Potential drug-drug interactions among patients with type 2 diabetes and hypertension in Kisii Teaching and Referral Hospital, Kenya

Abstract

Introduction Hypertension in diabetics represents an important health problem as the combination of these ailments is common, and can carry significant morbidity and mortality rates. The prevalence of hypertension in diabetic people is probably 1.5–2 times higher than in the general population. Patients with Type 2 diabetes and hypertension routinely receive a combination of several drugs to treat both of these chronic conditions, and as such, the possibility of drug interactions is high. There are no local studies on prevalence of potential drug-drug interactions among patients receiving both hypoglycemic and antihypertensives and thus the need to carry out the study. Objective To assess the selection, combination and possible drug-drug interactions of pharmacological agents used in the management of outpatients with both hypertension and diabetes at Kisii Teaching and Referral Hospital. Methods A hospital-based cross-sectional study design was used. The study comprised two quantitative cross-sectional studies were conducted. In the first study, medical records data for 168 patients from outpatient department were sampled using modified systematic random sampling technique. All prescriptions of drugs were checked for compliance with treatment guidelines and for any drug-drug interaction using Medscape Interaction Checker. A survey on awareness of drug–drug interaction among prescribers and dispensers was carried out on a sample size of 30, by questionnaire-guided interviews. Descriptive statistics was used to summarize variables. Statistical analyses were done using the statistical software Epi info 7 and Stata version 10. Results Swelling of limbs (7.8%) was the common co-morbidity. About 76% of the prescriptions conformed to International Diabetes Federation and World Health Organization hypertension treatment guidelines. Using Medscape Interaction Checker, 96% prescriptions had least one drug-drug interaction. Overall 672 drug-drug interactions were detected, with an average of 4

interactions per prescription. Thirty four (5%) of the potential interactions were classified as major interactions, while most of the potential drug-drug interactions (334, 50%) were moderate. The most common major interaction was losartan and enalapril followed by enalapril and pregabalin. The common moderate drug-drug interactions were insulin and enalapril, metformin and ciprofloxacin, and glibenclamide and enalapril. Fifty four percent of the drug-drug interactions were pharmacodynamic, while the rest (31%) were pharmacokinetic in nature. Most of the potential major (13 of 26) and moderate (97 of 333) interactions involved a combination of antihypertensive and other drugs. Polypharmacy, use of sulfonylurea, use of metforminand patient weight were positively associated with the number of drug-drug interactions. Polypharmacy had the greatest influence on drug-drug interactions accounting 31.3%. average number of drus per prescription was 5. There were 43% of the respondents that could cite the various guidelines that are used for management of diabetes and hypertension. Most of the respondents (67%) could not identify specific interactions when presented with commonly prescribed drug combinations involving hypoglycemics and antihypertensives. Conclusion The prevalence of potential drug-drug interactions was high. There is a knowledge gap among health workers regarding drug-drug interactions. All prescriptions should be analyzed for drug-drug interactions and this should be done by prescribers and dispensers