Microencapsulation of astiban acid for the treatment ofSchistosomiasis mansoni

Schistosomiasis is among the top five diseases in the world in terms of morbidity, affecting perhaps 200 million people in tropical and subtropical countries. Antischistosomal drugs are toxic and rapidly metabolized. Hence, they must be given in a number of spaced doses. In spite of this there are severe side effects leading to poor patient compliance. This is an ideal situation for the application of sustained drug release to avoid the toxic peak concentration of drug. This study was carried out using Astiban acid, an antimonial drug that is effective againstS. mansoni. Unfortunately, the drug is sufficiently soluble that 50 mg will dissolve in 100 mL water in less than a minute. To permit sustained release of intramuscularly injected drug, microcapsules of astiban acid in poly(d,l-lactic acid) were formed by coacervation. Release studies show that an appreciable fraction of the drug is available at the surface for rapid solution. After this surface drug dissolves, the remaining drug is released slowly with half-times of many hours. After the initial burst, the release of drug follows Higuchi’s equation up to approximately 80% release, with exponentially decreasing release rates thereafter.