Phenytoin, sold in the United States under the brand names Dilantin and Phenytek, is an antiepileptic, or anticonvulsant, drug. It works by slowing down impulses in the brain that cause convulsions (fits or seizures), and may be prescribed to people with epilepsy or other seizure disorders.

Despite its widespread use today, however, the drug’s original discovery was accidental. Diphenylhydantoin was developed by scientists who were seeking to invent a new sedative. The drug’s powerful antiseizure effects were only noticed in 1938 after it failed to work as they had originally hoped.

Specifically. the scientists realized that the drug could be used to treat tonic-clonic (or grand mal) seizures (it is not effective for myoclonic, atonic, or absence seizures). It was marketed as Dilantin, and its generic name was later changed to phenytoin sodium. While Dilantin and generic phenytoin pills are available only in strengths of up to 100 milligrams, a newer brand called Phenytek comes in timed-release 300-milligram doses (each capsule containing three “mini-tabs” that release medication in stages), allowing patients to take one pill a day instead of two or three. Phenytoin is also available in chewable tablet form or as liquid medicine.

The drug can have numerous harmful side effects, including nausea and difficulty concentrating in the short term and rashes or excessive hair growth in the long term. Dilantin can also interact with other drugs, including antidepressants and antacids.

An overdose of phenytoin can be very dangerous or even fatal. Overdose symptoms may include twitching eyes; slurred speech; loss of balance; muscle stiffness, weakness, or tremor; nausea and vomiting; and slow or shallow breathing. Allergic reactions can be severe as well and may be indicated by fever, sore throat, a blistering skin rash, confusion, hallucinations, extreme thirst, or easy bruising or bleeding. Less-serious side effects are more likely to occur, such as twitching, a mild skin rash or itching, headache, joint pain, and swollen or tender gums.

ADDITIONAL FACTS

  1. Anyone taking an antiseizure medication should wear a medical alert bracelet or carry an ID card to alert doctors or medical workers in case of an emergency.
  2. The medication can lower blood sugar, so people with diabetes who take it should monitor their levels regularly.
  3. Phenytoin increases the risk of gum disease, so anyone taking it should brush and floss regularly.