Routine urinary detection of antihypertensive drugs for systematic evaluation of adherence to treatment in hypertensive patients

BACKGROUND:Nonadherence to antihypertensive therapy is an important cause of poor blood pressure control. However, to date, few effective and accurate tools exist to routinely evaluate drug nonadherence. METHODS:In this observational study, performed under conditions of routine clinical practice, we included 174 patients (aged 67 ± 11 years) with treated essential hypertension who attended the outpatient hypertension clinic of a university hospital. Adherence to antihypertensive treatment was measured by using ultraperformance liquid chromatography–tandem mass spectrometry in spot urine at the time of clinical appointment and blood pressure measurement. Patients were also asked to report their adherence using a validated questionnaire (four-item Morisky Medication Adherence Scale). RESULTS:The prevalence of directly measured nonadherence by urine drug detection was approximately 10%. Compared with adherent patients, those who did not adhere to their treatment (n = 15) had a higher number of antihypertensive pills and drugs (P = 0.02), cotreatment with cardiovascular drugs (P