Bleeding complications in a patient after the unexpected interaction between valproic acid and phenprocoumon

Autor: André Wieringa, Helle-Brit Fiebrich, Fleur van Gelder, Abraham J. Valkenburg, Jan Gerard Maring, Elise J. Smolders
Rok vydání: 2023
Předmět:
Zdroj: Current Drug Safety. 18
ISSN: 1574-8863
DOI: 10.2174/1574886318666230310104322
Popis: Background: Phenprocoumon is a vitamin K antagonist that is widely prescribed in Europe and Latin America for the prophylaxis and treatment of thromboembolic events Case presentation: A 90-year-old female was admitted to our hospital with tonic-clonic seizures, possibly due to dementia syndrome. Discussion: Valproic acid (VPA) was prescribed for the treatment of seizures. VPA is an inhibitor of cytochrome P450 (CYP) 2C9 enzymes. A pharmacokinetic interaction with phenprocoumon occurred, which is a substrate for CYP2C9 enzymes. The interaction resulted in a strong INR increase and subsequent clinically relevant bleeding in our patient. Valproic acid is not specifically mentioned in the phenprocoumon drug label as a CYP2C9 inhibitor, and in the Dutch medication surveillance database, no medication alert is shown when prescribing this combination, and no interaction with phenprocoumon has been reported so far. Conclusion: When prescribing this combination, the prescriber should be warned and advised to intensify INR monitoring if the combination is to be continued.
Databáze: OpenAIRE