Water Inclusion Effect on Starch 1500 As an Excipient Used in the Production of the Oral Solid Dosage Form

Starch 1500 is a well-known diluent, binder, disintegrant and dissolution enhancer, which is widely used in the formulation of the oral solid dosage forms. To validate the proposed hypothesis that whether Starch 1500 preserves the chemical hydrolysis of the moisture sensitive drugs, the understanding the sorption-desorption behavior of this excipient is the first challenge. Water molecules when interacting with most of the pharmaceutical excipients and APIs localize within the crystalline part of the physical structure. Specifically, for starch-based excipients, crystal regions of the structure host the water molecules within the double-stranded helices of the crystallite. DSC TGA, FTIR-ATR and NIR techniques were adopted to determine the freezable and non-freezable bound water with starch 1500, both qualitatively and quantitively. Among different mathematical models, Young and Nelson model have not well practised compared to the other available models, such as BET, GAB, Oswin and Smith models. It was found out that Young and Nelson model along with the GAB theory well carver the sorption isotherms. The variable parameters obtained from these two equations were compared and the monolayer value was estimated. The amount of monolayer coverage with the assumption of the strength of the binding of the water molecules on the first accumulated layer was correlated with the total water content of the Starch 1500. Analysis of the strength of the hydrogen bonds between Starch 1500 and the water molecules, mobility and the availability of the reactive water molecules to take part in chemical hydrolytic reactions could be explained.