Release of Tolmetin from Carbomw Gel Systems

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Abstract
Gel-formulations containing a nonsteroidal anti-inflammatory drug, tolmetin, were prepared using three different carbomers namely, Carbopol™ 934, 940 and 941. Effects of cosolvent composition, carbomer type, carbomer concentration and drug concentration on drug release from the gels were analyzed by factorial design. Gels with high aqueous content yielded significantly higher tolmetin release rates than gels with lower aqueous content. Although no significant differences in drug release characteristics were observed between the three carbomer gels, there was a trend in the release profiles; fastest drug release was observed from Carbopol™ 941 gels and the slowest drug release was observed from Carbopol™ 940 gels. Increasing the carbomer concentration from 1% w/w to 2% w/w had no significant effect on drug release from gel formulations prepared with all the three different types of carbomers. However, increasing the tolmetin concentration in the gels from 1% w/w to 4% w/w resulted in a dramatic increase in drug release. An investigation of the mechanism of drug release from the gels revealed that tolmetin release was diffusion controlled, except at the outset.