The patients routinely visit the clinic for assessment, which includes point of care INR testing, assessment of dietary vitamin K intake, pill count based assessment for adherence, refill of warfarin into pill boxes and monitoring of adverse events due to warfarin such as this website bleeding. Warfarin doses are adjusted based on these

factors using a comprehensive protocol based on the American College of Chest Physician Guidelines (2008) [21]. Information on the patient encounter is recorded on a standardized form, which is completed at every visit. The frequency of patient visits is dependent upon the consistency of their INR within the therapeutic range and accessibility to the clinic [18]. The study included all patients on concurrent warfarin and rifampicin therapy enrolled in the PD-0332991 nmr clinic from May 2009 to June 2011 and on follow-up at the anticoagulation clinic for a minimum of

2 months. Patients on antiretroviral therapy were excluded due to the potential for additional drug interactions, which would limit the ability to focus on the impact of rifampicin. Data was collected from the patient charts that contained their initial encounter form and routine assessment forms. Patients were assessed for time to therapeutic INR, average weekly warfarin dose on attaining therapeutic INR, time in therapeutic range (TTR) and level of adherence. Institutional Review Board CAL-101 solubility dmso (IRB) approval was obtained from the local institutional review and ethics committee at MTRH/Moi University and the Indiana University-Purdue University Indianapolis (IUPUI) IRB. In this study, time to therapeutic INR is defined as the time taken to achieve two consecutive therapeutic INRs. The average weekly warfarin doses on attaining therapeutic INR were calculated with similar considerations. Time in therapeutic range (TTR) is calculated using the linear interpolation method described

Fossariinae by Rosendaal et al. [22] and weighted by the duration of follow-up of each patient. The model assumes that the INR changes linearly between measurements and estimates the percentage of time spent in the therapeutic range. Adherence to therapy is generally defined as the extent to which patients take medications as prescribed by their health care providers. It may also include details on the patient’s dose taking tendencies [23]. In this case series, our definition encompasses both and therefore refers to adherence with the prescribed warfarin regimen as indicated by the healthcare provider. In order to improve outcomes from the, often complicated, warfarin dosing regimens, all of the warfarin is dispensed in pill boxes with adherence assessed via pill box based pill counts at each clinic visit.