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Phenytoin

Phenytoin

Overview

Dilantin is one of the oldest and best studied anti-seizure medications on the market. Although it was first developed in 1908, the drug’s ability to prevent epilepsy wasn’t discovered until 1938.

It works in part by stabilizing nerve cells and making them less excitable. It also exerts a similar action in the heart and is sometimes prescribed for irregular rhythms or a painful nerve condition that affects the face called trigeminal neuralgia.

Side Effects and Interactions of Dilantin

Dilantin can cause a number of side effects which are more common at higher doses.

Symptoms to be alert for include slurred speech, confusion, clumsiness, tremor, poor coordination, dizziness, drowsiness, uncontrollable eye movements, blurred vision, muscle twitching,
insomnia, headaches, nervousness and hyperactivity. If these adverse reactions do not disappear within a few weeks of starting therapy contact your physician promptly and request a blood test.

If you develop a skin rash call your doctor immediately. This side effect usually calls for the discontinuation of the medicine, though this may require a gradual tapering of the dose and the substitution of another drug.

Other less common side effects include chest pain, nausea, diarrhea or constipation, water retention, numbness or tingling of hands and feet, hair loss, fever, blood changes, weight gain, and liver problems.

Some women note unwanted hair growth on their faces or bodies. Report any symptoms to your physician promptly. Many people who take this medication for long periods of time experience overgrowth of the gums. In this case good dental hygiene is especially important. Frequent dental visits are advisable.

A large number of over-the-counter and prescription medications may interact with Dilantin in a dangerous way. This anticonvulsant can interfere with the transplant drug Sandimmune, increasing the risk of rejection. Certain other anticonvulsants may increase Dilantin’s toxicity, as may Prozac or related antidepressants.

Some drugs, such as theophylline or tuberculosis drugs, can reduce the effectiveness of Dilantin and make people more vulnerable to seizures. In addition, Dilantin can interfere with the effectiveness of many other medications, including doxycycline, theophylline, birth control pills and the heart medicine Cordarone.

Other drugs that interact with Dilantin include alcohol, calcium-based antacids, pain relievers containing acetaminophen, folic acid, quinidine heart drugs, the blood thinner Coumadin, certain antidepressants and the ulcer medicines Tagamet and Prilosec.

Do not take any other medication without first checking with your physician and pharmacist.

Special Precautions When Using Dilantin

Determining the proper dose of Dilantin is not always easy. Some individuals metabolize this medicine more rapidly than normal and may need higher amounts. Others, especially older people or those with liver problems may need lower doses or a different anti-seizure medication to avoid toxicity.

Periodic blood tests can help determine if the dose is appropriate. Diabetics will need to be even more careful than usual in monitoring blood sugar. Dilantin may interfere with normal control.

Taking the Medicine

Dilantin is best taken at meal time to increase absorption and reduce the risk of stomach upset. Do not swallow your pill with milk, however, or take it at the same time you eat foods high in calcium, as this mineral may reduce the effectiveness of your medicine.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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