Release of chlorpheniramine maleate from fatty acid ester matrix disks prepared by melt-extrusion

Chlorpheniramine maleate was incorporated into disks consisting of glyceryl fatty acid esters, polyethylene glycol fatty acid esters or a combination of the two. A melt-extrusion process was used to prepare the matrix disks containing the drug. The release of the drug into distilled water, pH 1.2 buffer, and pH 7.5 buffer showed the expected square root of time dependence. An increase in the fatty acid ester hydrophilic-lipophilic balance (HLB) from 1 to 14 resulted in a 10-fold increase in the drug release rate from 0.25 +/- 0.01 to 25.84 +/- 1.29 mg cm-2 h-1/2. The maximum release rate was seen from the fatty acid ester with a melting point of 44 degrees C. The pH of the dissolution medium had a small impact on the rate of drug release, but the rate of agitation had no significant influence on the rate of drug release. By blending a fatty acid ester of a high melting point (64 degrees C) and a low HLB value of 2 with esters of lower melting points (33 to 50 degrees C) or higher HLB values (10 to 14), it was possible to modify the release from 10.0 +/- 0.70 to 21.5 +/- 0.57 mg cm-2 h-1/2.