AT1 receptor blockers--cost-effectiveness within the South African context

Hypertension is a leading chronic disease in South Africa, Significant mortality results from this condition and from stroke and ischaemic heart disease in which hypertension plays a major role. The objective of this study was to evaluate the evidence for the clinically effective and cost-effective treatment of hypertension, given that the clinician has decided to administer an AT1 receptor blocker.

A cost-effectiveness analysis was undertaken from the perspective of the funder of health care in the private sector. A predetermined protocol defined the study scope, the comparators (candesartan, losartan, valsartan and irbesartan) and the inclusion criteria for peer-reviewed data. Data for the clinical efficacy of the comparators, measured as the reduction (mmHg) in sitting diastolic blood pressure (SDBP) achieved, were extracted, statistically assessed and reported. The combinability of the data from different clinical trials was confirmed using analyses of variance. A pharmacoeconomic model was developed by combining these clinical results with South African retail prices and testing the results at a 95% confidence level.

Significant difference in clinical effectiveness was found among the comparators, with the following mean reductions in SDBP observed: candesartan 10.57, irbesartan 9.07, losartan 8.89 and valsartan 7.11 mmHg. Candesartan was found to be significantly more effective than losartan. Valsartan was found to be less effective than the other 3 comparators. No significant difference was found between irbesartan and either candesartan or losartan. The reduction in SDBP per R100 spent indicated that candesartan was more cost-effective than the other comparators, among which there were no significant differences. Incremental savings of R5.0 million annually could be achieved by the funders of private health care for every 100,000 successfully treated patients using candesartan.

Significant differences exist in both the clinical and cost-effectiveness measures used in this study for the comparators. The findings from the analysis will be valuable in decision-making processes for both the funders and providers of health care. This analysis can be enhanced further by the inclusion of additional clinical benefits and long-term health outcomes when the relevant data become available.