The plasma levels of testosterone (T) were measured after oral administration of 25 mg T and 40 mg testosterone-undecanoate (TU) in a group of young women by a specific radioimmunoassay. Plasma levels were compared to those after intravenous administration of 1.5 micrograms testosterone/kg to another group of young women for determination of absolute bioavailability. Due to the high metabolic clearance rate of 24.5 ml/min/kg absolute systemic availability of free testosterone was calculated to 3.56 +/- 2.45%. Oral administration of testosterone undecanoate leads only to an absolute testosterone bioavailability of 6.83 +/- 3.32%.

Six healthy, elderly volunteers received three topical treatments with Advantan^® lotion containing 0.1% of methylprednisolone aceponate (MPA, CAS 86401-95-8) on intact, inflamed and stripped skin in a consecutive fashion at weekly intervals. The lotion (O/W emulsion) containing ¹⁴C-MPA (specific radioactivity 1.8 MBq/mg MPA) was applied in an area dose of 5 mg lotion/cm² on a marked area of 100 cm² on the back for 24 h. Inflammation was caused by UV-B irradiation at 3 MED 6 h prior to the treatment with the test preparation. Removal of stratum corneum was performed by 20-fold adhesive tape stripping. The concentration of radioactivity was measured in the plasma and in the urine up to 7 days following each treatment. The concentration of radioactivity in the plasma did not exceed the limit of detection of 1.5 ng MPA Eq/ml at any time point. The percutaneous absorption was assessed from the cumulated excretion of radiolabelled substances in the urine corrected for biliary excretion. Less than 0.5% of the dose was percutaneously absorbed through intact skin and through inflamed skin. After removal of the penetration barrier (‘stripping’) the percutaneous absorption increased to 15.4±7.7% of the applied dose.

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Six healthy male volunteers received a single topical treatment with 5 g of an anti-acne cream containing 20% azelaic acid (AzA) onto the face, the chest and the upper back. One week later 1 g of AzA was given orally to the same subjects as aqueous microcrystalline suspension. Following the two treatments the renal excretion of the unchanged compound was measured. Analysis included ether extraction of the urine, derivatization of extract and HPLC with UV detection. After topical application 2.2 +/- 0.7%, and after oral administration 61.2 +/- 8.8% of the dose had been excreted unchanged with the urine. By comparing both amounts, the percutaneous absorption of AzA from the cream was assessed to 3.6% of the dermally applied dose.