تصنيع ودراسة لمواصفات الأدوية المساعدة المصممة لمادة الغايفينيسين
Synthesis and Characterization of Designed Guaifenesin Prodrugs
أمين محمود عبد المنعم ثوابته
Amin Mahd A. Thawabteh
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Guaifenesin is an extremely bitter taste substance which affects its usage in pediatric and geriatric formulations. In this thesis we aimed to mask the bitter taste of guaifenesin by converting it to a potential tasteless prodrugs using different linkers. The prodrugs were synthesized by esterification of carboxylic acid anhydrides and guaifenesin. Maleic anhydride, succinic anhydride, and glutaric anhydride, respectively, were used to synthesize guaifenesin ester prodrugs (guaifenesin maleate, guaifenesin succinate, guaifenesin glutarate), 1 H-NMR, LC-MS, and FT-IR have confirmed the identity and purity of the new prodrugs. In vitro kinetic studies for the above mentioned prodrugs were done in four different aqueous media: 1 N HCl and buffers pH 3.3, pH 5.5 and pH 7.4. Under the experimental conditions the target prodrug was hydrolyzed to release the parent drug, guaifenesin, as was confirmed by HPLC determination. The kobs and the corresponding t1/2 values for guaifenesin prodrugs in 1N HCl were calculated from the linear regression equation correlating the log concentration of the prodrug versus time. The rate constant (kobs) was found to be 7.2x10-4 for guaifenesin maleate prodrug, 2.54x10-4 guaifenesin succinate prodrug, and 2.36x10-4 guaifenesin glutarate prodrug. Half-lives values (t1/2) were 2.01 hours for guaifenesin maleate prodrug, 7.03 hours for guaifenesin succinate prodrugs, and 7.17 hours for guaifenesin glutarate prodrug. On the other hand, at pH 3.3, 5.5 and 7.4, guaifenesin maleate, guaifenesin succinate, and guaifenesin glutarate prodrugs were entirely stable and no release of the parent drug, guaifenesin, was observed.