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Interaction of sulphinpyrazone with warfarin
European Journal of Clinical Pharmacology
|January 1, 1982
Summary
Sulphinpyrazone significantly increased the anticoagulant effect of warfarin, necessitating a 46% dose reduction in patients. This interaction, likely due to altered warfarin metabolism, resolved upon discontinuing sulphinpyrazone.
Area of Science:
- Pharmacology
- Drug Interactions
- Clinical Pharmacy
Background:
- Warfarin is a widely used anticoagulant.
- Understanding drug interactions with warfarin is crucial for patient safety.
- Sulphinpyrazone is a uricosuric agent with potential drug interaction properties.
Purpose of the Study:
- To investigate the effect of sulphinpyrazone on the anticoagulant response in patients taking warfarin.
- To determine the clinical significance and potential mechanism of this drug interaction.
Main Methods:
- A study involving five patients on long-term warfarin therapy.
- Monitoring of prothrombin (PT) ratio and warfarin dosage during sulphinpyrazone administration and cessation.
- In vitro assessment of warfarin protein binding and free fraction.
Main Results:
- Sulphinpyrazone administration led to a rapid increase in PT ratio in all patients.
- Warfarin dose requirements decreased by a mean of 46% to maintain therapeutic PT ratios.
- Warfarin protein binding and free fraction were not affected by sulphinpyrazone.
- Plasma warfarin concentrations were not altered when adjusted for dose.
- Effects reversed upon discontinuation of sulphinpyrazone.
Conclusions:
- Sulphinpyrazone significantly potentiates the anticoagulant effect of warfarin.
- The interaction is likely due to a stereoselective effect on warfarin metabolism.
- Clinical monitoring and warfarin dose adjustment are necessary when co-administering sulphinpyrazone.