Phenytek has been used for many years to treat children with partial and generalized tonic-clonic seizures. It can cause side effects from high doses and allergic reactions at any dosage. Often it is not chosen as a first-choice medication for young children because it may have troublesome effects on appearance when used for a long time.

The first sign of an allergic reaction to Phenytek is a rash, so if you see any skin problems, call a doctor immediately. In rare cases, allergic reactions to Phenytek can result in damage to the liver or bone marrow.

The most common side effect related to Phenytek in children is jerky movements of the eyes called nystagmus. These movements often do not interfere with a child's vision.

Other side effects from high doses include unsteadiness in the feet and hands, sleepiness, and vomiting. These may be avoidable if the dosage is increased slowly. They should quickly disappear when the dosage is reduced.

In a few children, Phenytek causes problems with thinking or behavior, mood change, slow or clumsy movements, or a loss of energy.

One fairly common side effect in children is overgrowth of the gums. This occurs in almost one-half of children. Braces can make this problem even more severe. Careful brushing, daily flossing and regular visits to the dental hygienist will diminish the swelling. A few children need gum surgery.

Some young people who take fairly high doses of Phenytek also have increased growth and darkening of hair on the face and body, called hirsutism. These effects are especially troublesome for young women.

Children usually start taking phenytoin, the medicine in Phenytek, with a dose of 5 milligrams (mg) per kilogram (kg, equal to 2.2 pounds) of their body weight per day. For most children, this is less than the smallest Phenytek capsule (200 mg), so they will probably start by taking another form such as Dilantin. For many children, the dose is later increased until it totals 200 to 300 mg per day. These children then can use Phenytek instead, if they are able to swallow capsules.