Prevalence and outcomes of drug interactions in hypertensive patients at Kenyatta National Hospital.

Abstract

Background: Drug interactions are a cause for concern as they increase morbidity and mortality. Few studies have been done to identify common drug interactions specifically in hypertensive patients, in whom the concurrent use of multiple drugs to manage their hypertension and attendant comorbidities is the norm. This makes hypertensive patients particularly susceptible to drug interactions. It is important to look for drug interactions in hypertensive patients so as to avoid outcomes that may alter management unfavourably in these patients. This study therefore sought to examine drug interactions in hypertensive patients at Kenyatta National Hospital. Objective: To determine the prevalence and clinical outcomes of drug interactions in hypertensive patients at Kenyatta National Hospital. Methods: This was a cross-sectional study done in inpatient and outpatient units in Kenyatta National Hospital. A sample of 313 hypertensive patients above 18 years who were admitted to the medical wards or visited the medical outpatient clinic between May to July 2016 were enrolled into the study. Data on patient demographics, clinical characteristics, risk factors and medication histories were collected through interviews and extracted from medical records. Potential drug interactions were investigated using established online drug interaction checkers. Descriptive statistics and cross tabulation chi square test was done to describe the prevalence and outcomes of drug interactions, and to determine the risk factors associated with drug interactions and comorbidities. Results: It was found that 92.7% of prescriptions had at least one potential drug interaction. A total of 1086 DDIs were found, translating to approximately 3.5 drug-drug interactions per patient. Majority (79.2%) of the identified DDIs were categorized as being moderate interactions; major and minor interactions were 4.1% and 16.8%, respectively. The most frequent major interaction noted in this study was enalapril + spironolactone (hyperkalaemia). The most frequently occurring interacting drug pair was enalapril + furosemide (4.4%) and this was followed by omeprazole + furosemide (3.5%). It was found that 91% of the patients had at least one comorbidity. Diabetes mellitus was the predominant comorbidity with a frequency of 40.6% followed by Chronic Kidney Disease (34.5%). A statistically significant relationship was found between the number of prescribed drugs and patient status (p<0.001), duration of hospitalization (p<0.001) and number of comorbidities (p= 0.006). Conclusions: This study detected a high prevalence of potential drug interactions. Some of the other major potential outcomes of these interactions included bronchospasms, rhabdomyolysis, decreased antihypertensive effects and hypersensitivity reactions. These findings will aid in safer prescribing by revealing the more important and frequently occurring potential drug interactions, thereby aiding to avoid adverse drug events that are detrimental to the patient