Polyvinyl methyl ether maleic anhydride

Mortada (1981) prepared microcapsules of phenacetin using the polymer n-butyl half ester of polyvinyl methyl ether maleic anhydride). The optimum conditions for coacervation were determined from a triangular phase diagram. Sodium acetate was used to dissolve the polymers in water and sodium sulfate was used to effect coacervation. The optimum conditions were polymer 0.5-3%, total salt 6.5%. During the microencapsulation of phenacetin, the coacervate drops tended to deposit on the surface of the drug suspended in the system. Gradual addition of sodium sulfate resulted in the continuous deposition of the coacervate onto the coated drug particle. As the core to coat ratio increased, the mean diameter of the microcapsules decreased slightly. However, the time required for the maximum amount of drug to be released decreased. Drug release was enhanced as the pH of the dissolution medium increased.

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