Phenytoin

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 focal 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.In contrast to the earlier accidental discovery of the antiseizure properties of potassium bromide and phenobarbital, phenytoin was the product of a search among nonsedative structural relatives of phenobarbital for agents capable of suppressing electroshock convulsions in laboratory animals. 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 focal 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. In 2016 it was the 201st most prescribed medication in the United States with more than 2 million prescriptions. 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. Its use appears to be safe during breastfeeding. Alcohol may interfere with the medication's effects. Severe low blood pressure and abnormal heart rhythms can be seen with rapid infusion of IV phenytoin. IV infusion should not exceed 50 mg/min in adults or 1–3 mg/kg/min (or 50 mg/min, whichever is slower) in children. Heart monitoring should occur during and after IV infusion. Due to these risks, oral phenytoin should be used if possible. At therapeutic doses, phenytoin may produce nystagmus on lateral gaze. At toxic doses, patients experience vertical nystagmus, double vision, sedation, slurred speech, cerebellar ataxia, and tremor. If phenytoin is stopped abruptly, this may result in increased seizure frequency, including status epilepticus. Phenytoin may accumulate in the cerebral cortex over long periods of time which can cause atrophy of the cerebellum. The degree of atrophy is related to the duration of phenytoin treatment and is not related to dosage of the medication. Phenytoin is known to be a causal factor in the development of peripheral neuropathy. Folate is present in food in a polyglutamate form, which is then converted into monoglutamates by intestinal conjugase to be absorbed by the jejunum. Phenytoin acts by inhibiting this enzyme, thereby causing folate deficiency, and thus megaloblastic anemia.Other side effects may include: agranulocytosis, aplastic anemia, decreased white blood cell count, and a low platelet count.