Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures and partial seizures, but not absence seizures. The intravenous form is used for status epilepticus that does not improve with benzodiazepines. It may also be used for certain heart arrhythmias or neuropathic pain. It can be taken intravenously or by mouth. The intravenous form generally begins working within 30 minutes and is effective for 24 hours. Blood levels can be measured to determine the proper dose.Common side effects include nausea, stomach pain, loss of appetite, poor coordination, increased hair growth, and enlargement of the gums. Potentially serious side effects include sleepiness, self harm, liver problems, bone marrow suppression, low blood pressure, and toxic epidermal necrolysis. There is evidence that use during pregnancy results in abnormalities in the baby. It appears to be safe to use when breastfeeding. Alcohol may interfere with the medication's effects.Phenytoin was first made in 1908 by the German chemist Heinrich Biltz and found useful for seizures in 1936. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Phenytoin is available as a generic medication and usually not too expensive. The wholesale cost in the developing world is between US$0.003 and US$0.15 per dose. A month of treatment is about US$30 in the United States.