Drug Therapy Problems Among Adult Patients With Thromboembolic Disorders at Kenyatta National Hospital

Abstract

Background: Drug therapy problems are undesirable events experienced by patients that involve, or are suspected to involve medication being utilized. Studies assessing drug therapy problems among patients with thromboembolic disorders are scanty in resource limited areas. Objective: To describe the pattern of drug therapy problems among adult patients with thromboembolic disorders at Kenyatta National Hospital. Methodology: Convenient sampling was used to conduct a descriptive cross-sectional study that involved 113 adult patients with thromboembolic disorders at Kenyatta National Hospital outpatient clinics. Clinical data such as medications used, comorbidities and indication for drug therapy was abstracted from the files and recorded in the questionnaire while sociodemographic details were obtained through face-to-face interviews. Drug therapy problems were identified by asking patients questions to determine their adherence and how they were doing to gauge if they needed additional therapy, and checking their medications’ use. Outcomes of drug therapy problems were assessed through establishment of anticoagulation profiles and adverse effects such as bleeding. Data Management and Statistical Analysis: Raw data was entered into a pre-generated Microsoft Excel version 2023 spreadsheet and exported to STATA v.13 for statistical analysis. Descriptive statistics was done using both STATA v.13 and Ms. Excel. Bivariate analysis was conducted using Pearson’s Chi test and Fischer Exact test. Predictor variables with statistically significant associations were further subjected to multivariate analysis and backwards stepwise elimination model was used to identify independent predictors of drug therapy problems. Results: Majority of the participants were female (70.8%) and the median age was 51 years [IQR= 39, 62]. The main indication for antithrombotic therapy was for management of cardioembolic events (58.4%). The overall prevalence of drug therapy problems was 63.7% with the most common drug therapy problems being nonadherence (46.9%), additional therapy needed (35.4%), drug interactions (31%) and adverse drug reactions (14.4%). The major outcomes of these drug therapy problems were poor anticoagulation (28.4%) and bleeding events (3.5%). The independent predictors of drug therapy problems were the use of proton pump inhibitors [aOR=7.155, 95% CI: (0.861, 59.444), p=0.029] and diuretics [aOR=2.689, 95% CI: (1.193, 6.059), p=0.017], meaning that patients on these drugs had 7.155 times and 2.689 times chance of developing drug therapy

problems compared to those not on these drugs. Independent predictors of occurrence of drug interactions included polypharmacy [aOR=8.413, 95% CI: (2.761,25.641), p=0.001] the use of proton pump inhibitors [aOR=10.116, 95% CI: (1.647, 62.103) p=0.012] and vitamin supplements [aOR=41.322, 95% CI: (3.817, 447.288), p=0.002]. The use of clopidogrel was a significant independent predictor for nonadherence, though this association was lost on logistic regression [aOR=7.531, 95% CI: (0.876, 64.751), p=0.066]. The use of calcium channel blockers was an independent predictor of occurrence of adverse drug reactions [aOR=3.708, 95% CI: (0.968, 14.205), p=0.046]. Conclusion: The prevalence of drug therapy problems among patients with thromboembolic disorders was mainly due to nonadherence. The high prevalence of drug therapy problems among patients on diuretics and proton pump inhibitors suggests that anticoagulation management should be intensified in patients receiving these medications. Despite nonadherence being the most prevalent drug therapy identified, only one medication related factor was identified as a significant independent predictor. Further qualitative research should be done to identify non-clinical and non-medical factors that influence non-adherence in patients with thromboembolic disorders.