Formulation and Evaluation of Bioadhesive Cyproheptadine Tablets

Purpose: To evaluate the effect of formulation variables on the bioadhesion and release properties of bioadhesive cyproheptadine hydrochloride tablets.Methods: Screening of polymers - hydroxypropyl methylcellulose, (HPMC), sodium carboxy methyl cellulose (CMC), and Carbopol 974p and 934p - in solution form were carried out by shear stress and detachment force measurement,based on Taguchi model, in order to determine their bioadhesion properties. Central composite design (CCD) was applied to optimize the combined effects of the polymers on release rate constant (K), diffusion coefficient (n), regression coefficient (R2) and detachment force of a sustained release tablet formulation of cyproheptadine hydrochloride containing also a prompt dose of the drug.Results: The shear stress of 3 % solution of HPMC was greater than that of an equivalent concentration of Carbopol 934P. The values of K, n, R2 and detachment force for the optimized formulation (F0) were 0.269, 0.696, 0.964 and 0.066 Newton (N), respectively, and showed good correlation with the predicted values, thus confirming the practicability and validity of the model.Conclusion: Gastric retention time can be increased for cyproheptadine hydrochloride by formulating it as a bioadhesive tablet that enhances the retention of the dosage form in the stomach and hence gastric absorption of the drug.Keywords: Cyproheptadine hydrochloride, Bioadhesive core tablet, Detachment force, Taguchi design, Central composite desig

Comparison of verona integron-borne metallo-β-lactamase (VIM) variants reveals differences in stability and inhibition profiles

Metallo-β-lactamases (MBLs) are of increasing clinical significance; the development of clinically useful MBL inhibitors is challenged by the rapid evolution of variant MBLs. The Verona integron-borne metallo-β-lactamase (VIM) enzymes are among the most widely distributed MBLs, with &gt;40 VIM variants having been reported. We report on the crystallographic analysis of VIM-5 and comparison of biochemical and biophysical properties of VIM-1, VIM-2, VIM-4, VIM-5, and VIM-38. Recombinant VIM variants were produced and purified, and their secondary structure and thermal stabilities were investigated by circular dichroism analyses. Steady-state kinetic analyses with a representative panel of β-lactam substrates were carried out to compare the catalytic efficiencies of the VIM variants. Furthermore, a set of metalloenzyme inhibitors were screened to compare their effects on the different VIM variants. The results reveal only small variations in the kinetic parameters of the VIM variants but substantial differences in their thermal stabilities and inhibition profiles. Overall, these results support the proposal that protein stability may be a factor in MBL evolution and highlight the importance of screening MBL variants during inhibitor development programs.</p

Comparison of verona integron-borne metallo-β-lactamase (VIM) variants reveals differences in stability and inhibition profiles

Metallo-β-lactamases (MBLs) are of increasing clinical significance; the development of clinically useful MBL inhibitors is challenged by the rapid evolution of variant MBLs. The Verona integron-borne metallo-β-lactamase (VIM) enzymes are among the most widely distributed MBLs, with >40 VIM variants having been reported. We report on the crystallographic analysis of VIM-5 and comparison of biochemical and biophysical properties of VIM-1, VIM-2, VIM-4, VIM-5, and VIM-38. Recombinant VIM variants were produced and purified, and their secondary structure and thermal stabilities were investigated by circular dichroism analyses. Steady-state kinetic analyses with a representative panel of β-lactam substrates were carried out to compare the catalytic efficiencies of the VIM variants. Furthermore, a set of metalloenzyme inhibitors were screened to compare their effects on the different VIM variants. The results reveal only small variations in the kinetic parameters of the VIM variants but substantial differences in their thermal stabilities and inhibition profiles. Overall, these results support the proposal that protein stability may be a factor in MBL evolution and highlight the importance of screening MBL variants during inhibitor development programs.</p