Association of Plasma Warfarin level with Monitoring Parameters Among Patients Treated at Hematology Referral Clinic, Tikur Anbessa Specialized Hospital

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Addis Ababa University


Warfarin monitoring poses challenge to the treatment of thromboembolic disorders because out-of-range INRs which is encountered as a result of changes in numerous factors. The fluctuation of INR in some patients might be dangerous because of the narrow therapeutic index of warfarin. The objective of this study is to evaluate the association of plasma warfarin level with warfarin the clinical monitoring parameter, INR and related parameters. Institution based cross-sectional prospective study was conducted recruiting 57 eligible patients on warfarin treatment at hematology referral clinic of Tikur Anbessa Specialized Hospital. Clinical data was retrieved from patient cards and plasma warfarin level were determined using High Pressure Liquid Chromatography with Ultra Violet – Visible detector. The associations of plasma concentration with INR and weekly dose were low (rho = 0.375 at p = 0.006 and r = 0.283 at p = 0.04) respectively. There was also statistically significant difference in the mean plasma warfarin concentration of patients who took effect enhancing co-medication and those who took non-effect changing co-medication (p <0.001) as well between the mean plasma concentration of patients who took effect diminishing co-medication and those who took non-effect changing co-medications was also statistically significant (p = 0.005). In conclusion clinical monitoring parameters of warfarin have low association with plasma warfarin level. The low correlation indicates the importance of plasma warfarin concentration monitoring in some situations, especially when the ideal INR is difficult to achieve the target where by patient safety can be affected. Key Words: Warfarin, INR, Dose, Association, co-medications



Warfarin; INR; Dose; Association; co-medications