Hyperbranched poly(esteramides) as solubility enhancers for poorly water-soluble drug glimepiride

The aim of this work was to study the feasibility of using hyperbranched polymers with highly branched structure and a large number of functional groups as solubilization enhancers for poorly water-soluble drugs. Antidiabetic drug glimepiride was used as a model drug and commercially available hyperbranched poly(esteramide)s as drug carriers.The results of in vitro dissolution studies showed significantly enhanced aqueous-solubility of glimepiride in the form of solid dispersions with hyperbranched poly(esteramide)s as compared to pure glimepiride in crystalline or amorphous form. The results of IR spectroscopic measurements revealed that improved solubility is a consequence of a complex formation between glimepiride and hyperbranched polymer. HB poly(esteramide)s with carbonyls of ester (O)–CO and amide (N)–CO groups serve mainly as a source of proton acceptor groups to which NH groups of glimepiride establish hydrogen bonds. Due to complex formation, glimepiride is within solid dispersions with HB polymers amorphous up to concentration of 5% (w/w) as revealed by X-ray powder diffraction measurements. Above this limit, glimepiride crystallizes as a separate phase during solvent evaporation.