Isotretinoin is a medication which is used for the treatment varying levels of acne. This drug was initially developed for chemotherapy to treat various forms of cancer. Its ability to kill rapidly dividing cells still makes it a viable option for the treatment of cancer. Oral isotretinoin is advertised under various brand names, most commonly Accutane, but there are many pharmaceutical companies who manufacture this drug.

Isotretinoin is a fat-soluble vitamin (vitamin A) and was an early treatment of acne which was initially used during the 1930s. At high doseage levels, there is Vitamin A toxicity. Using animal-based vitamin A taken over the course of a year has also been shown to significantly reduce acne. Since vitamin A is good for the skin and is known to reduce sebum production at extremely high dosages, isotretinoin with a retinoic acid derivative (originally developed by Hoffmann-La Roche) was a synthetic compound and had an overall better success with acne treatment.

Isotretinoin has been known to have the potential to disturb the growth and development of an embryo or fetus, so pregnancies while on the drug are discouraged. When pregnancies on the drug do occurr, they have been found to have high rates of inborn malformation. In the late 1990s, the drug came under scrutiny, as less than half of the drug's prescribers were testing for pregnancy using anything other than unreliable urine testing. The FDA soon instituted restrictions on prescribing the drug, first with the SMART system in 2000, and then in 2006, the iPLEDGE program.

In early 2002, Roche Pharmaceuticals' patents for the drug expired and now there are many other companies selling generic versions all over the world. In 2009, Roche Pharmaceuticals discontinued the manufacture and distribution of the Accutane brand in the US. Generic versions of isotretinoin are available online from countries where it can be dispensed without a prescription.

Oral isotretinoin is best absorbed when taken after a meal which is high in fat, as the drug has a high lipophilicity. After oral administration, at least three metabolites have been detected in human plasma. These are 4-oxo-retinoic acid, 4-oxo-isotretinoin, and retinoic acid. Isotretinoin also irreversibly oxidizes to 4-oxo-isotretinoin. The metabolites of isotretinoin are excreted through urine and feces and the mean elimination half-life is about 21 hours, with a standard deviation of about 8 hours.

Usually, treatment of acne begins with topical medications followed by oral antibiotics and lastly isotretinoin therapy. This is because while less effective than isotretinoin, other treatments are thought to be associated with a lower cost as well as fewer undesired side effects. The higher cost of isotretinoin is partially due to the medical supervision required in the cases of toxic dosages as well as the the cost of the medicine itself.

The dose of isotretinoin a patient should receive depends on the severity of their condition as well as their weight. As an initial course of treatment, high doses are administered for 4 to 6 months. A second course of treatment may be used two months following the cessation of the initial course of treatment if severe acne returns. Efficiency seems to be related to the cumulative dose of isotretinoin taken. Some studies show that lower dosage treatments are just as effective with diminished or unapparent side effects, whereasincreasingly higher dosages will result in higher toxicity, which resembles vitamin A toxicity.

Common side effects include mild acne flare, dryness of the skin, lips and mucous membranes, infection of the cuticles, skin peeling, cheilitis, itch, hyperlipidaemia, rosacea, rash, reduced tolerance to contact lenses, skin fragility, flushing, dry eyes, permanent thin skin, nose bleeds, eye irritation, diffuse alopecia areata, conjunctivitis, raised liver enzymes, headaches, back pain, and permanent hair thinning, myalgia and/or arthralgia.

Uncommon side effects include severe acne flare, increased erythrocyte sedimentation rate, raised blood glucose level, and fatigue.

Rare side effects include inpaired night vision, corneal opacities, cataracts, skeletal hyperostosis, inflammatory bowel disease, optic neuritis, papilloedema, menstrual disturbances, pancreatitis, hepatitis, extraosseous calcification, idiopathic intracranial hypertension, and psychosis.