Combined antihypertensive therapy has obvious advantages over single drug therapy. Hypertension guidelines fully affirm the efficacy of dual combination in initial antihypertensive therapy. Recent studies have also pointed out that the quadruple combination of very low-dose antihypertensive drugs is superior to single drugs. However, whether low-dose quadruple therapy is better than dual combination is unknown.

To evaluate and compare the efficacy and safety of half-dose quadruple therapy vs standard-dose dual therapy in the initial treatment of hypertensive patients with systolic/diastolic blood pressure 140-179/90-109 mm Hg.

A randomized double-blind crossover clinical trial will be conducted to compare the efficacy and safety of low-dose quadruple antihypertensives (irbesartan 75 mg + metoprolol 23.75 mg + amlodipine 2.5 mg + indapamide 1.25 mg) with standard-dose dual antihypertensives (irbesartan 150 mg + amlodipine 5 mg) in the initial treatment of patients with mild to moderate hypertension (140-179/90-109 mm Hg). Ninety patients are required and will be recruited and randomly assigned in a 1:1 ratio to 2 crossover groups. Two groups will receive a different combination therapy for 4 weeks, then switch to the other combination therapy for 4 weeks, with a 2-week wash-out. The patients will be followed up for 4 weeks to compare the antihypertensive effects and related adverse effects of the 2 antihypertensive combination treatments.

We present the rationale for the design of the QUADUAL trial. The trial started in July 2022 and is expected to be completed by August 2023. The study aims to evaluate if an initial treatment regimen of quadruple combination of half-dose blood pressure medications will result in greater reduction in blood pressure and fewer side effects compared to standard dose dual therapy.

www.clinicaltrials.gov (NCT05377203).