Interactions
Some drugs such as antibiotics or drugs for epilepsy can interact with the three-month injection. The effect of the contraceptive can be impaired, so that there is no longer any reliable protection against pregnancy. This can also be caused by taking herbal products such as St. John’s wort.
It is therefore essential to inform any doctor who prescribes a medicine about contraception with the three-month injection. Since not all drugs from the above-mentioned groups interact with each other, the practitioner may prescribe a specific drug that is safe in combination with the three-month injection. Antibiotics can influence the effect of the three-month injection, so that safe protection against pregnancy can no longer be guaranteed.
The antibiotics stimulate certain enzymes in the liver, which lead to an increased breakdown of hormones and thus of the active substance of the three-month injection. However, this only applies to some groups of antibiotics. In individual cases the prescribing doctor can inform you whether the contraceptive’s effect is guaranteed. In the case of an infection requiring treatment with antibiotics, a lower level of protection against pregnancy must be accepted in cases of doubt. It is then advisable to use additional condoms.
Contraindications
There are some circumstances in which a three-month injection should never be given. These include bleeding from the vagina, the cause of which has not been clearly determined, as well as existing or past venous thrombosis. This is a blood clot that usually forms in a leg vein and can lead to a life-threatening pulmonary embolism (blockage of a pulmonary vessel by a blood clot). Other contraindications are serious diseases of the liver, cancers of the breast or uterus, certain metabolic diseases and osteoporosis (loss of bone substance). Furthermore, an allergy to components of the contraceptive precludes its use.
Dosage
The principle of the three-month injection is that a depot of the hormone medroxyprogesterone acetate from the group of gestagens is injected into the muscles and from there is released into the blood continuously over the following three months. This requires a relatively high dosage, which is, for example, significantly higher than that of anti-baby pills with a similar active ingredient. This is why side effects of hormone treatment are more frequent and usually more pronounced.
