ObjectiveSingle-pill amlodipine besylate (AML) plus losartan (LOS) has been used to treat inadequately controlled hypertension after antihypertensive monotherapy; however, relevant data in China are limited. This study aimed to compare the efficacy and safety of single-pill AML/LOS and LOS alone in Chinese patients with inadequately controlled hypertension after LOS treatment.MethodsIn this multicenter, double-blind, randomized, controlled phase III clinical trial, patients with inadequately controlled hypertension after 4 weeks of LOS treatment were randomized to receive daily single-pill AML/LOS (5/100 mg, AML/LOS group,N= 154) or LOS (100 mg, LOS group,N= 153) tablets for 8 weeks. At weeks 4 and 8 of treatment, sitting diastolic and systolic blood pressure (sitDBP and sitSBP, respectively) and the BP target achievement rate were assessed.ResultsAt week 8, the sitDBP change from baseline was greater in the AML/LOS group than in the LOS group (−8.84 ± 6.86 vs. −2.65 ± 7.62 mmHg,P< 0.001). In addition, the AML/LOS group also showed greater sitDBP change from baseline to week 4 (−8.77 ± 6.60 vs. −2.99 ± 7.05 mmHg) and sitSBP change from baseline to week 4 (−12.54 ± 11.65 vs. −2.36 ± 10.33 mmHg) and 8 (−13.93 ± 10.90 vs. −2.38 ± 12.71 mmHg) (allP< 0.001). Moreover, the BP target achievement rates at weeks 4 (57.1% vs. 25.3%,P< 0.001) and 8 (58.4% vs. 28.1%,P< 0.001) were higher in the AML/LOS group than those in the LOS group. Both treatments were safe and tolerable.ConclusionSingle-pill AML/LOS is superior to LOS monotherapy for controlling BP and is safe and well tolerated in Chinese patients with inadequately controlled hypertension after LOS treatment.