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 (also known as grand mal seizures) and focal seizures, but not absence seizures. The intravenous form, fosphenytoin, 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 roughly 24 hours. Blood levels can be measured to determine the proper dose.
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Pronunciation | /fəˈnɪtoʊɪn, ˈfɛnɪtɔɪn/ |
Trade names | Dilantin, others |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682022 |
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Routes of administration | By mouth, intravenous |
Drug class | Anticonvulsant |
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Bioavailability | 70–100% (oral), 24.4% (rectal) |
Protein binding | 95% |
Metabolism | Liver |
Onset of action | 10–30 min (intravenous) |
Elimination half-life | 10–22 hours |
Duration of action | 24 hours |
Excretion | Urinary (23–70%), bile |
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ECHA InfoCard | 100.000.298 |
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Formula | C15H12N2O2 |
Molar mass | 252.273 g·mol−1 |
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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. Phenytoin is available as a generic medication. In 2020, it was the 260th most commonly prescribed medication in the United States, with more than 1 million prescriptions.