General Information: Dilantin is an anticonvulsant drug that has been used since 1938. Dilantin is used to treat grand mal, complex partial, and mixed seizures.

Formulations: Dilantin is available in the following formulations:

• 50 mg chewable infatablets (scored). Scored tablets can be cut in half.
• 30 mg capsule
• 100 mg capsule
• 125 mg/5ml liquid suspension

The suspension must be shaken very well immediately before each use. The active part of the suspension can "settleout," resulting in higher concentration of the drug at the bottom of the bottle unless it is thoroughly mixed by shaking.

Dosage: The usual dosage of Dilantin is 4-8 mg/kilogram of body weight per day. Dilantin is usually taken two times a day.

Therapeutic Drug Levels: The blood level of Dilantin that isfound to prevent seizures in most people is between 10-20µg/ml.

Side Effects: All drugs have side effects. Two common problems associated with Dilantin in children are stimulation of hair growth on the arms or back, which is usually mild and insignificant, and thickening or enlargement of gum tissue (gum hypertrophy). The effect on gum tissue is usually related to the dosage, and will consistently occur with high dosages when used for prolonged periods. People differ in their sensitivity to the effects of Dilantin on the gums. It can be diminished to some degree with good dental hygiene (frequent brushing and daily flossing) but cannot be entirely avoided. When gum enlargement is mild, it creates no problem. But when it is severe, it may require a surgical procedure by the dentist to excise the excessive gum tissue. With long-term use of Dilantin, there can also be very slow thickening of soft-tissue of the lips and other facial parts.

A small percentage of children will be "allergic" to Dilantin. In this case the allergic reaction is not related to the dose and the Dilantin is discontinued. The most common symptom of allergy is a rash that often resembles the rash of measles. This rash will usually appear 7-20 days after the drug is first started. In some instances, the rash can be severe and associated with fever. These symptoms however will resolve within days after the drug is stopped.

On rare occasions, Dilantin can decrease the blood cell count. These cells fight infection and clot blood. For this reason, children taking Dilantin should have periodic blood counts (CBC).

In addition to the above, there are other possible side effects of Dilantin, most of which are rare or are not clinically significant. Dilantin has an effect on Vitamin D metabolism. In children who receive typical sunshine exposure, Vitamin D metabolism remains unchanged. Children who are never exposed to the sun (bed ridden), however, may need their serum calcium and phosphorus checked occasionally.

Toxic symptoms are symptoms experienced when the blood Dilantin level is too high. Toxic symptoms vary from child to child but may include repeated vomiting, staggering, slurred speech, nystagmus (abnormal jerking of the colored part of the eyes when looking to either side), and listlessness or drowsiness. Double vision can also occur and is sometimes the only apparent sign of toxicity.

Common Labs: Scheduled monitoring of blood cell counts and Dilantin levels have increased the safety and efficacy of Dilantin. We will usually recommend checking a Dilantin level 4 weeks after reaching a therapeutic dose, and every 4-12 months thereafter. We also recommend checking a complete blood count (CBC) approximately every 4-12 months.

Drug Interactions: There are many drugs that may increase or decrease Dilantin blood levels or which Dilantin may affect. Generally, these interactions are not clinicially important in the pediatric population. Serum drug levels are especially helpful when possible drug interactions are suspected. The most commonly occurring drug interactions are listed below:

1. Some of the more common drugs that may increase Dilantin levels include: acute alcohol intake, estrogens, H2-antagonists, and sulfonamides. Also the development of certain types of liver disease can cause the blood level to rise, because Dilantin is metabolized by the liver.
2. Some of the more common drugs that may decrease Dilantin levels are Tegretol, and chronic alcohol abuse. Calcium-containing antacids can cause absorption problems. If a child is taking Dilantin and a calcium-containing antacid, the two drugs should be staggered to avoid absorption problems.
3. Drugs whose efficacy is impaired by the Dilantin include:
   • corticosteroids
   • coumadin anticoagulants
   • Digoxin
   • Doxycycline
   • estrogens
   • Furosemide
   • oral contraceptives
   • Quinidine
   • Rifampin
   • Vitamin D
   • Theophylline

You should inform your Neurologist if your child is taking any of these types of medications. Also your local pharmacist can often be helpful in informing you of known drug interactions between the medications your child takes.

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