This might have been due to additional ethinylestradiol generated by higher doses of norethisterone. Overdose
There have been no reports of serious side effects with overdose of norethisterone, even in small children. As such, overdose usually does not require treatment. High dosages of as much as 60 mg/day norethisterone have been studied for extended treatment durations without serious adverse effects described. Interactions
5α-Reductase plays an important role in the metabolism of norethisterone, and 5α-reductase inhibitors such as finasteride and dutasteride can inhibit its metabolism. Norethisterone is partially metabolized via hydroxylation by CYP3A4, and inhibitors and inducers of CYP3A4 can significantly alter circulating levels of norethisterone. For instance, the CYP3A4 inducers rifampicin and bosentan have been found to decrease norethisterone exposure by 42% and 23%, respectively, and the CYP3A4 inducers carbamazepine and St. Johns wort have also been found to accelerate norethisterone clearance. Pharmacology
Pharmacodynamics
Norethisterone is a potent progestogen and a weak androgen and estrogen. That is, it is a potent agonist of the progesterone receptor (PR) and a weak agonist of the androgen receptor (AR) and the estrogen receptor (ER). Norethisterone itself has insignificant affinity for the ER; its estrogenic activity is from an active metabolite that is formed in very small amounts, ethinylestradiol (EE), which is a very potent estrogen. Norethisterone and its metabolites have negligible affinity for the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) and hence have no glucocorticoid, antiglucocorticoid, mineralocorticoid, or antimineralocorticoid activity. Progestogenic activity
Norethisterone is a potent progestogen and binds to the PR with approximately 150% of the affinity of progesterone.
In 1964, additional contraceptive preparations containing norethisterone in combination with mestranol or EE, such as Norlestrin and Norinyl, were marketed in the United States. Society and culture
Generic names
Norethisterone is the INN and BAN of the drug while norethindrone is its USAN. Brand names
Norethisterone (NET), including as NETA and NETE, has been marketed under many brand names throughout the world. Availability
United States
Norethisterone was previously available alone in 5 mg tablets under the brand names Norlutin in the United States, but this formulation has since been discontinued in this country. However, NETA remains available alone in 5 mg tablets under the brand name Aygestin in the United States. It is one of the only non-contraceptive progestogen-only drug formulations that remains available in the United States. The others include progesterone, medroxyprogesterone acetate, megestrol acetate, and hydroxyprogesterone caproate, as well as the atypical agent danazol.Both norethisterone and NETA are also available in the United States as contraceptives. Norethisterone is available both alone (brand names Camila, Errin, Heather, Micronor, Nor-QD, others) and in combination with EE (Norinyl, Ortho-Novum, others) or mestranol (Norinyl, Ortho-Novum, others), while NETA is available only in combination with EE (Norlestrin, others). NETE is not available in the United States in any form. Research
Norethisterone, as NETA and NETE, has been studied for use as a potential male hormonal contraceptive in combination with testosterone in men.Long-acting norethisterone microspheres for intramuscular injection have been studied for potential use in birth control. References
Further reading
External links
"Norethindrone". Drug Information Portal. U.S. National Library of Medicine.