Effect of EDTA and Methionine on Preventing Loss of Viscosity of Cellulose-Based Topical Gel

Methylcellulose and hydroxypropylmethylcellulose (hypromellose) are used in topical formulations of a protein to form a viscous hydrogel. Five lots of hypromellose raw material were made into 3% gel; all showed viscosity loss after sterilization by autoclave. EDTA (edetate disodium) minimized the viscosity loss caused by autoclaving in the presence of up to 100 ppm H 2 O 2 . These results suggest that EDTA may prevent loss of viscosity of the hydrogel when peroxide is present. H 2 O 2 at low levels (2–50 ppm) caused significant viscosity loss over time at either 40°C or 5°C in 3% methylcellulose or hypromellose gel. EDTA slowed the rate of viscosity loss during storage under stress by H 2 O 2 but did not completely prevent the loss. Methionine was effective in completely preventing gel-viscosity loss during storage in the presence of up to 50 ppm H 2 O 2 . On the basis of these results, it is recommended that methionine be added to the protein topical formulation as a stabilizer against viscosity loss.