Background: Metformin plays an important role in diabetes treatment. Studies have shown that the combined use of oral hypoglycemic medications is more effective than metformin monotherapy. In this double-blind, randomized, placebo-controlled, multicenter trial, we evaluated whether Jinlida, a Chinese herbal medicine, enhances the glycemic control of metformin in type 2 diabetes patients whose HbA1c was ineffectively controlled with metformin alone.

Methods: A total of 186 diabetes patients were enrolled in this double-Blind, randomized, placebo-controlled, multicenter trial. Subjects were randomly allocated to receive either Jinlida (9 g) or the placebo TID for 12 consecutive weeks. All subjects in both groups also continuously received their metformin without any dose change. During this 12-week period, the HbA1c, FPG, 2h PG, body weight, BMI were assessed. HOMA insulin resistance (HOMA-IR) and β-cell function (HOMA- β) were also evaluated.

Results: At week 12, compared to the HbA1c level from week 0, the level of the Jinlida group was reduced by 0.92 ± 1.09% and that of the placebo group was reduced by 0.53 ± 0.94%. The 95% CI was 0.69 - 1.14 for the Jinlida group vs. 0.34 - 0.72 for the placebo group. There was a very significant HbA1c reduction between the two groups after 12 weeks (p < 0.01). Both FG and 2h PG levels of the Jinlida group and placebo group were reduced from week 0. There were a very significant FG and 2h PG level reductions between the two groups after 12 weeks (both p < 0.01). The Jinlida group also showed improved β-cell function with a HOMA-β increase (p < 0.05). No statistical significance was observed in the body weight and BMI changes. No serious adverse events were reported.

Conclusion: Jinlida significantly enhanced the hypoglycemic action of metformin when the drug was used alone. This Chinese herbal medicine may have a clinical value as an add-on medication to metformin monotherapy.

Trial Registration: Chinese Clinical Trial Register ChiCTR-TRC-13003159