Introduction: Selection of antihypertensive therapy hinges on an appropriate combination of efficacy, tolerability and compatibility with co-morbidities. Within a given class of antihypertensives, the choice of agent is often driven by cost, with the cheapest appropriate agent being chosen. Amongst the angiotensin receptor blockers (ARBs), this choice will often be losartan, as it is available in generic form. However, as the blood pressure lowering efficacy of losartan is modest, some patients will require an alternative ARB. In the UK this choice is often candesartan, although the agent with greatest BP lowering efficacy is olmesartan. The objective of this study was to use a cost-benefit model to compare the costs associated with target achievement using each of these two agents, in order to guide optimum use of prescribing budgets.
Method: A probabilistic cost-benefit model was constructed for a cohort of patients with moderate hypertension, based on a standardised titration and maintenance algorithm using either olmesartan or candesartan, combined with thiazide and calcium channel blocker where required. Direct treatment costs were recorded, along with the proportion of patients achieving pre-defined treatment targets at each treatment level. Results were expressed as mean treatment cost per patient reaching target.
Results: Based on the current QoF target of 150 mmHg systolic, 94.3% of patients on the olmesartan-based regimen reached target of 150 mmHg, compared with 89.0% of those on the candesartan-based regimen. 86% of olmesartan patients reached target on <3 drugs, compared with 74% of candesartan patients. The mean 12-month cost per patient reaching target was £171.36 for olmesartan versus £189.91 for candesartan. Ongoing annual maintenance costs for patients at target were £169.97 and £182.64, respectively. Similar results were obtained when considering alternative treatment targets
Limitations: The study only compared two ARBs - candesartan and olmesartan and the results relate to prescribing costs only and do not include other healthcare costs. Additionally, the chosen outcome was blood pressure target achievement, rather than clinical endpoints. Given the stated objectives of the model, we do not believe these issues will have introduced bias in the direction of either comparator
Conclusion: Although olmesartan has an apparently higher acquisition cost than candesartan, its superior BP lowering efficacy means that the overall cost per patient treated to target is actually lower. This result could have significant implications for making savings within primary care prescribing budgets in the UK.