Antimony Content and Toxicity of Urea Stibamine

UREA STIBAMINE, introduced by Brahmachari1in 1922 and widely employed in the treatment of kalaazar in India and elsewhere, still remains a compound with no definitely known and agreed chemical formula. It was originally reported to be a substance composed of urea and para-aminophenylstibinic acid with the empirical formula, C7H12O4N3Sb. Later it was suggested that the compound was identical with ammonium-para-carbamidophenylstibinate, NH2.CO. NH.C6H4.SbO(OH).ONH42. Ghosh et al.3and Gray et al.4gave definite evidence that urea stibamine was not a single substance of definite composition and the latter group of workers showed that the ‘effective active principle’ was a di-substituted urea, S-diphenyl-carbamide-4:4 distibinic acid. The antimony content of various commercial samples was shown by Ghosh et al. to vary between 20 and 43 per cent, while Gray et al. reported a comparatively smaller range of variation in antimony content from 44.19 to 48.6 per cent. Brahmachari5appeared to have accepted the results of Gray et al. in this regard, and emphasized that the divergent results obtained by different investigators were due to different brands of “so-called urea stibamine”, not conforming to his original specifications, being put on the Indian market.