Compatibility of desoximetasone and tacrolimus

The physical and chemical compatibility of desoximetasone ointment 0.25% and tacrolimus ointment 0.1%, both widely used to treat atopic dermatitis, were determined. A 1:1 (w/w) mixture of desoximetasone ointment 0.25% (Topicort, Taro Pharmaceuticals USA, Inc.) and tacrolimus ointment 0.1% (Protopic, Fujisawa Healthcare, Inc.) were prepared and stored under three different temperature/relative humidity conditions: 25 degrees C/60% RH; 30 degrees C/60% RH; and 40 degrees C/75% RH. Unmixed ointments stored under the same temperature and humidity conditions as the mixture served as controls. Samples were evaluated at days 1, 2, 7, 14, and 28 for color, degree of physical separation, and chemical stability via reverse-phase high performance liquid chromatography. Ranges of relative recovery for each active ingredient for all storage conditions ((% Mixture/% Control) x 100) were 89.6-109.3% for tacrolimus and 99.0-103.4% for desoximetasone. No significant difference in physical appearance or chromatographic profile between the mixture and controls was observed. Therefore, we conclude that desoximetasone ointment 0.25% (Topicort) and tacrolimus ointment 0.1% (Protopic) are physically and chemically compatible up to four weeks when mixed in a ratio of 1:1 (w/w).