For drugs with different mechanisms of action, Dr. Pariser says, vehicles often differ significantly, yielding a significant vehicle effect.
“And we don’t know what that effect is in extemporaneously compounded preparations,” he says.
In a meta-analysis of seven clinical trials of combination topicals for psoriasis, for example, adding a class I or class II steroid to a vitamin D analog increased the likelihood of clearance by 28% and 14%, respectively, versus vitamin D analog monotherapy. But adding a class III corticosteroid produced no additive effect. The overall impact of adding any class corticosteroid was a 20% improvement over vitamin D monotherapy.
Compared to fixed-combination products, says Dr. Pariser, extemporaneously compounded vitamin D-steroid combinations allow treatment regimen flexibility and may reduce corticosteroid usage. Conversely, he says, fixed-combination vitamin D-steroid products can increase adherence because there’s only one product to use, and these products’ safety and efficacy have been tested out to one year. Additionally, combinations such as calcipotriene with either halobetasol or betamethasone have data dating back more than a decade.
For years, adds Dr. Pariser, dermatologists have compounded topical steroids with other agents such as salicylic acid or calcineurin inhibitors, as well as other older agents.
Dr. Pariser is a current or previous investigator and/or consultant for AbbVie, Amgen, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Eli Lilly, Janssen, LEO Pharma, Merck, Novartis, Ortho Dermatologics, Pfizer, Promius and Sun Pharma.
David M Pariser MD. “Combination Therapy in Managing Psoriasis Patients.” South Beach Symposium. February 8, 2020.