Clinically Significant Potential Drug-drug Interactions Among Adult Diabetic Hypertensive Outpatients at Kenyatta National Hospital

Abstract

Background: Type 2 diabetes mellitus (DM) and hypertension are common comorbidities in the developing and developed world. Management of these patients requires combination pharmacotherapies which may lead to polypharmacy and subsequently drug-drug interactions. Such interactions may produce undesirable clinical outcomes. Broad objective: To characterize the clinically potential drug-drug interactions and their significance among adult diabetic hypertensive outpatients at Kenyatta National Hospital. Methods: This was a tertiary hospital based cross-sectional study done among 104 adult patients from 1st May 2019 to 31st August 2019 at Kenyatta National Hospital. Ethical approval was obtained from the institutional review board under reference number KNH-ERC/A/192. Data on patient demographics, clinical characteristics current prescriptions and strategies for prevention of potential drug-drug interactions were extracted from patient records into predesigned data collection forms. Potential drug interactions were identified using the Micromedex drug interaction checker®. Data was exported to STATA software version 13 for analysis. The level of significance was set at 0.05 Results: There were more females (70.2%) in the study. The mean age of the participants was 61.6 years (SD±10.8). The prevalence of potential drug interactions was high at 57.7%. The average number of interactions was one interacting pair per patient with majority (81.0%) of the prescriptions having moderate drug-drug interactions which were significantly associated with the advanced stage of hypertension (COR=2.63; 95% CI 1.5-4.68; p=0.002), number of drugs prescribed (COR=2.12; 95% CI 1.15-3.92; p=0.020), use of nifedipine(COR=6.42; 95% CI 1.31-31.57; p=0.008) and losartan(COR=4.60; 95% CI 0.99-21.36; p=0.005). The most common potential clinical outcome was hyperkalemic lactic acidosis (14.4%) associated with co-prescribing of enalapril and metformin (14.4%). Potential drug interactions were minimized through regular blood sugar check (100%) and blood pressure monitoring (98.1%). However, there was minimal monitoring of HbA1c (30.8%) as well as serum urea and electrolytes (17.3%). Conclusion: The prevalence of potential drug-drug interactions was high. Multi-drug therapy, advanced stage of hypertension and use of nifedipine increased the risk of potential drug-drug interactions which were mitigated through patients monitoring of their disease. Recommendations: Patients with comorbid diabetes and hypertension would benefit from cautious prescription and use of drugs which are less likely to cause drug-drug interactions as well as close monitoring of blood sugars, blood pressures, HbA1Cs, urea and electrolytes. Future large cohort studies may be required to assess the impact of patients monitoring and the actual drug-drug interactions.