NorgestrelNorgestrel is a progestin which is used in birth control pills sold under the brand name Ovral in combination with the estrogen ethinylestradiol and Opill by itself. It is also used in menopausal hormone therapy. It is taken by mouth. Side effects of norgestrel include menstrual irregularities, headaches, nausea, and breast tenderness. The most common side effects of the progestin-only Opill include irregular bleeding, headaches, dizziness, nausea, increased appetite, abdominal pain, cramps, or bloating.