Phenytoin Health Article

Definition

Phenytoin is an anticonvulsant, a drug that acts to prevent seizures. In the United States, phenytoin is sold under the brand name Dilantin.

Purpose

Phenytoin helps prevent some types of seizure activity. It is often used to aid in controlling nerve pain associated with some cancers and cancer treatments. Nerve pain causes a burning, tingling sensation. Phenytoin also may be ordered to control a rapid or irregular heart rate. Phenytoin may be given to stop uncontrolled seizures. It may be used during brain surgery to prevent seizure activity. Additional uses are under study.

Description

Phenytoin works on areas of the brain to limit electrical discharges and stabilize cellular activity. Like many drugs that control seizures, it also has proven helpful in managing nerve pain.

Recommended dosage

The dose ordered depends on blood levels of the drug determined during routine monitoring. For pain, doctors usually order 200-500 mg per day, either at bedtime or in divided doses. Patients usually start on a low dose. Depending on the patient's response and drug blood levels, the dose may be increased. For seizures, patients are usually started at 100 mg, three times per day. Blood is drawn to check the level of phenytoin in seven to 10 days. The dose is adjusted accordingly. The doctor may prescribe a dose based on an older person's weight. A child's dose also is based on his or her weight.

It is very important that this drug be used exactly as directed. This medication should be taken at the same time every day. Patients should take a missed dose as soon as it is noted. But patients should not take two doses within four hours of each other. This medication should be stored in a dry place, not in the bathroom.

Precautions

Patients should not suddenly stop taking this medication. The abrupt withdrawal of phenytoin could trigger seizures. Patients should not crush or break extended-release drugs. Chewable tablets should be chewed before swallowing. Other pills should be swallowed whole. Older adults may be more prone to adverse effects than younger people. Patients should not change brands without approval of the doctor.

Phenytoin should not be taken by patients who are allergic to this drug. People with slow heart rates, certain other heart conditions, or a flaking, open skin condition also should not take it. Phenytoin may be used cautiously for patients with asthma, allergies, limited kidney or liver function, heart disease, and blood disorders. It also should be used with caution in those with alcoholism, diabetes mellitus, lupus, poor thyroid function, or porphyria, a rare metabolic disorder. Pregnant women should discuss the risks and benefits of this medication with the doctor. It has been associated with birth defects and possibly cancer in children born to women taking the drug. Expectant mothers who are taking it to prevent seizures should not abruptly stop the drug. Those using it for pain control should discuss its continued use with the doctor. Patients on this drug should not breast feed.