure

Mechanism of Valproic acid-Cholestyramine Interaction (Severity Level: Moderate)
Complex formation Click to Show/Hide Mechanism Graph
Drug Name		Valproic acid				Cholestyramine
Mechanism		Binds to anion exchange resin/polymer				Anion exchange resin/polymer
Key Mechanism Factor 1
		Factor Name		Chelation
		Factor Description		Chelation is a direct drug interaction that usually involves the formation of dimers or trimers, resulting in larger complexes and poorer absorption.
Mechanism Description		Decreased absorption of Cholestyramine due to formation of complexes caused by Valproic acid

Recommended Action
Management		To minimize potential for interaction, valproic acid and cholestyramine should be administered at least 3 hours apart. Patients should be monitored for clinical and laboratory evidence of altered valproate efficacy, and the dosage adjusted if necessary. It is not known whether these precautions are applicable to extended-release valproic acid or divalproex formulations.

References
1	Cerner Multum, Inc. "UK Summary of Product Characteristics.".
2	Malloy MJ, Ravis WR, Pennell AT, Diskin CJ "Effect of cholestyramine resin on single dose valproate pharmacokinetics." Int J Clin Pharmacol Ther 34 (1996): 208-11. [PMID: 8738857]
3	Product Information. Depakene (valproic acid). Abbott Pharmaceutical, Abbott Park, IL.