Magnitude of pharmacological nonadherence in hypertensive patients taking antihypertensive medication from a community pharmacy in Spain

BACKGROUND: The most common factor associated with poor control of hypertension is treatment nonadherence to antihypertensive drug therapy. OBJECTIVE: To measure drug nonadherence and associated factors in pharmacologically treated hypertensive patients. METHODS: A prospective observational study was carried out from March 2007 to August 2009 at a community pharmacy in Spain. A pharmacist invited a convenience sample of hypertensive patients aged 50 years and older taking antihypertensive medication for at least 3 months prior to participate in the study. Drug nonadherence was analyzed by 3 separate methods: pill count, as the gold standard method, and Haynes-Sackett and Morisky-Green questionnaires. A descriptive analysis of drug nonadherence and variables associated with nonadherence was performed. Logistic regression models were used to determine the variables associated with nonadherence. RESULTS: Data were recorded from 419 patients. The drug nonadherence ratio varied depending on the method used: 62.8% by pill count, 3.1% by the Haynes-Sackett self-report test, and 36% according to the Morisky-Green test. In the multivariate model, the variable associated with a decrease in drug nonadherence was years of known hypertension (OR=0.962, 95% CI=0.937-0.988), and the variables associated with an increase in drug nonadherence were loose-pill combination therapy versus fixed-dose combination therapy or monotherapy (OR=4.099, 95% CI=2.494-6.757) and good perception of quality of life (OR=1.276, 95% CI=1.109-1.471). CONCLUSIONS: The magnitude of drug nonadherence varies depending on the method of measurement. The pill count method (reference method) revealed that 2 out of 3 patients with hypertension did not have good adherence. This study highlights the lack of antihypertensive drug adherence and the pharmacist’s ability to detect the as