Purpose: A process of melt granulation whereby the drug powder is mixed with a melted wax has been used to modify the dissolution rates of drug particles. The present study investigated how the incorporation of hydrophobic materials (talc or magnesium stearate) in the core of such granules may further retard drug release.

Method: The hydrophobic powder was mixed with the drug (paracetamol) powder prior to melt granulation with Carnuba wax. Content of the hydrophobic material varied from 0 to 50% but the content of wax was constant. Conventional granules of paracetamol were formed by wet massing the paracetamol powder with starch mucilage 20%w/v, followed by screening and drying. The granules were subjected to dissolution test.

Results: The results indicated that melt granulation remarkably retarded the dissolution rates of paracetamol granules. The rates can be further retarded by inclusion of an internal hydrophobic material. The dissolution rate of the conventional granules was 32%h^-1 as against 11.6%h^-1 (melt granules) and 10.3%h^-1 (melt granules with intragranular hydrophobic agents, 5%w/w).

Conclusion: The indication is that the inclusion of an intragranular hydrophobic agent in the melt granules can be used to obtain further control of drug release

Keywords:  carnuba wax, controlled release, talc, and magnesium stearate.

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