Abstract
The effect of the constitution rate of zine oxide ointment (ZO) in the various mixtures of Rinderon DP ointment (RDPO) and ZO on the release of betamethasone dipropionate (BM-DP) was studied. Zinc oxide was added in the concentrations of 0, 10 and 20% to the vehicle of beeswax and soybean oil, which were mixed in the ratio of 20: 70, 25: 65 and 30: 60, to obtain ZO in nine different concentrations for determination of the viscosity, penetration and extensibility. The release of BM-DP from the ointment containing equivalent volumes of ZO and RDPO were measured by HPLC.
The release of BM-DP fitted well into Higuchi's equation, and was shown to be linear in function against square root of time. The release rate constant (K) was greater for mixtures in any of the aforementioned constitution rates than that for RDPO alone. Furthermore, K increased specifically when the content of beeswax was less, soybean oil greater and zinc oxide content greater. However, there was no correlation between the material value of ZO and the rate constant K, suggesting that this increase is attributable to the interactions of constituents of ZO.
As a result, it was suggested that the therapeutic effect might be expected of ZO containing 10 to 20% of zinc oxide, as it retained the physical integrity as an ointment and allowed good release of steroids when mixed with a steroid ointment.
