Long-term use of Phenytek and other forms of phenytoin has been found to cause weakening of the bones. Bone disease is even more likely if a combination of seizure medicines is used. People taking Phenytek should exercise, take vitamin D supplements, and eat foods rich in calcium. Some non-food sources of calcium, such as Tums and Os-Cal, reduce absorption of Phenytek. They can be used but should not be taken within about 2 hours after taking the Phenytek. (This restriction does not apply to food sources of calcium such as dairy products.) Many doctors now recommend bone-density studies for anyone taking Phenytek.

Other serious reactions to Phenytek are very rare but everyone who takes this medicine should at least be aware of them because a very small number of people have died because of them. A complete list of all reactions to phenytoin, the medicine in Phenytek, can be found in the package insert for Dilantin, but it is important to remember that most people who take it have none of these serious problems.

As with many other seizure medicines, there is a very small chance of developing a rash so serious that hospitalization may be required. (It has been estimated that this happens to 2 to 5 people out of each 10,000 who take Phenytek). Though the risk is small, call the doctor promptly if you notice a rash, since in a few cases these rashes are fatal.

In rare cases, allergic reactions to Phenytek can result in damage to the liver or bone marrow. The doctor may perform blood tests from time to time to look for early stages of this kind of damage.

Another rare reaction to Phenytek is disease of the lymph nodes. Tell the doctor about any fever, rash, or swollen, tender lymph glands. These usually are found in the neck, armpits, or groin.

On July 10, 2008, an advisory panel was convened by the Food and Drug Administration (FDA) to review data that the FDA had previously collected from drug studies showing an association between many of the antiepileptic drugs (AEDs) and suicidal ideation and behavior, which together are called suicidality. According to the FDA’s Alert, among the patients with epilepsy in these drug studies, 1 out of 1000 people taking the placebo (inactive substance) showed suicidality compared to approximately 3.5 out of 1000 people who took an AED. The FDA advisory panel voted to accept the FDA's data at its meeting on July 10. The FDA has provided the following information for patients, family members, and caregivers at www.fda.gov/cder/drug/InfoSheets/HCP/antiepilepticsHCP.htm.

• Taking antiepileptic medicines may increase the risk of having suicidal thoughts or actions;
• Do not make any changes to the medication regimen without first talking with the responsible healthcare professional;
• Pay close attention to any day-to-day changes in mood, behavior and actions. These changes can happen very quickly so it is important to be mindful of any sudden differences.
• Be aware of common warning signs that might be a signal for risk of suicide. Some of these are:
  • Talking or thinking about wanting to hurt yourself or end your life
  • Withdrawing from friends and family
  • Becoming depressed or having your depression get worse
  • Becoming preoccupied with death and dying
  • Giving away prized possessions

We again urge patients and families to contact their doctor before stopping an epilepsy medication because this may possibly lead to seizures and worsening of mood.

Reviewed July 2008 by Steven C. Schachter, MD, epilepsy.com Editorial Board.