Slow release of chloroquine phosphate from multiple taste-masked W/O/W multiple emulsions.

The efficacy and safety of chloroquine as an antimalarial has contributed to the survival of millions in the past 50 years. Chloroquine is widely available, cheap, well tolerated and orally well absorbed. Therefore, it remains an important antimalarial drug. However, on oral administration, particularly to children, the unpleasant taste is a problem. This could be avoided by 'taste-masked and controlled release' formulations such as multiple emulsions. Although Plasmodium falciparum has developed resistance to many antimalarial drugs, including chloroquine, resistance may be attributed, among other factors, to subclinical dosage of chloroquine from administered pharmaceutical forms. This could also be relevant in the treatment of rheumatoid arthritis. Multiple W/O/W emulsions of chloroquine phosphate were prepared. Assessment of emulsion stability showed no significant change in the system. Prolonged storage (four months) of the emulsion resulted in negligible loss of chloroquine phosphate. The results suggest, therefore, that chloroquine phosphate releases due to diffusion of the drug from the internal globules and not as a consequence of instability of the W/O/W emulsion. These characteristics are in accordance with the requirements for controlled release pharmaceuticals. Stability of multiple emulsions could have resulted from interfacial polymerization or complexion between molecules. Release assessments showed faster rates for W/O/W emulsions which had smaller internal aqueous globules and, therefore, an increased interfacial area. Furthermore, transport of high-diffusion coefficient micelles could have given a greater solute flux in these systems.