A contraceptive patch contains the same hormones as a contraceptive pill, but in lower levels, as these hormones enter the body trough the skin. It effectiveness, proven by trials, is 99 %.

A patch is square shaped, with a 3.6 cm (1.3 inch) side and has 3 layers. The hormones are in the middle layer, being freed progressively when the patch is applied on the skin.

The patch releases daily 20 micrograms of a progestagen (named norelgestromin) and 15 micrograms of an estrogen (ethinylestradiol), which once they reach the brain, action on the hypophysis, inhibiting the release of hormones responsible with the ovulation. It can be placed indiscriminately over the abdomen, buttocks or every body part, except breasts. Every week, the patch must be removed and replaced by another one, in other part of the body than the previous one.

After placing the third patch, a resting period follows, to let the menstruation pass. Thus, the hormonal therapy lasts 21 days followed by a 7 days interruption. The contraceptive pills require higher doses of hormones, as they have to pass first through the digestive tube, while the patches, as they administer the hormones directly to the bloodstream through the skin, employ much lower amounts.

Another advantage is that the patch does not lose efficacy in case of diarrhea or vomiting. In change, it can detach under the shower or while swimming in the sea or a pool. However, the clinical trials showed it does not fall easily. But the patch inflicts some secondary effects observed on pills, like nauseas, blood clotting, liquid retention, cardiovascular impairments and apoplexy.

The patch also must not be used by smoking women older than 35, those suffering from cardiovascular conditions and those suffering from obesity (over 90 kg or 405 pounds). In some women, the contraceptive patch can also induce skin irritations.