Key result
Stopping rifampin and isoniazid requires a ~50% warfarin dose reduction due to decreased clearance.
Why the study?
The interaction between rifampin and warfarin includes a potentiating influence on warfarin effect during coadministration with isoniazid that is not fully understood.
Does the coadministration of rifampin and isoniazid alter the pharmacokinetics and pharmacodynamics of warfarin?
Comparison
Coadministration of rifampin and isoniazid with warfarin vs warfarin therapy after cessation of rifampin and isoniazid
Design
Case report
Authors
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May require warfarin dose titration after rifampin-isoniazid cessation; leaves open need for prospective interaction studies.
Case Report (n=1)
Does the coadministration of rifampin and isoniazid alter the pharmacokinetics and pharmacodynamics of warfarin?
Absolute Event Rate: 15.2% vs 4.2%
Rifampin appears to exert a potentiating pharmacodynamic effect on warfarin in addition to its known pharmacokinetic effect of increasing warfarin clearance.
Almog et al. (1988) conducted a case report in Patient on warfarin therapy (n=1). Rifampin and isoniazid vs. Cessation of rifampin and isoniazid was evaluated on Warfarin fractional clearance (ml/min). Cessation of rifampin and isoniazid decreased warfarin fractional clearance from 15.2 to 4.2 ml/min, requiring a 50% reduction in warfarin dose to maintain the same prothrombin time.
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