title: Pharmacokinetics of levonorgestrel in the rat.
abstract: Levonorgestrel was administered intravenously as a bolus to adult female rats and blood samples were collected at various time intervals. Serum concentrations of levonorgestrel were measured by radioimmunoassay. Analysis of data for two- and three-compartment open models indicated that in the rat, as in the human and the rabbit, a tri-exponential equation provided a better fit of the data. The half-lives for the alpha, beta and gamma phases were 10.1 min, 42.7 min and 23.1 hours, respectively. These values were closer to those reported for women than were the half-lives reported for the rabbit. The alpha and the beta phases appeared to last for 51 min and 1.3 hours, respectively, and the gamma phase was longer than 45 hours.
mesh_terms: D000818:Animals; D003277:Contraceptives, Oral, Combined / Q000097:blood; D003429:Cross Reactions; D006207:Half-Life; D006801:Humans; D007106:Immune Sera; D007700:Kinetics; D016912:Levonorgestrel; D008954:Models, Biological; D009644:Norgestrel / Q000097:blood*; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D013237:Stereoisomerism
chemical_list: D003277:Contraceptives, Oral, Combined; D007106:Immune Sera; D009644:Norgestrel; D016912:Levonorgestrel