In vitro release of anthralin from white petrolatum and an o/w cream

A method to study the in vitro release of anthralin from ointments was developed. A diffusion cell with an artificial membrane (dialysis membrane) was used. As the solubility of anthralin in water is extremely low, methanol was chosen as receptor phase. The temperature at the membrane was kept constant at 32 degrees C during the release study. At appropriate intervals samples were withdrawn and assayed by HPLC. The in vitro release of anthralin from white petrolatum and a cream containing 70% oil in water (Locobase) was studied in a concentration range of 0.04-3.0%. Both ointments showed a faster release with increasing concentration of anthralin. The in vitro release of anthralin from the cream was significantly faster than from white petrolatum.