effects of desogestrel may include menstrual irregularities, amenorrhea, headaches, nausea, breast tenderness, and mood changes (e.g., depression), as well as weight gain, acne, and hirsutism. However, it has also been reported to not adversely affect weight. In addition, acne and hirsutism are negligible when combined with ethinylestradiol, and this combination can actually be used to treat such symptoms. Desogestrel can also cause changes in total, , and cholesterol. Uncommon side effects of desogestrel may include vaginal infection, contact lens intolerance, vomiting, hair loss, dysmenorrhea, ovarian cysts, and fatigue, while rare side effects include rash, urticaria, and erythema nodosum. Breast discharge, ectopic pregnancies, and aggravation of angioedema may also occur with desogestrel. Serious side effects of combined oral contraceptives containing desogestrel may include venous thromboembolism, arterial thromboembolism, hormone-dependent tumors (e.g., liver tumors, breast cancer), and melasma. Overdose No serious harmful effects have been reported with overdose of desogestrel. Symptoms may include nausea, vomiting, and, in young girls, slight vaginal bleeding. In safety studies, dosages of up to 750 μg/day desogestrel in women showed no adverse effects on laboratory and various other parameters and produced no reported subjective side effects. There is no antidote to desogestrel overdose and treatment should be based on symptoms. Interactions Inducers of liver enzymes can increase the metabolism of desogestrel and etonogestrel and reduce their circulating levels. This may result in contraceptive failure. Examples of liver enzyme inducers include barbiturates (e.g., phenobarbital), bosentan, carbamazepine, efavirenz, phenytoin, primidone, rifampicin, and possibly also felbamate, griseofulvin, oxcarbazepine, rifabutin, St. John's Wort, and topiramate. Many antivirals for HIV/AIDS and HCV, such as boceprevir, nelfinavir, nevirapine, ritonavir, and telaprevir, may increase or decrease levels of desogestrel and etonogestrel. CYP3A4 inhibitors including strong inhibitors like clarithromycin, itraconazole, and ketoconazole and moderate inhibitors like diltiazem, erythromycin, and fluconazole may increase levels of desogestrel and etonogestrel. Hormonal contraceptives may interfere with the metabolism of other drugs, resulting in increased levels (e.g., ciclosporine) or decreased levels (e.g., lamotrigine). Pharmacology Pharmacodynamics Desogestrel is a prodrug of etonogestrel (3-ketodesogestrel), and, via this active metabolite, it has progestogenic activity, antigonadotropic effects, very weak androgenic activity, very weak glucocorticoid activity, and no other hormonal activity. Progestogenic activity Desogestrel is a progestogen, or an agonist of the progesterone receptor (PR). It is an inactive prodrug of etonogestrel with essentially no affinity for the PR itself (about 1% of that of promegestone). Hence, etonogestrel is exclusively responsible for the effects of desogestrel.