Release of 19-nor-testosterone type of contraceptive steroids through different drug delivery systems into serum and breast milk of lactating women

Contraception. 1980 Mar;21(3):217-23. doi: 10.1016/0010-7824(80)90002-5.


The release of contraceptive steroids through different drug delivery systems into serum and breast milk was investigated in a group of lactating women. Four women in each group were taking either a low dosage progestogen compound like norethisterone (NET) 350 micrograms or d-norgestrel (d-Ng) 50 micrograms alone or low dosage combination pills containing NET 1 mg or d-Ng 150 micrograms with 30 micrograms ethinyl estradiol (EE2) or a biodegradable implant containing 25 mg NET or d-Ng. Peak levels in plasma and milk were seen in oral contraceptive users around 2 hours. Of the two low dosage progestogen compounds, d-Ng was below the detection limit in milk within 4 hours whereas NET was still detectable at the 24-hour interval. In contrast to this, because of the larger quantity of steroids in the combination pills, the NET/d-Ng levels in serum as well as in milk were high throughout the 24-hour period. With the subdermal route because of the sustained low release of the drug from the biodegradable implants, the levels in milk were below the detection limit within a day with d-Ng and within a week with NET.

PIP: Various drug delivery systems were tested and the release rates of steroids were measured in the serum and breast milk of a group of lactating women. 24 lactating women were divided into 3 groups: 1) low-dose combination (LDC) oral pill group; 2) low-dose progestin-only (LDP) oral pill group; and 3) biodegradable-cholesterol implants. Norethindrone (NET) or D-norgestrel (D-Ng) was the steroid released and it was assayed. LDC contained either 1 mg of NET or 150 mcg of D-Ng; LDP was 350 mcg of NET or 50 mcg of D-Ng; and the implants contained 25 mg of D-Ng or NET. By the oral route, peak levels of steroid were observed in both plasma and milk about 2 hours postdosing. In the LDP formulations, NET persisted within limits of detection for over 24 hours, whereas D-Ng was below the limit of detection in milk after 4 hours. In the LDC, however, detectable levels of both NET an D-Ng persisted for 24 hours. In the group implanted subcutaneously with progestin, levels of D-Ng were undetectable in milk within 1 day of insertion, and those of NET were undetectable within 1 week of implantation.

MeSH terms

  • Drug Implants
  • Ethinyl Estradiol / blood
  • Ethinyl Estradiol / metabolism*
  • Female
  • Humans
  • Milk, Human / analysis*
  • Norethindrone / administration & dosage
  • Norethindrone / blood
  • Norethindrone / metabolism*
  • Norgestrel / administration & dosage
  • Norgestrel / blood
  • Norgestrel / metabolism*


  • Drug Implants
  • Norgestrel
  • Ethinyl Estradiol
  • Norethindrone