Author(s): Limpongsanurak S, Jenkins N, Fotherby K
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Abstract Serum sex hormone binding globulin and caeruloplasmin levels were measured in women receiving 30 microgram or 50 microgram ethinyl oestradiol daily or a 'triphasic' formulation containing ethinyl oestradiol and levonorgestrel. In women taking ethinyl oestradiol alone, there was a rapid increase in the levels of both proteins, and even 10 days after the last tablet the levels were still elevated. There was no significant difference between the serum levels of the proteins in women receiving the two doses of ethinyl oestradiol, but the percentage change was significantly higher in the 50 microgram group than in the 30 microgram group. In women using the 'triphasic' formulation, levels of the proteins were significantly lower than in women taking ethinyl oestradiol alone. There was a marked variation between women in the changes produced. This marked inter-subject variation may be important in the development of side-effects in women using steroidal contraceptives. PIP: Clinical research was conducted with human volunteers to ascertain the effect on serum levels of 2 proteins of hepatic origin--SHBG (sex hormone binding globulin) and CP (caeruloplasmin)--of 30 mcg and 50 mcg ethinyl estradiol administered alone and the new "triphasic" formulation consisting of low doses of ethinyl estradiol and levonorgestrel. Ethinyl estradiol caused a rapid increase in the mean levels of both SHBG and CP, which showed up as early as 2-3 days after initiation of the therapy and continued beyond the time of the therapy. Even the lower dose of ethinyl estradiol caused elevation of the 2 protein levels. Even the low dose of levonorgestrel present in the "triphasic" regimen had a sufficient antiestrogenic effect to prevent marked increase in both SHBG and CP. There were no significant differences in serum levels of the proteins in the women receiving the 30 mcg or the 50 mcg dosages. However, in any individual woman, the changes occurring with 30 mcg would be less than those occurring with 50 mcg. The study showed that there are marked inter-subject variations in metabolic changes occurring as a result of exposure to steroidal contraceptives.
This article was published in Curr Med Res Opin
and referenced in Journal of Bioequivalence & Bioavailability