Identification and Characterization of Potential Drug Interactions in Hypertensive Patients in a Kenyan Tertiary Hospital

Background: Hypertensive patients are particularly at risk of drug-drug interactions resulting from the concomitant use of multiple drugs to control their blood pressure. The presence of comorbidities and advancing age are also likely to contribute to the use of many drugs, further increasing this risk. Drug related problems such as drug interactions in the management of hypertension increase morbidity and mortality but there are limited published data to characterize them especially among the African population. Objective: To identify and characterize potential drug interactions among adult hypertensive patients attending Kenyatta National Hospital. Methods: This was a descriptive cross-sectional study done among 313 adult patients between May to July 2016 at Kenyatta National Hospital. Ethical approval was sought from the institutional review board. Data on patient demographics, clinical characteristics and current prescriptions were extracted from patient records into predesigned data collection forms. Potential drug interactions were identified using an online Drug Interactions Checker. Results: There was female predominance at 60.7% and the mean age of the study population was 55.2 years (SD 15.9).  The mean number of drugs per prescription was 5.93 (SD 2.24). The prevalence of potential drug interactions was 92.7%. There was an average of 3.5 drug interactions per prescription. Majority (79.2%) of the potential drug interactions were categorized as moderate while major and minor interactions accounted for 4.1% and 16.8%, respectively. The most prevalent interacting drug pair was enalapril and furosemide (15.3 %). The most frequent major interaction found was between enalapril and spironolactone, which is associated with hyperkalaemia. Conclusions: There was a high prevalence of potential drug interactions. Prescribers should be encouraged to be vigilant during the management of hypertensive patients to avoid overt drug interactions which may compromise treatment outcomes and increase the health care costs.