For the purpose of investigating of its suitability for topical application, the stability of sisomicin incorporated in hydrophilic petrolatum was investigated under various storage conditions by high-performance liquid chromatography. Sisomicin was extracted from the oleaginous vehicle, which was kept in a liquid state by adding liquid paraffin, using pH 6.5 phosphate buffer. An appropriate retention behavior of the antibiotic is obtained on a μ Bondapak-C18 column with a mobile phase of 2.0% (w/v) sodium sulfate-0.005 m sodium 1-pentanesulfate (detection at 214 nm). The degradation of sisomicin follows first-order kinetics with regard to the remaining antibiotic in aqueous solution: the apparent first-order rate constants are 2.63 xl0-3d-1at 5 °C and 1.70 x 10-2d_1 at 25 °C. When incorporated in hydrophilic petrolatum, the antibiotic is 5 to 7 times more stable than in an aqueous medium. This is due to the reduction of its surface oxidation. Accordingly, the ointment is therapeutically effective for at least 3 months when preserved under shielding from light at 5 °C.
All Science Journal Classification (ASJC) codes
- Drug Discovery