Physicians' prescribing of anti-hypertensive combinations in a tertiary care setting in southwestern Nigeria.

PURPOSE To evaluate physicians' prescribing of anti-hypertensive drug combinations in a tertiary care setting in southwestern Nigeria, determine the degree of usage of Angiotensin Converting Enzyme (ACE) inhibitor-based combinations and identify specific points of intervention to improve outcomes of anti-hypertensive combination therapy. METHODS A cross-sectional retrospective drug use review was conducted between June 1st and August 31st 2002 using randomly selected 200 case notes of patients attending the Hypertension Clinic at a 900-bed tertiary care facility in southwestern Nigeria. 11 case notes were not used due to incompleteness. RESULTS 73% (138) of the patients were on anti-hypertensive drug combinations, comprising 71.7% (99), 24.4% (34) and 3.6% (5) on combinations of two, three and four drugs respectively. Overall, Thiazide diuretic consisting mainly of fixed dose combination of Amiloride and Hydorchlorothiazide (Moduretic(r)) was the most frequently prescribed drug class in anti-hypertensive combination therapy (83.3%). ACE inhibitor, Lisinopril (Zestril(r)), was prescribed in combination with Moduretic(r), Calcium channel blocker and beta-blocker in 6.5%, 8.5% and 0.7% respectively. Blood pressure control was adequate in only 29% (40) of patients, though adherence with therapy was documented as adequate in 77.5% (107). Type-2 diabetes mellitus (32.7%) and osteoarthritis (21.8%) were the most frequent co-morbidities. Potentially harmful drug-drug interactions in the study sample were identified in 17.5% (46) of patients. Physician documentation of adverse drug reactions among patients was done in only 10.9% of cases. There appear to be no institutionalised system in place to monitor, detect and document adverse drug reactions among patients on anti-hypertensive drug therapy. CONCLUSION Physicians' prescribing of anti-hypertensive drug combinations in a tertiary care setting in southwestern Nigeria is considerable. However, this practice does not appear to have positively impacted on blood pressure control among hypertensive patients nor being modulated by an Institutionalised standard guide.