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. Johns 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).
Aquatic tetrapods
In many secondarily aquatic vertebrates, the non-bony tissues of the forelimbs and/or hindlimbs are fused into a single flipper. Some remnant of each digit generally remains under the soft tissue of the flipper, though digit reduction gradually occurs such as in baleen whales (mysticeti). Marine mammals evolving flippers represents a classic example of convergent evolution, and by some analyses, parallel evolution.Full webbing of the digits in the manus and/or pes is present in a number of aquatic tetrapods. Such animals include marine mammals (cetaceans, sirenians, and pinnipeds), marine reptiles (modern sea turtles and extinct ichthyosaurs, mosasaurs, plesiosaurs, metriorhynchids), and flightless aquatic birds such as penguins. Hyperphalangy, or an increase in the number of phalanges beyond ancestral mammal and reptile conditions, is present in modern cetaceans and extinct marine reptiles. Schizodactyly
Schizodactyly is a primate term for grasping and clinging with the second and third digit, instead of the thumb and second digit. See also
Artiodactyl – even-toed ungulates, clade Cetartiodactyla
Perissodactyl – odd-toed ungulates

References
External links
Coates, Michael (25 April 2005). "Why do most species have five digits on their hands and feet?". Scientific American. Retrieved 2009-07-05.