Formulation and evaluation of mebendazole dosage forms

Abstract

Parasites in the restricted sense are those members of the animal kingdom which derive their means of well-being from other members of the animal kingdom, at the same time depriving their host of some (sometimes all) of its well-being. Parasitic diseases are much more widespread than many people realise. These diseases affect not only impoverished people in remote countries but they can be important health problems for rich and poor throughout the world. Different parasites infect our domestic animals and cause great losses; they have a great influence on the growing, production and overall resistance against other diseases. The best solution to the problem rests in preventing these infections rather than in wring them. They are never beneficial and we must control them effectively. Mebendazole is a synthetic benzirnidazole with a wide spectrum of anthelmintic activity. Three polymorphic forms of mebendazole, identified A, B and C can be formed through controlled crystallisation procedures. Polymorph C is apparently pharmaceutically favoured. It has been clearly demonstrated that a correlation exist between the polymorphism of the active substance and the bioavailability of the finished product. The characterisation of the active substance was done by means of infrared spectroscopy, DSC and X-ray powder diffraction. The first aim of this study was to formulate a chewable tablet appropriate for the multi-dosage of children during a de-worming program. Chewable tablets present an attractive alternative for children who have not yet learned to wash tablets down with water. The second aim was to formulate a gel for dogs and domestic animals which is more viscous than the products on the market. Dosing an animal with a liquid can be difficult, and a sudden movement of the animal often results in spillage. A drug in a gel form is a convenient means for administration to pets, to reduce spillage. Stability tests were carried out over a test period of three months at 5⁰C, 25°C + 60% RH and 40°C + 75% RH storage conditions for both dosage forms. All the tests complied with the acceptable criteria except for the loss on drying tests done on the chewable tablets. Therefore silica gel should accompany the tablets to prevent this problem. An HPLC method was developed and validated for the simultaneous determination of the preservative, potassium sorbate and the active substance, mebendazole.