A Radioimmunoassay for Norethindrone. II. Plasma Levels in Hypertensive and Nomotensive Oral Contraceptive Users

Abstract
A sensitive radioimmunoassay for measurement of norethindrone (N) in blood plasma has been developed. The coefficient of variation within the assay and between assays was 7 and 13.5% respectively. The procedural blanks were negligible, and recovery was approximately 81.8%. Blood plasma levels of N in 20 normotensive and 6 hypertensive women who were ingesting oral contraceptives (OCs) were measured, and the results indicate that the subjects who became hypertensive while taking OCs had significantly higher levels of N compared with normotensive OC users (p < .001).