Frequency, types and factors associated with potentially harmful drug interactions in ambulatory elderly patients in Nigeria†

Abstract

Abstract Objective To determine the frequency, types and factors associated with potentially harmful drug interactions among ambulatory elderly (≥65 years) patients in Ibadan, Nigeria. Methods A 4-week cross-sectional study was conducted among 229 elderly patients who consented and were prescribed two or more medicines within a 4-week study period at a major 256-bed secondary care facility in Ibadan, Nigeria. Chi-square and risk ratio were used to identify the factors associated with the potentially harmful drug–drug interactions. Key findings Potentially harmful drug–drug interactions were identified in about two-thirds (65%, 149/229) of the patients. The risk of occurrence drug interactions was significantly higher among patients who had at least six prescribed medicines (relative risk: 7.8 (95% confidence interval, 6.9 to 9.5) (P < 0.001)), and a significant majority were also females (73.8%) (110) (P < 0.001). The most frequent interacting drug combination was angiotensin-converting enzyme inhibitors and amiloride + hydrochlorothiazide (34.7%). Conclusion Potentially harmful drug interactions that are significantly associated with high multiple prescribing are considerable among elderly patients in Nigeria.