Plasma equilin concentrations in an oophorectomized woman following ingestion of conjugated equine oestrogens (Premarin).

The plasma equilin concentration was 25.2 nmol/l (6.7 ng/ml) 4 h after an oral dose of Premarin (1.25 mg), and a maximum concentration of 20.5 nmol/l (5.5 ng/ml) was recorded 3 h after a smaller dose (0.625 mg) was given. 24 h later, the plasma equilin was still considerable, being 6.1 nmol/l (1.6 ng/ml) and 3.7 nmol/l (1.2 ng/ml) for the larger and smaller dosages respectively. The findings for equilin are considerably higher than physiological oestrogen concentrations and in addition show that daily therapy with Premarin could lead to cumulation of the steroid.