How the Noristerat Contraceptive Injection Works

The Noristerat injection is a reversible, progestin-only method of prescription birth control that works by preventing ovulation, thickening cervical mucus, and thinning the uterine lining so that an egg is less likely to implant. This contraceptive injection contains the progestin hormone, norethisterone enantate.

The effectiveness, advantages, and disadvantages of Noristerat are similar to Depo Provera but its duration of action is shorter (Noristerat lasts for eight weeks as compared to Depo Provera, which lasts for 12 weeks). Noristerat does not offer any protection against sexually transmitted infections (STIs).

Noristerat is not available in the United States, but it is common in the United Kingdom, Europe, Africa, and Central and Latin America. This article discusses the uses, side effects, and effectiveness of Noristerat.

Doctor holding syringe
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Why Is Noristerat Not Available in the United States?

The Food and Drug Administration (FDA) has long resisted approving Noristerat due to animal studies that suggested it may increase the risk of breast cancer, albeit slightly.

It's important to remember that the FDA had the same concerns about Depo-Provera and denied the approval of that drug several times before its eventual licensing in 2004.

Noristerat is also known as Doryxas, Norethisterone injectable, Norigest, Nur-Isterate, Syngestal, and Unidepo.

Noristerat Uses

Noristerat is a contraceptive that is injected into the muscle of the buttock. The injection is usually given during the first one to five days of your monthly period. Noristerat will continuously release progestin into your bloodstream over a period of eight weeks (two months).

Noristerat is meant to be a short-term method of contraception. After eight weeks, you can only have one more Noristerat injection.

Indications

Noristerat is meant to be a short-term method of contraception. It is mainly used by women under these circumstances:

  • Their partner is having a vasectomy (the Noristerat injection will offer pregnancy protection until the vasectomy becomes effective).
  • They are being immunized against rubella.

Noristerat does not have any estrogen, so this injection may be a good short-term birth control method if you cannot use estrogen-based contraceptives. It is also a contraceptive option if you are breastfeeding.

How Noristerat Works

The norethisterone protects against pregnancy in three key ways:

  • Prevents ovulation: Norethisterone prevents the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH), two hormones that are responsible for stimulating ovulation.
  • Thickens cervical mucus: Norethisterone contains a hormone called norethindrone that thickens the fluid in your cervix to prevent sperm from entering.
  • Thins the uterine lining: Norethisterone thins and stabilizes the uterine lining, preventing eggs from implanting.

Noristerat vs. Depo-Provera

Noristerat and Depo-Provera are both long-acting, progesterone-only, injectable contraceptives. Of the two, Depo-Provera is the longer acting, providing 12 weeks of protection from pregnancy compared to eight weeks for Noristerat.

After the Injection

For the eight weeks that you are using Noristerat, it is important for you to check your breasts and nipples once a month for any changes (such as dimpling of the skin or lumps). If you need to have blood work done, make sure that your healthcare provider knows that you are using Noristerat. This is because Noristerat may affect some of your results.

Your healthcare provider also needs to be aware that you have had the Noristerat injection if you are going to undergo any surgery during the eight-week time frame. Keep in mind that once you stop taking Noristerat, it can take up to a month longer (than other hormonal methods) for you to start ovulating again and regain your fertility.

Side Effects of Noristerat

Not every person will have side effects from this injection. The most commonly reported Noristerat side effects are:

  • Spotting or breakthrough bleeding
  • Delayed period
  • Irregular or heavier bleeding
  • Weight gain
  • Headaches
  • Dizziness and/or nausea
  • Skin reactions (such as pain, rash and/or itch at the injection site

Contraindications

Noristerat should not be used by people with:

  • Known or suspected pregnancy
  • A known risk or history of blood clots
  • A history of arterial or cardiovascular disease, such as heart attack or atherosclerosis
  • High blood pressure
  • High cholesterol
  • Severe liver disease or liver tumor
  • Known or suspected cancer of the breast or genital organs
  • Diabetes mellitus
  • Undiagnosed vaginal bleeding

If you have one of these conditions or suspect you might, talk to your healthcare provider about whether Noristerat is right for you.

Effectiveness of Noristerat

Noristerat is 97% to 99.7% effective. This means that with typical use, 2 out of every 100 people who use Noristerat become pregnant in one year. With perfect use, less than 1 out of every 100 people who use Noristerat will become pregnant in one year.

If you receive the Noristerat injection during the first five days of your period, then it is effective immediately and no back-up birth control is needed. There are certain medications that can lower the effectiveness of Noristerat.

Summary

Noristerat is an injectable type of birth control that is not available in the United States. It's common in the United Kingdom, Europe, Africa, and Central and Latin America. Noristerat only contains the hormone progestin. The FDA hasn't approved Noristerat due to animal studies and it may increase the risk of breast cancer. Noristerat lasts for eight weeks and does not protect against STIs. Side effects may include spotting, irregular or heavier bleeding, weight gain, headaches, skin reactions, and more.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Patient. Norethisterone contraceptive injection.

  2. World Health Organization. Facts about injectable contraceptives: memorandum from a WHO meeting. Bull WHO. 1982;60(2):199-210.

  3. Kline W. Bodies of evidence: activists, patients, and the FDA regulation of Depo-Provera. J Womens Hist. 2010;22(3):64-87. doi:10.1353/jowh.2010.0588

  4. Datapharm. Noristerat 200mg, solution for intramuscular injection.

  5. NHS. The contraceptive injection.

  6. Benagiano G, Gabelnick H, Brosens I. Long-acting hormonal contraception. Womens Health (Lond). 2015 Nov;11(6):749-57. doi:10.2217/whe.15.68

  7. Noory A, Aboud HK, Essam N, Hashemi AR. The side effect of noristerat injection in some biochemistry parameters in Al-Diwaniya City. Pak J Biotechnol. 2018;15:(3)699-702.

  8. Patient. Norethisterone contraceptive injection.

  9. Bayer. Noristerat.

By Dawn Stacey, PhD, LMHC
Dawn Stacey, PhD, LMHC, is a published author, college professor, and mental health consultant with over 15 years of counseling experience.