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The stability and blanching efficacy of betamethasone-17-valerate in emulsifying ointment

1982; Oxford University Press; Volume: 107; Issue: 1 Linguagem: Inglês

10.1111/j.1365-2133.1982.tb00292.x

1365-2133

K.S. Ryatt, J. W. Feather, A. C. Mehta, J. B. Dawson, J.A. COTTERILL, R. Swallow,

Systemic Sclerosis and Related Diseases

The bio-availability of betamethasone-17-valerate (Betnovate ointment) in emulsifying ointment (1 in 4 dilution) was investigated in ten subjects using a single-application vasoconstrictor assay; the blanching induced was measured using a skin reflectance spectrophotometer. The vasoconstrictor activity of the diluted preparations decreased with age. There was no significant difference between the vasoconstrictor activity of freshly made Betnovate 1 in 4 in emulsifying ointment and undiluted Betnovate ointment, and between 3-4 week old diluted Betnovate and emulsifying ointment base. Blanching induced by freshly prepared 4, 8 and 16-fold dilutions was not significantly different but a large reduction in blanching occurred on diluting 32-fold with emulsifying ointment. The degradation of betamethasone -17-valerate in emulsifying ointment was quantified by high performance liquid chromatography. More than 60% of the betamethasone -17-valerate underwent degradation within 6 h. There was a simultaneous increase in the concentration of betamethasone-21-valerate which peaked within 2 days and was followed by a slow degradation (half-life 8 days) to betamethasone free alcohol.