title: Milk and plasma concentrations of the progestin ST-1435 in women treated parenterally with ST-1435.
abstract: A subcutaneous contraceptive capsule releasing progestin ST-1435 was used by 6 breast-feeding women. One to three paired milk and plasma samples were collected over a one-month period and the concentrations of ST-1435 were determined by radioimmunoassay. An improved and sensitive method for determination of ST-1435 in milk was developed. A column chromatographic purification of milk prior to radioimmunoassay decreased the blank and improved sensitivity. The average plasma concentration of ST-1435 was 62 +/- 20 pg/ml (mean +/- SD). The average milk concentration of ST-1435 was 38 pg/ml (ranging from 7 to 73 pg/ml), while the average milk to plasma ratio was 0.60 (ranging from 0.25 to 0.91). There was a significant correlation between ST-1435 concentrations in breast milk and plasma, indicating that the concentration in plasma is the major determinant for the amount of ST-1435 excreted into milk. Since studies with this drug have shown good contraceptive efficacy and low bioavailability after oral intake, ST-1435 is a good candidate for lactational contraception.
authors: Department of Medical Chemistry, University of Helsinki, Finland.
authors: P L
authors: PL
authors: Lähteenmäki
authors: S
authors: S
authors: Diaz
authors: P
authors: P
authors: Miranda
authors: H
authors: H
authors: Croxatto
authors: P
authors: P
authors: Lähteenmäki
mesh_terms: D003271:Contraceptive Agents, Female / Q000493:pharmacokinetics*; D004343:Drug Implants; D005260:Female; D006801:Humans; D007774:Lactation / Q000378:metabolism*; D008895:Milk, Human / Q000737:chemistry*; D009653:Norprogesterones / Q000097:blood / Q000378:metabolism*; D011863:Radioimmunoassay
chemical_list: D003271:Contraceptive Agents, Female; D004343:Drug Implants; D009653:Norprogesterones; C029167:ST 1435