Milk and plasma concentrations of the progestin ST-1435 in women treated parenterally with ST-1435.
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.
Lähteenmäki
P L
PL
Department of Medical Chemistry, University of Helsinki, Finland.
Diaz
S
S
Miranda
P
P
Croxatto
H
H
Lähteenmäki
P
P
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
D003271:Contraceptive Agents, Female; D004343:Drug Implants; D009653:Norprogesterones; C029167:ST 1435