This study investigated the solubilization of cyclosporin A (CsA), a neutral undecapeptide, by cosolvency, micellization, and complexation. Cosolvents (ethanol, propylene glycol, polyethylene glycol, tetrahydrofurfuryl alcohol polyethyleneglycol ether, and glycerin), surfactants (polyoxyethylene sorbitan monooleate [(Tween 80)], polyoxyethylene sorbitan monolaurate [(Tween 20)], and Cremophor EL), and cyclodextrins (α-cyclodextrin [(αCD)] and hydroxypropyl-β-cyclodextrin[(HP\CD)] were used as solubilizing agents in this study.
Surfactants had a noticeable effect in increasing CsA solubility. Twenty percent solutions of Tween 20, Tween 80, and Cremophor EL increased the solubility by 60 to 160 fold. Cyclodextrins can increase the CsA solubility, but αCD was more effective than HP\CD. Cosolvents on the other hand did not increase the solubility of CsA as much as expected from the LOGP (logrithm of wateroctanol partition coefficent) value of CsA.
KeyWordsCyclosporin A Conformation Solubility Solubilization
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