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Contraception - Management
What are the advantages, disadvantages, and risks of progestogen-only injectables?

  • Advantages:
    • Very effective: when given at the recommended intervals, less than 2 in 1000 women will become pregnant with each year's use:
      • Depot medroxyprogesterone acetate (Depo-Provera®) is more effective than norethisterone enantate (Noristerat®).
    • Users do not have to think about contraception for as long as the injection lasts — 12 weeks for depot medroxyprogesterone acetate and 8 weeks for norethisterone enantate.
    • Sex need not be interrupted to use contraception.
    • Can be used when breastfeeding.
    • Not affected by other medicines.
    • May reduce heavy painful periods and help with premenstrual symptoms.
    • Can be used in situations where combined oral contraceptives are not recommended, such as:
      • Migraine without aura, past history of migraine with aura.
      • Concomitant use of antibiotics/drugs/herbal preparations that induce liver enzymes.
    • Can be used by women with a body mass index greater than 35 kg/m2.
    • May reduce the frequency of seizures in women with epilepsy.
    • May reduce the risk of endometrial cancer.
  • Disadvantages:
    • Not rapidly reversible. After stopping use of progestogen-only injectables:
      • There could be a delay of up to 1 year in the return of normal fertility.
      • Menstruation can take several months to return to normal.
    • Do not protect against sexually transmitted infections.
  • Risks and possible adverse effects:
    • Altered bleeding:
      • Amenorrhoea is likely during use of progestogen-only injectables. It is more likely with depot medroxyprogesterone acetate than norethisterone enantate, is more likely as time goes by, and is not harmful.
      • The most common reason for discontinuation is an altered bleeding pattern, including persistent bleeding: up to 50% of women stop using depot medroxyprogesterone acetate within 1 year.
      • Prolonged and sometimes heavy bleeding is experienced by less than 10% of users.
      • Irregular bleeding may continue for some months after stopping the injections.
    • Increase in body weight — up to 2–3 kg over 1 year:
      • Not all women put on weight, and some lose weight.
      • Overweight women may be at increased risk of gaining weight.
    • There is no evidence of a causal association between the use of progestogen-only injectable contraceptives and mood change or headache.
    • Loss of bone mineral density with long-term use (more than 1 year):
      • The effect is small and largely recovers when depot medroxyprogesterone acetate is stopped.
      • There is no evidence that depot medroxyprogesterone acetate increases the risk of fracture.
      • Women who wish to continue using depot medroxyprogesterone acetate for longer than 2 years should be supported in their decision making: review their clinical situation and discuss the balance between the benefits and potential risks.
      • Because of the possible effect on bone mineral density, progestogen-only injectables are best avoided by adolescents and women with risk factors for osteoporosis (e.g. age over 40 years, longterm use of systemic corticosteroids). They may be given if other methods are not suitable or acceptable.
      • Women should also be warned that additional drugs such as carbamazepine, phenytoin, primidone and sodium valproate are associated with decreased bone mineral density. Strategies to protect against bone mineral density loss such as diet and exercise should be discussed with at-risk women.
  • Unknown effects:
    • There is no good evidence on possible changes in libido, mood changes, or headache.
    • The risk for breast cancer may be slightly increased, but there is uncertainty about the validity of the data.
    • There is no evidence of congenital malformation to the fetus if pregnancy occurs during use of depot medroxyprogesterone acetate.
Basis for recommendation

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