Background and objective: Repaglinide and metformin enhance insulin secretion and decrease hepatic gluconeogenesis, respectively, and are commonly coadministered as separate formulations to treat patients with type 2 diabetes mellitus. A single combination therapy tablet offers increased patient convenience and the subsequent potential for increased therapy compliance. The aim of this randomized, single-blind, three-period crossover study was to determine the bioequivalence of a fixed-dose combination (FDC) tablet of repaglinide/metformin 2 mg/500 mg versus repaglinide 2 mg and metformin 500 mg coadministered as separate formulations. Secondary objectives included a comparison of the dose proportionality of an FDC tablet of repaglinide/metformin 1 mg/500 mg and an FDC tablet of repaglinide/metformin 2 mg/500 mg, as well as the safety and tolerability of repaglinide and metformin in combination tablet therapy.
Methods: Healthy subjects (n = 93, age 18-45 years) were randomized to one of six possible treatment sequences (Williams design) of an FDC tablet of repaglinide/metformin 2 mg/500 mg, repaglinide 2 mg and metformin 500 mg coadministered as separate tablets and an FDC of repaglinide/metformin 1 mg/500 mg. Fifty-five subjects completed the study. Four primary pharmacokinetic endpoints (area under the plasma concentration-time curve [AUC] from time 0 hours to infinity; AUC from time 0 to 24 hours; AUC from time 0 hours to time t [the last time of measurable concentration after dosing]; and the maximum plasma concentration) were used to assess bioequivalence and dose proportionality. The safety and tolerability of repaglinide and metformin in combination tablet therapy were also evaluated.
Results: Both repaglinide and metformin in the combination tablet were determined to be bioequivalent to the individual tablets of repaglinide 2 mg and metformin 500 mg, as the limits of the 90% confidence interval of the mean treatment ratio for all pharmacokinetic parameters were contained within the pre-specified interval required for bioequivalence (0.8, 1.25). Additionally, an FDC tablet of repaglinide/metformin 2 mg/500 mg was determined to be dose proportional to an FDC of repaglinide/metformin 1 mg/500 mg for all analysed endpoints. No withdrawals as a result of adverse events occurred during this study. In addition, no clinically relevant abnormalities were found during physical examinations, in vital signs, ECG parameters or clinical laboratory parameters.
Conclusion: An FDC tablet of repaglinide/metformin 2 mg/500 mg was bioequivalent to individual tablets of repaglinide 2 mg and metformin 500 mg. Additionally, an FDC tablet of repaglinide/metformin 2 mg/500 mg was dose proportional to an FDC tablet of repaglinide/metformin 1 mg/500 mg. Finally, no unexpected safety concerns were noted with repaglinide/metformin combination tablet therapy. Our results suggest that FDC tablets of repaglinide and metformin would provide safety and efficacy comparable to that of repaglinide and metformin administered as separate formulations.