A method of producing pharmaceutical grade bretylium tosylate comprising low amounts of mutagenic impurities. The method comprises forming bretylium tosylate having a purity of less than 99.5% and purifying the bretylium tosylate by: i) forming a slurry of the bretylium tosylate with a mixture of acetone and ethyl acetate; ii) filtering the slurry to obtain purified bretylium tosylate. The bretylium tosylate so produced has a purity of at least 99.5%, and suitably comprises less than 0.5 ppm of the potentially mutagenic impurity ethyl p-toluenesulfonate. The bretylium tosylate so produced also suitably comprises less than 0.5 ppm of the potentially mutagenic impurity 2-bromobenzylbromide.