The effect of converting from pravastatin to simvastatin on the pharmacodynamics of warfarin

Forty-six adult patients maintained on warfarin therapy were converted from pravastatin to simvastatin. Mean international normalized ratio (INR) sign ificantly increased from 2.42 to 2.74, p = 0.002. Although warfarin doses w ere reduced in 7 patients and increased in 4 patients following the post-co nversion INR measurements, the pre- and postconversion median weekly warfar in dose of all 46 patients did not differ significantly. The number of pati ents with an INR > 3.0 increased significantly from 6 to 16 following the c onversion. There was no report of unusual episodes of bleeding. The results indicate that antihyperlipidemic therapy can be changed safely from pravas tatin to simvastatin in patients who are taking warfarin concomitantly;Addi tional anticoagulation monitoring is not necessary in institutions where pa tients are followed in formal anticoagulation clinics. Journal of Clinical Pharmacology; 1999;39:86-90 (C) 1999 the American College of Clinical Pharm acology.