Safety and Efficacy of Low Dose (7.5 mg) as Compared to Standard Dose (15 mg) Pioglitazone in Type 2 Diabetes and Metabolic Syndrome: A Systematic Review and Meta-analysis

INTRODUCTION: Weight gain and fluid retention with pioglitazone appear dose-dependent, and South/East Asian populations may retain glycemic benefit at lower doses. This systematic review and meta-analysis compared low-dose pioglitazone (LDP, 7.5 mg/day) with standard-dose pioglitazone (15 mg/day) - and secondarily with 30 mg/day and placebo - in type-2 diabetes (T2D) and metabolic syndrome (MetS). METHODS: PubMed, Embase, and Cochrane Library were searched for studies of T2D and/or MetS patients receiving pioglitazone 7.5 mg/day versus 15/30 mg/day or placebo. Primary outcomes were change in body weight and body mass index (BMI); secondary outcomes were edema, glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), lipids, and liver enzymes. Random-effects (inverse-variance) models were used; heterogeneity was assessed with I2 and prediction intervals (PI). Risk of bias was assessed using RoB2 and ROB In Non-randomized Studies-of Interventions. RESULTS: Twelve studies were included. Versus 15 mg/day, 7.5 mg/day produced significantly less weight gain (mean difference [MD]: -1.61 kg [95% confidence interval: -2.13, -1.08]; P < 0.001; I2 = 56%; PI: -2.66, -0.55) and a smaller BMI rise (MD - 0.47 kg/m2 [-0.68, -0.26]; P < 0.001; I2 = 18%; PI: -0.78, -0.16), both robust on PI analysis. HbA1c was comparable at 3 months (MD 0.08% [-0.18, 0.34]; P = 0.53) and 6 months (MD 0.18% [-0.05, 0.42]; P = 0.13). Edema was lower with 7.5 mg/day but only borderline (odds ratios 0.19 [0.04, 0.99]; P = 0.05; I2 = 71%) and non-significant on PI analysis. FPG was similar at 3 months but modestly higher with 7.5 mg/day at 6 months (MD 7.71 mg/dl [1.64, 13.78]; P = 0.01), a difference not retained on PI analysis. Low-density lipoprotein-cholesterol and triglycerides were comparable; high-density lipoprotein-cholesterol (HDL-C) was marginally lower with 7.5 mg/day (MD: -2.11 mg/dl [-2.47, -1.75]). Weight and BMI advantages were also seen versus 30 mg/day, with comparable HbA1c. No formal non-inferiority margin was prespecified. CONCLUSION: LDP (7.5 mg/day) offers HbA1c control comparable to 15 mg/day with less weight and BMI gain, supporting it as a candidate minimum effective dose. A modest 6-month FPG difference, slightly lower HDL-C, and predominantly ≤6-month follow-up warrant confirmation in longer trials.