Development and pharmaceutical approach for sustained-released metformin succinate tablets

Metformin is currently marketed in the U.S. and worldwide as a hydrochloride salt and sustained-release (SR) tablets are preferred for increasing patient compliance. However, this SR tablet is large because of its high water solubility and the high dose required for efficacy, and some patients find it difficult to swallow. To overcome these challenges, the salt formation was changed, thereby changing its solubility. Ten new pharmaceutical salts were synthesized and metformin succinate was chosen among these because of its lower solubility and lower molecular weight. DSC thermograms and FT-IR spectra demonstrated that metformin HCl and succinate were different materials. However, other tablet properties related to effectiveness, such as density, compressibility, particle size distribution, stability in various artificial human fluids, and permeability were not statistically different. Metformin succinate SR tablets with an excipient portion reduced from 43% to 14% were prepared and compared with metformin HCl SR tablets in vitro and in vivo. The drug release study in buffer solutions at pH 6.8 and the pharmacokinetic parameters, Cmax, Tmax, and AUC0−∞ showed no significant differences between the two types of tablets. In conclusion, metformin succinate, which has low water solubility, can be used to reduce the size of SR metformin tablets for improving patient compliance.

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