Passage of somatostatin analogue across human and mouse skin

Recent studies have documented beneficial effects of the somatostatin analogue, SMS 201-995 (hereafter referred to as SMS), when administered subcutaneously to patients with a variety of disorders. Since SMS is a small peptide, we tested the ability of two penetrant enhancers-dimethylsulfoxide and N-decylmethylsulfoxide (C₁₀MS)-to promote transcutaneous passage of SMS. Samples of skin from human cadavers and hairless mice were tested in a static diffusion chamber. Application of SMS in conjunction with 1% C₁₀MS resulted in rapid transdermal passage of SMS. These data were confirmed for hairless mouse skin in experiments with a modified diffusion chamber having continuous flow-through of receptor fluid in the subdermal reservoir. In this system, the cumulative amount of SMS that permeated hairless mouse skin was 20 μg/cm²/24 hours. Topical application of SMS with C₁₀MS beneath a patch to mice confirmed in vitro data. Topical application of 10 μg of SMS resulted in plasma SMS levels of greater than 8,000 pg/ml within 2 hours. We conclude that SMS will cross both human and mouse skin, with a clinically significant flux, when administered topically with C₁₀MS. The data support the feasibility of in vivo human trials of topical SMS therapy.