Uptake of water by excipients in tablets

Abstract

Disintegrants such as sodium starch glycolate (NaSt glycolate), crospovidone (PVPP) and silicon dioxide (SiO 2) play an active part in influencing water uptake and disintegration time ( DT) of sulphanilamide tablets containing methylcellulose (MC) of varying viscosity grade as a binder. The disintegrants used were at the 1.25%, 2.50% and 5% level. The DT of tablets containing NaSt glycolate decreased with an increase in the viscosity of MC due to enhanced water uptake. Tablets without MC but only the drug and NaSt glycolate were observed to have a higher DT and lower water uptake at higher concentrations of the disintegrant. With PVPP, the DT increased with increasing viscosity of MC. This occurs despite an increase in water uptake by tablets containg higher viscosity MC. For tablets containing SiO 2 and MC, DT is extremely high. In the absence of MC, water uptake is slightly higher with the higher concentration of SiO 2 but DT still remained high. Water uptake alone does not determine the disintegration process. The choice of excipients, especially binders such as methylcellulose, plays a crucial role in influencing disintegrant action.