Radioimmunoassay of serum norethisterone oenanthate levels in women after intramuscular administration
Saxena, B.N.; Shrimanker, K.; Fotherby, K.
Journal of Steroid Biochemistry 8(10): 1117-1119
1977
ISSN/ISBN: 0022-4731 PMID: 916668 DOI: 10.1016/0022-4731(77)90283-7Document Number: 434403
A radioimmunoassay is described for measuring norethisterone enanthate [a long-acting contraceptive] directly in samples of plasma after methanol precipitation. The method utilizes an antiserum produced against norethisterone enanthate-3-carboxymethyloxime coupled to bovine serum albumin. The method is highly specific for norethisterone enanthate, the antiserum showing a cross-reaction of only 6% with the dihydrometabolite of norethisterone enanthate and less than 0.01% with norethisterone itself. Norethisterone enanthate was injected i.m. into 3 women. Plasma levels of the steroid ester were from 1000-2500 pg/ml 1 wk after injection decreasing to 100-200 pg/ml over the next 6 wk. The pattern of norethisterone enanthate concentrations in plasma was similar to that of norethisterone itself.