A comparison between persistence to therapy in ALLHAT and in everyday clinical practice: a generalizability issue

Persistence to therapy was very high in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) and was similar between treatment arms. Most patients were already on antihypertensive therapy before the trial began. Clinically, the results from this trial are more likely to be applied when antihypertensive therapy is initiated.

To assess whether the conclusions drawn from ALLHAT could be applied to the initiation of antihypertensive therapy.

A MEDLINE literature search was performed using the key words 'persistence', 'persistence to therapy', 'compliance' and 'adherence', and these were each linked with 'hypertension'. Studies from pharmaceutical databases were selected when they reported persistence to any antihypertensive therapy at one year according to which initial drug class (calcium channel blockers, angiotensin-converting enzyme inhibitors and thiazides) was initially prescribed. From the reported persistence rates, the number of patients was determined in whom treatment of hypertension results in a waste of health resources when each initial drug class was prescribed.

Persistence to antihypertensive therapy at one year reported in the pharmaceutical databases varies from 5% to 75%. It was lower when the initial drug that was prescribed was a diuretic versus an angiotensin-converting enzyme inhibitor or a calcium channel blocker. The number of patients in whom treatment of hypertension resulted in a waste of resource was also higher when a diuretic was initially prescribed.

Persistence to antihypertensive therapy is low for all the agents initiated and the lowest with diuretics. This should be considered as a word of caution when the ALLHAT conclusions are applied to the clinical setting.