The injectable contraceptives depot medroxyprogesterone acetate (DMPA) and norethisterone enanthate (NET-EN) each contain a progestin like the natural hormone progesterone in a woman’s body.

(In contrast, monthly injectables contain both estrogen and progestin. See Monthly Injectables).

Do not contain estrogen, and so can be used throughout breastfeeding and by women who cannot use methods with estrogen.

DMPA, the most widely used progestin-only injectable, is also known as “the shot,” “the jab,” the injection, Depo, Depo-Provera, Megestron, and Petogen.

NET-EN is also known as norethindrone enanthate, Noristerat, and Syngestal. (See comparing injectables, for differences between DMPA and NET-EN.)

Given by injection into the muscle (intramuscular injection). The hormone is then released slowly into the bloodstream. A different formulation of DMPA can be injected just under the skin (subcutaneous injection). See New formulation of DMPA, further down on this page.

Work primarily by preventing the release of eggs from the ovaries (ovulation).

Effectiveness depends on getting injections regularly: risk of pregnancy is greatest when a woman misses an injection.

As commonly used, about 3 pregnancies per 100 women using progestin-only injectables over the first year. This means that 97 of every 100 women using injectables will not become pregnant.

When women have injections on time, less than 1 pregnancy per 100 women using progestin-only injectables over the first year (3 per 1,000 women).

Return of fertility after injections are stopped: An average of about 4 months longer for DMPA and 1 month longer for NET-EN than with most other methods (see Question 7).

Protection against sexually transmitted infections (STIs): none

Some users report the following:

Changes in bleeding patterns including, with DMPA:

First 3 months:

– Irregular bleeding

– Prolonged bleeding

At one year:

– No monthly bleeding

– Infrequent bleeding

– Irregular bleeding

NET-EN affects bleeding patterns less than DMPA. NET-EN users have fewer days of bleeding in the first 6 months and are less likely to have no monthly bleeding after one year than DMPA users.

• Weight gain (see Question 4)
• Headaches
• Dizziness
• Abdominal bloating and discomfort
• Mood changes
• Less sex drive
• Other possible physical changes:

Loss of bone density (see Question 10)

Why Some Women Say They Like Progestin-Only Injectables

Progestin-only injectables:

• Can stop monthly bleeding, but this is not harmful. It is similar to not having monthly bleeding during pregnancy. Blood is not building up inside the woman.
• Do not disrupt an existing pregnancy.
• Do not make women infertile.

A formulation of DMPA has been developed specifically for injection into the tissue just under the skin (subcutaneously).

This new formulation must be delivered by subcutaneous injection.

It will not be completely effective if injected in other ways. (Likewise, DMPA for injection into the muscle must not be injected subcutaneously.)

The hormonal dose of the new subcutaneous formulation (DMPA-SC) is 30% less than for DMPA formulated for injection into the muscle—104 mg instead of 150 mg. Thus, it may cause fewer side effects, such as weight gain.

Contraceptive effectiveness is similar. Like users of intramuscular DMPA, users of DMPA-SC have an injection every 3 months.

DMPA-SC will be available in prefilled syringes, including the single-use Uniject system. These prefilled syringes will have special short needles meant for subcutaneous injection.

With these syringes, women could inject DMPA themselves.

DMPA-SC was approved by the United States Food and Drug Administration in December 2004 under the name “depo-subQ provera 104.” It has since also been approved in the United Kingdom.

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