Identification of the mebendazole polymorphic form present in raw materials and tablets available in South Africa

A preformulation study of four different raw materials of mebendazole showed that three samples were polymorph C and the other polymorph A, or a mixture of form A and B. X-ray powder diffractometry and infrared spectroscopy indicated that this powder could be form B, but powder dissolution, for which a much slower dissolution was obtained, suggests polymorph A. Literature prescribes the use of polymorph C pharmaceutically, but generic manufacturers should be aware that forms other than C are still available on the market. The four mebendazole tablets currently available in South Africa were also tested and it was found that all of them contained polymorph C.