Cation exchange resins as pharmaceutical carriers for methylene blue: binding and release.

Methylene blue is a competitive inhibitor of the glutathione reductase of Plasmodium falciparum and is used in combination with other antimalarial drugs leading to a renaissance of methylene blue in malaria therapy. Its bitter flavour and tissue colouring property impair compliance, especially in children. These problems may be solved by binding the cationic methylene blue to cation exchange materials as pharmaceutical carriers in order to mask the undesirable properties. However, such carriers are only useful if the antimalarial is released under physiological conditions. The binding to seven cation exchange resins was studied. Ion exchangers on acrylic or methacrylic acid basis bound between 1.54 and 2.16 g methylene blue chloride trihydrate per gram ion exchanger. Polymers on divinylbenzene or styrene basis with sulphonic acid groups bound 306 and 384 mg of methylene blue chloride trihydrate per gram ion exchanger. In aqueous solution at pH of 1.5, nearly all bound methylene blue was released. The release of methylene blue from (meth)acrylic acid polymers in the presence of proteins and fat was not affected. From these data ion exchangers present a promising group of pharmaceutical carrier for the safe and compliant drug administration of methylene blue to children.