Transdermal cream bases--a study of absorption

[Guest guest]

I'm now back working at a compounding pharmacy (doing marketing of

compounds), and I've discovered that PCCA (Pharmaceutical Compounding

Centers of America, which supplies a lot of compounders with their

chemicals and bases) did a study of the percutaneous absorption of

progesterone, in vitro, using human cadaver skin abtained within 24-

48 after death. (The actual study was performed by PRACS Institute,

an independent research facility.) The four base creams tested were

VersaBase Cream, Cosmetic HRT, a mixture of VersaBase Cream (95%) and

VersaBase Gel (5%), and Vanicream. (The first three bases are PCCA

bases; Vanicream is from Pharmceutical Specialties, Inc.) The

progesterone was Progesterone USP, PCCA Special Micronized, 50 mg/gm.

The creams were tested on replicate sections from three different

cadaver skin donors for absorption over a 48-hour period. The skin

was mounted in specially designed diffusion cells that allowed it to

be maintained at a temperature and humidity to match typical in vivo

conditions. The progesterone was not rubbed into the skin but applied

with a pipette and left to diffuse.

Results: all the bases demonstrated the ability to transport

progesterone across human skin in vitro. When comparing the bases'

ability to transport progesterone deep into the dermis, PCCA

VersaBase Cream out-performed all bases, delivering more than four

times as much progesterone as VaniCream. Looking at the graph

included in the study, the other two bases delivered a little less

than half of the amount delivered by VersaBase. Absorption was

observed to rise to a peak at approximately seven hours after

application followed by a slow decline in flux over time and what the

study called a " transient secondary peak " of penetration at

approximately 28 hours after application at about half the flux seen

at the maximum.

My pharmacy is switching to VersaBase, so I guess I'll be paying some

attention to whether my hormone dosages need to be lowered in the

near future. Others using transdermal creams may want to check with

their pharmacist to see what base he/she uses. It could be a reason

why some experience good results with transdermal creams and others

do not.

Virginia