Naproxen glycine conjugate-synthesis, pharmaceutical preformulation and pharmacodynamic evaluation

The project was aimed at synthesizing and characterizing amino acid conjugate of naproxen (categorically stated as Type II A prodrug) that is expected to enhance solubility without affecting permeability and is capable of delivering naproxen (NAP) to colon without significant reversion of prodrug in gastrointestinal conditions. Thus, naproxen-glycine conjugate (NAP-GLY) was prepared by conventional coupling method and the prodrug was characterized by FTIR, FTNMR, FAB mass and elemental analysis. The conjugate was then subjected to selected pharmaceutical preformulation studies like pH-solubility analysis, intrinsic dissolution rate and pH partition studies. These studies established 1.24 folds higher solubility of the (NAP-GLY) over NAP in phosphate buffer pH 7.4 without compromising its partitioning ability. The amino acid conjugate demonstrated superior intrinsic dissolution capabilities (30.9% enhancement) than NAP and in vitro reversion studies suggested its potential of safe transit to colon where the moiety is capable of reverting to 78.52% NAP after 72 hrs of the experiment. In vivo evaluation of NAP-GLY in experimentally induced colitis established its efficacy an anti-inflammatory prodrug moiety (ulcer index = 6.73 with respect to 42.5 for control) that was supported by histological studies. In addition to its ability to control colonic ulcers NAP-GLY demonstrated insignificant (P >0.05) gastric ulcerogenic potential. Conclusively, the conjugate when suitably formulated can be considered as therapeutically efficacious drug delivery system with fewer pharmaceutical limitations.