Stability of sulfur mustard in vehicles suitable for cutaneous exposure of swine

Sulfur mustard (SM) is a blistering chemical warfare agent capable of forming deep, bullous lesions in man that heal very slowly and tend to become infected. We have developed a swine model that is used to evaluate candidate treatment regimens for the SM injury. To expand our wound-healing studies, SM mixtures suitable for cutaneous exposure were needed so that a large total body surface area (TBSA) could be covered during the SM application. The vehicles selected for use in the SM exposure experiments would have to be miscible with SM, form a stable mixture, be soluble in an organic solvent that is required for the stability evaluation, be nontoxic, and not interfere with the SM reaction on the skin. Four candidate vehicles were selected for testing. The vehicles were peanut oil, propylene glycol, polyethylene glycol (PEG) 200, and PEG 400. During preliminary screening, PEG 400 was eliminated as a candidate because it was not soluble in hexane, and least soluble in chloroform and methylene chloride. Propylene glycol was eliminated since it did not mix with SM. The SM mixtures of peanut oil and PEG 200 were prepared for stability testing over the 25–75% SM concentration range. The results show that the SM mixtures prepared with peanut oil and PEG 200 at the 25, 50, and 75% levels are stable for more than 8 days when stored at 21°C (room temperature) and more than 35 days when stored at −70°C (freezer).