Q:I am compounding a preparation intended toadminister testosterone and dehydroepiandrosteronetransdermally, but the gel keeps "breaking."Iam using a carbomer/alcohol/water gel that is preserved anda small amount of ethanol as the levigating agent.
A:Compounding hormones and/or other active ingredientsinto gel basis for transdermal administration isa widely accepted pharmaceutical practice and iswell-documented in the literature. Clinical observation andmonitoring of appropriate markers during this therapy can bebeneficial to the patient—the goal of extemporaneously compoundedtherapy is individual outcome. A key component oftransdermal gels is of a penetration enhancer such as isopropylpalmitate/lecithin (50/50 w/w; Lipoil). In this combination,phospholipids/micelles are liberated from the solubilizedlecithin. Phospholipids are well-known to aid the transport ofactive ingredients into the skin for absorption. The penetrationenhancer usually is incorporated as 22% to 24% of the formulationand probably should be included here.
As to the "broken"gel, carbomer gels are pH-sensitive andalso can break when overloaded with ingredients. Literaturereferences point to the use of a poloxamer gel at 20% to 30%concentration in water (Pluronic F127 NF or Polox), a clearsolution at refrigerated temperatures that becomes a semisolidat room-to-body temperatures. This behavior allows thematerial to remain in place where applied to the skin, insteadof running off as a carbomer or methylcellulose gel might.
Mr. Erickson is director of professional affairs at Gallipot Inc.