Thiazide diuretics alone or combined with potassium-sparing diuretics to treat hypertension: a systematic review and network meta-analysis of randomized controlled trials

BACKGROUND: The magnitude of blood pressure (BP)-lowering effects and decrease of the adverse effects of thiazide diuretics provided by potassium-sparing diuretics remain uncertain. The aim of this study was to compare the BP-lowering efficacy and the incidence of adverse effects of high (T+) and low-dose (T-) thiazide diuretics, alone or combined with high (PS+) or low-dose (PS-) potassium-sparing diuretics in patients with primary hypertension. METHODS: A systematic literature search was performed in PubMed/MEDLINE, the Cochrane Central Register of Controlled Trials, Embase, Web of Science, Scopus and LILACS. Randomized double-blind placebo or active-controlled trials (RCT) with 3 weeks to 1 year of follow-up were included. Sample size, mean and standard deviation from baseline, follow-up and change from baseline values were extracted by two independent reviewers. Pairwise random effect models and Bayesian network meta-analysis models were used to compare the effects of treatments. The risk of bias in individual studies was assessed using the Rob 1.0 tool. The primary outcome was the mean difference in office SBP. Secondary outcomes were the mean difference in biochemical parameters and the incidence of nonmelanoma skin cancer. RESULTS: Two hundred and seventy-six double-blind RCTs involving 58 807 participants (mean age: 55 years; 45% women) were included. All treatment groups were more effective than placebo in lowering BP, with mean differences (MDs) of change from baseline ranging from –7.66 mmHg [95% credible interval (95% CrI), –8.53 to –6.79] for T- to –12.77 mmHg (95% CrI, –15.22 to –10.31) for T+PS-. T+ alone or combined with potassium-sparing was more effective in reducing BP than T-. The surface under the cumulative ranking curve (SUCRA) estimated ranking showed that the best effectiveness in lowering SBP was found for T+PS- (0.69), T+PS+ (0.65) and T+ (0.54). Compared with placebo, all treatments (except T-PS-) were associated with more potassium reduction and T+ compared with all other treatments and T- when compared with T-PS-. Compared with placebo, all active treatments (except T+PS+) showed higher elevations of uric acid. The increase of plasma glucose promoted by thiazides alone was reduced by potassium-sparing agents. CONCLUSION: Thiazides with potassium-sparing diuretics are associated with increased BP-lowering efficacy compared with thiazides alone while minimizing hypokalaemia and hyperglycaemia. These findings demonstrate that thiazide and potassium-sparing diuretic combination is preferable to thiazide alone in treating hypertension.