Absorption of an oestrogen-progestogen preparation.

The plasma levels of oestradiol (E2), oestrone (E1), and norethisterone were studied in 6 post-menopausal women over a period of 24 h following the ingestion of a single, combined tablet containing 2 mg 17 beta-oestradiol, 1 mg oestradiol and 1 mg norethisterone acetate. The steroids were all in a nonesterified microcrystalline form. Three different batches of the preparation were used in the study; one was freshly prepared and the other two had been stored for 1 and 2 yr, respectively. The plasma oestradiol concentration increased rapidly, reaching a maximum level within 2 h, and then decreased gradually. After 24 h the basal value had not been regained. Oestrone levels followed approximately the same pattern. The E2-to-E1 ratio was high during the first 30 min after ingestion and then decreased to about 0.5. It remained more or less constant at this value, with a slight increase towards the end of the 24-h period. The norethisterone level rose and fell more rapidly. After about 8 h the level was practically down to zero.