A comparative rheological study on carbopol viscous solutions and, the evaluation of their suitability as the ophthalmic vehicles and artificial tears.

Abstract

The rheological behaviours of different types of Carbopol (Carbopol 940, 934, 941 and 910) were investigated in the present work. Viscous solutions of these polymers were prepared in the range of concentration between 0.01-0.25% (w/w). 10% aqueous solution of sodium hydroxide was used for the neutralization procedure. Mannitol, sorbitol, sodium chloride and borate were tested to make the isotonic solutions. The viscosities of the solutions decreased dramatically with sodium chloride and sodium borate. Mannitol had no effect on the pH values of the solutions while sorbitol has showed a small effect. The solution prepared were sterilized by autoclaving and stored at 4 degrees C for 3 months. The pH value, viscosity and osmolality measurements were made after neutralization and sterilization, at the end of 1 and 2 weeks, 1, 2 and 3 months of storage. It could be concluded that four types of Carbopol are suitable for ophthalmic use. The aqueous vehicles of Carbopol 940 had an excellent appearance and clarity when compared with the other types of polymer.