Last update April 28, 2026

G03AA05

Likely Compatibility

Fairly safe. Mild or unlikely adverse effects. Compatible under certain circumstances. Follow-up recommended. Read Commentary.

Combined oral contraceptive (COC) of estrogen (ethinyl estradiol) and progestogen (norethisterone or norethindrone) in the form of pills for oral use. Daily administration.

For a detailed discussion with references:

  • on why non-hormonal methods are the first choice during the first 4–6 weeks postpartum, followed by IUDs and progestin implants,
  • on the potential problems associated with the use of combined estrogen-progestin contraceptives,
  • the possible decrease in milk production with estrogen use,
  • and why progestin-only contraceptives are preferable during breastfeeding,

see below: “(Combined Estrogen + Progestin Contraceptives, COCs)”

ETHINYLESTRADIOL is a synthetic estrogen that has a similar action as estradiol. 

Its pharmacokinetic data (high percentage of protein binding and very wide volume of distribution) explain the negligible or null passage into breast milk observed. (Segev 2025, Betrabet 1986, Nilsson 1978)

NORETHISTERONE (norethindrone) is a progestin derivative of 19-nortestosterone. 

Norethindrone and progestins in general are considered the contraceptives of choice during breastfeeding because they are not significantly excreted in breast milk, do not alter the quantity or composition of breast milk, do not cause side effects, and do not affect the growth and development of infants or the duration of breastfeeding. These details, along with references, can be found below under “Norethisterone”

American Academy of Paediatrics: COCs are usually compatible with breastfeeding. (AAP 2001)


See below the information of these related products:

Alternatives

Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.

Jose Maria Paricio, Founder & President of APILAM/e-Lactancia

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Other names

G03AA05 is Ethinylestradiol + Norethisterone in ATC Code/s.

Is written in other languages:

Groups

G03AA05 belongs to these groups or families:

Tradenames

Main tradenames from several countries containing G03AA05 in its composition:

Pharmacokinetics

Variable Value Unit
Oral Bioavail. 40-60 / 64 %
Molecular weight 296 / 298 daltons
Protein Binding 99 / 99 %
VD 5 - 10 / 4 l/Kg
pKa 10.3 / 17.6 -
Tmax 1.5 ± 0.5 / 1 - 2 hours
T½ 8 ± 5 / 8 -10 hours
M/P ratio 0.3 / 0.3 -
Theoretical Dose < 0.000045 / < 0.0004 mg/Kg/d
Relative Dose < 0.54 / < 1.9 %

References

  1. Segev L, Ben Zimra A, Weitzman GA, Bloch N, Pitussi I, Alkhazov T, Kogan NM, Peleg D, Samson AO, Ben Shachar I. Ethinylestradiol Transfer into Breast Milk of Women Using Low-Dose Combined Hormonal Contraception Is Negligible. Open Access J Contracept. 2025 Dec 10;16:189-197. Abstract Full text (link to original source)
  2. Betrabet SS, Shikary ZK, Toddywalla VS, Patel D, Vaidya P, Saxena BN. ICMR Task Force Study on hormonal contraception. Biological activity of ethinyl estradiol present in the breast milk. Contraception. 1986 Abstract
  3. Nilsson S, Nygren KG, Johansson ED. Ethinyl estradiol in human milk and plasma after oral administration. Contraception. 1978 Abstract

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