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The stability of clobetasol propionate 0.05 percent spray and lotion and calcipotriene ointment 0.005 percent in co-mixture was investigated in a laboratory assay study. Measurements of the active ingredients showed no loss of potency of clobetasol or calcipotriene in analyses performed up to 120 hours post-mixing.
Fort Worth, Texas - Results from a laboratory study designed to investigate chemical compatibility of commonly combined topical psoriasis medications indicate that patients can apply clobetasol propionate spray or lotion 0.05 percent (Clobex, Galderma) conveniently with calcipotriene ointment 0.005 percent (Dovonex, Warner Chilcott) without concern about loss of potency of either product, reports Ronald W. Gottschalk, M.D., medical director, Galderma Laboratories, Fort Worth, Texas.
In the study, clobetasol propionate spray and lotion, along with another previously tested and commercially available corticosteroid product (serving as a control) - halobetasol propionate cream 0.05 percent (Ultravate, Bristol-Myers Squibb) - were each mixed in equal quantities with calcipotriene ointment. Samples were maintained at 32°C and concentrations of the corticosteroid and calcipotriene in each mixture were measured using high performance liquid chromatography (HPLC) at predetermined time points ranging from five minutes to 120 hours post-mixing.
CLOBETASOL REMAINS STABLE
There was also no significant change in the concentration of calcipotriene in those mixtures over time. In the halobetasol-calcipotriene mixtures, the concentration of halobetasol remained stable. There was a significant decrease in the potency of calcipotriene, although it was numerically small and believed to be clinically insignificant, Dr. Gottschalk says.
"Clobetasol spray was approved by the FDA in late 2005. Thereafter, we were contacted by a number of physicians who were inquiring about potential compatibility issues with calcipotriene ointment. This study was undertaken to respond to the needs and concerns of the marketplace, and the results provide prescribers data to support recommendations about the concomitant application of our clobetasol propionate products with calcipotriene ointment," Dr. Gottschalk tells Dermatology Times.
In developing the protocol, Dr. Gottschalk and his collaborators contacted Mark Lebwohl, M.D., who had previously published research on the stability of calcipotriene combined with several other topical psoriasis therapies (J Am Acad Dermatol. 1998; 38:1010-1011). Halobetasol propionate cream 0.05 percent represented one of the products included in that study, and it was found to be compatible with calcipotriene.
"As there was information available about the stability of halobetasol cream and calcipotriene ointment when mixed, we included that combination as a positive control in our investigation.
"Our results are consistent with Dr. Lebwohl's research and provide validation of our testing method," Dr. Gottschalk says.
"One change from Dr. Lebwohl's approach was to maintain the samples at 32°C to more closely approximate the physiologic temperature of the skin."
The two products in each combination tested were mixed in a small glass container, and the combinations were created by placing the corticosteroid product into the container first followed by the calcipotriene, and vice versa. The results were similar regardless of the order of addition of the products, and there was no physical evidence of incompatibility based on visual inspection of the samples.