Aims: This study assessed the efficacy of add-on pioglitazone vs. placebo in patients with type 2 diabetes uncontrolled by metformin and a sulphonylurea or a glinide.
Methods: This multicentre, double-blind, parallel-group study randomized 299 patients with type 2 diabetes to receive 30 mg/day pioglitazone or placebo for 3 months. After this time, patients continued with pioglitazone, either 30 mg [if glycated haemoglobin A1c (HbA(1c)) <or=6.5%] or titrated up to 45 mg (if HbA(1c) >6.5%), or placebo for a further 4 months. The primary efficacy end-point was improvement in HbA(1c) (per cent change). Secondary end-points included changes in fasting plasma glucose (FPG), insulin, C-peptide, proinsulin and lipids. The proinsulin/insulin ratio and homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of beta-cell function (HOMA-B) were calculated.
Results: Pioglitazone add-on therapy to failing metformin and sulphonylurea or glinide combination therapy showed statistically more significant glycaemic control than placebo addition. The between-group difference after 7 months of triple therapy was 1.18% in HbA(1c) and -2.56 mmol/l for FPG (p < 0.001). Almost half (44.4%) of the patients in the pioglitazone group who had a baseline HbA(1c) level of <8.5% achieved the HbA(1c) target of < 7.0% by final visit compared with 4.9% in the placebo group. When the baseline HbA(1c) level was >or= 8.5%, 13% achieved the HbA(1c) target of < 7.0% in the pioglitazone group and none in the placebo group. HOMA-IR, insulin, proinsulin and C-peptide decreased and HOMA-B increased in the pioglitazone group relative to the placebo group.
Conclusions: In patients who were not well controlled with dual combination therapy, the early addition of pioglitazone improved HbA(1c), FPG and surrogate measures of beta-cell function. Patients were more likely to reach target HbA(1c) levels (< 7.0%) with pioglitazone treatment if their baseline HbA(1c) levels were < 8.5%, highlighting the importance of early triple therapy.