Efficacy and Safety of a Quadruple Ultra-low-dose Treatment for Hypertension (QUARTET USA): Rationale and Design for a Randomized Controlled Trial

Background: Over half of patients with elevated blood pressure require multi-drug treatment to achieve blood pressure control. However, multi-drug treatment may lead to lower adherence and more adverse drug effects compared with monotherapy.

Objective: The Quadruple Ultra-low-dose Treatment for Hypertension (QUARTET) USA trial was designed to evaluate whether initiating treatment with ultra-low-dose quadruple-combination therapy will lower office blood pressure more effectively, and with fewer side effects, compared with initiating standard dose monotherapy in treatment naive patients with SBP < 180 and DBP < 110 mm Hg and patients on monotherapy with SBP < 160 and DBP < 100 mm Hg.

Methods/design: QUARTET USA was a prospective, randomized, double-blind trial (ClinicalTrials.gov NCT03640312) conducted in federally qualified health centers in a large city in the US. Patients were randomly assigned (1:1) to either ultra-low-dose quadruple combination therapy or standard dose monotherapy. The primary outcome was mean change from baseline in office systolic blood pressure at 12-weeks, adjusted for baseline values. Secondary outcomes included measures of blood pressure change and variability, medication adherence, and health related quality of life. Safety outcomes included occurrence of serious adverse events, relevant adverse drug effects, and electrolyte abnormalities. A process evaluation aimed to understand provider experiences of implementation and participant experiences around side effects, adherence, and trust with clinical care.

Discussion: QUARTET USA was designed to evaluate whether a novel approach to blood pressure control would lower office blood pressure more effectively, and with fewer side effects, compared with standard dose monotherapy. QUARTET USA was conducted within a network of federally qualified healthcare centers with the aim of generating information on the safety and efficacy of ultra-low-dose quadruple-combination therapy in diverse groups that experience a high burden of hypertension.