Because of substantial interpatient differences in sensitivity to warfarin, numerous variables that can alter the response to therapy with time, and the potential risk for major hemorrhage, a systematic approach to therapeutic drug monitoring must be carried out for every patient with anticoagulant therapy. The purpose was to identify most frequent existent possible warfarin interactions in the hospital drug prescribing, analyze the effects of interactions on the warfarin dose for cardiological elderly patients. In this study patients (age >65) with indications for warfarin therapy from cardiological department of the hospital were included at the time from May 2009 to September 2009. A total of 100 patients (60 male, 40 female) met the study inclusion criteria. The mean age was 69 ± 3 years. Concomitant other drugs were analyzed which are known either to prolong the prothrombin time or international normalized ratio (INR) or interact with warfarin such as amiodarone (25%), statins (13%), anti-inflammatory drugs (aspirin (4%)), proton pump inhibitor (omeprazole (4%)) In this study we found inverse correlation between starting dose of warfarin and maintenance dose of amiodarone (r2 = 0.94, p < 0.005). When we calculated the dose of anticoagulant for these patients, it seemed to be decreased for 32% mean maximum in the warfarin dose being required by the elderly population with concomitant warfarin and amiodarone therapy (200mg/d). The clinical caveats in the elderly include reduced starting doses, elimination of unnecessary medications and anticipating and monitoring for drug interactions, especially when prescribing warfarin and amiodarone.
Loading....