Nonadherence was revealed through measurements of serum concentrations of antihypertensive drugs in one-third of patients with resistant hypertension previously evaluated as adherent. 11 Sep, 2022 | 22:35h | UTC Nonadherence by Serum Drug Analyses in Resistant Hypertension: 7‐Year Follow‐Up of Patients Considered Adherent by Directly Observed Therapy – Journal of the American Heart Association