Background and objective: Budgetary pressures within health care systems have led many health care providers to consider the switching of patients on long term anti hypertensive medication to agents with the lowest acquisition price. The long term success of this strategy hinges on price differentials remaining stable, an assumption that may not be valid in drug classes where patent expiry times vary. The treatment of hypertension using angiotensin receptor blockers (ARBs) represents just such a case. The present study, therefore, modelled the 5-year cost consequences of treatment based on losartan, candesartan, valsartan and irbesartan, based on expected patent expiry dates.
Methods: A Markov model was constructed, applying dose-specific blood-pressure lowering and costs to a cohort of uncontrolled mild-moderate hypertensive patients and assessing the anticipated cost of treatment over a 5 year period. A probabilistic approach was adopted to account for between-patient and between-treatment differences.
Results: For both undiscounted and discounted models, a losartan-based regimen represents the least costly option of the four agents tested. Median (IQR) discounted expenditure per patient for each agent was: losartan: pound 506 ( pound 441- pound 650), candesartan: pound 610 ( pound 542- pound 766), valsartan: pound 809 ( pound 796- pound 1078), irbesartan pound 696 ( pound 694- pound 934).
Conclusion: Switching hypertensive patients taking ARBs to the agent with the lowest current acquisition cost may yield only transient budgetary savings. Once patent expiry is taken into account, this model suggests that maintaining or switching patients to losartan would yield considerably greater savings over 5 years.