1H-NMR spectroscopic study of cysteamine eyedrops

Abstract

The efficiency of cysteamine eye drops in the treatment of cystinosis has been demonstrated in several studies: Corneal cystine crystals can be removed by topical cysteamine. Cysteamie 0.5% eye drops were superior to a 0.1% solution. It is not clear how fast cysteamine is oxidized to cystamine under the influence of atmospheric oxygen. Samples of a new bottled cysteamine 0.5% solution were analysed 1H-NMR-spectroscopically over a period of several weeks (AM 400/WB-NMR-instrument, Bruker/Karlsruhe; 400.15 MHz). Samples bottled in an argon atmosphere were compared to samples bottled without inert gas. Definite samples were opened four times a day (A). The remainder of the samples was stored closed (B). In sample A a 1:1 weight ratio between cysteamine and cystamine was reached after 38 days. In samples B cysteamine was not oxidized to cystamine. The initial amount of cystamine was something lower in samples with argon, but argon could not prevent the decrease of the cysteamine concentration in sample A. The preparation of cysteamine solution in an argon atmosphere is useful. One bottle can be used for about one week, if less than 10% of the oxidation product cystamine is accepted.