Bioavailability of oestradiol from the Alora TM (0.1 mg/day) oestradiol matrix transdermal delivery system compared with Estraderm (0.1 mg/day)

Abstract

Summary This open-label, randomised, two-way crossover study compared the steady-state bioavailability of oestradiol administered by way of a new oestradiol matrix transdermal delivery system (Alora TM 0.1 mg/day) with that of Estraderm (0.1 mg/day) in 24 subjects. Serum oestradiol, oestrone and oestrone sulphate concentrations were determined by measurement of blood samples. Mean SD pre-dosing, nonadjusted oestradiol levels for Alora (71.9 27.0 pg/ml) were substantially higher than those for Estraderm (26.7 9.7 pg/ml), while peak oestradiol concentrations were comparable. Consequently, fluctuations in steady-state levels were substantially smaller for Alora than for Estraderm; the fluctuation index values (\[C- C ])/ max min C ) were significantly lower for Alora (0.97 0.23) than av for Estraderm (1.68 0.45). Oestradiol levels remained constant over the dosing interval with Alora but decreased significantly after 48 hours with Estraderm. The bioavailability of oestradiol with Alora was 127 56% that of Estraderm. Oestrone and oestrone sulphate data showed the same qualitative and quantitative differences between the two systems. Both systems were well tolerated. In summary, Alora delivered more oestradiol to the systemic circulation with greater consistency and over a longer time than did Estraderm.