Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For hydantoin anticonvulsants, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to any hydantoin anticonvulsant medicine. Also tell your health care professional if you are allergic to any other substance, such as foods, preservatives, or dyes.

Pregnancy—Although most mothers who take medicine for seizure control deliver normal babies, there have been reports of increased birth defects when these medicines were used during pregnancy. It is not definitely known if any of these medicines are the cause of such problems.

Also, pregnancy may cause a change in the way hydantoin anticonvulsants are absorbed in your body. You may have more seizures, even though you are taking your medicine regularly. Your doctor may need to increase the anticonvulsant dose during your pregnancy.

In addition, when taken during pregnancy, this medicine may cause a bleeding problem in the mother during delivery and in the newborn. This may be prevented by giving vitamin K to the mother during delivery, and to the baby immediately after birth.

Breast-feeding—Ethotoin and phenytoin pass into the breast milk in small amounts. It is not known whether mephenytoin passes into breast milk. Be sure you have discussed the risks and benefits of the medicine with your doctor.

Children—Some side effects, especially bleeding, tender, or enlarged gums and enlarged facial features, are more likely to occur in children and young adults. Also, unusual and excessive hair growth may occur, which is more noticeable in young girls. In addition, some children may not do as well in school after using high doses of this medicine for a long time.

Older adults—Some medicines may affect older patients differently than they do younger patients. Overdose is more likely to occur in elderly patients and in patients with liver disease.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking or receiving hydantoin anticonvulsants, it is especially important that your health care professional know if you are taking any of the following:

• Alcohol or
• Central nervous system (CNS) depressants (medicine that causes drowsiness)—Long-term use of alcohol may decrease the blood levels of hydantoin anticonvulsants, resulting in decreased effects; use of hydantoin anticonvulsants in cases where a large amount of alcohol is consumed may increase the blood levels of the hydantoin, resulting in an increased risk of side effects

• Amiodarone (e.g., Cordarone)—Use with phenytoin and possibly with other hydantoin anticonvulsants may increase blood levels of the hydantoin, resulting in an increase in serious side effects

• Antacids or
• Medicine containing calcium—Use of antacids or calcium supplements may decrease the absorption of phenytoin; doses of antacids and phenytoin or calcium supplements and phenytoin should be taken 2 to 3 hours apart

• Anticoagulants (blood thinners) or
• Chloramphenicol (e.g., Chloromycetin) or
• Cimetidine (e.g., Tagamet) or
• Disulfiram (e.g., Antabuse) (medicine for alcoholism) or
• Isoniazid (INH) (e.g., Nydrazid) or
• Fluconazole (e.g., Diflucan) or
• Fluoxetine (e.g., Prozac) or
• Itraconazole (e.g., Sporanox) or
• Ketoconazole (e.g., Nizoral) or
• Miconazole (e.g., Monistat) or
• Phenylbutazone (e.g., Butazolidin) or
• Sulfonamides (sulfa drugs)—Blood levels of hydantoin anticonvulsants may be increased, increasing the risk of serious side effects; hydantoin anticonvulsants may increase the effects of the anticoagulants at first, but with continued use may decrease the effects of these medicines

• Corticosteroids (cortisone-like medicines) or
• Estrogens (female hormones) or
• Oral contraceptives (birth-control pills) containing estrogens or progestins or
• Progestin injection contraceptives (e.g., Depo-Provera) or
• Progestin implant contraceptives (e.g., Norplant)—Hydantoin anticonvulsants may decrease the effects of these medicines; use of hydantoin anticonvulsants with estrogen- or progestin-containing contraceptives may result in breakthrough bleeding and contraceptive failure; additional birth control measures may be needed to decrease the risk of pregnancy

• Diazoxide (e.g., Proglycem)—Use with hydantoin anticonvulsants may decrease the effects of both medicines; therefore, these medicines should not be taken together

• Felbamate (e.g., Felbatrol)—Blood levels of hydantoin anticonvulsants may be increased, and blood levels of felbamate may be decreased. Your doctor may need to adjust your dosage

• Lidocaine—Risk of slow heartbeat may be increased. Other effects of lidocaine may be decreased because hydantoin anticonvulsants may cause it to be removed from the body more quickly

• Methadone (e.g., Dolophine, Methadose)—Long-term use of phenytoin may bring on withdrawal symptoms in patients being treated for drug dependence

• Phenacemide (e.g., Phenurone)—Use with hydantoin anticonvulsants may increase the risk of serious side effects

• Rifampin (e.g., Rifadin)—Use with phenytoin may decrease the effects of phenytoin; your doctor may need to adjust your dosage

• Streptozocin (e.g., Zanosar)—Phenytoin may decrease the effects of streptozocin; therefore, these medicines should not be used together

• Sucralfate (e.g., Carafate)—Use of sucralfate may decrease the absorption of hydantoin anticonvulsants

• Theophylline (e.g., Theo-Dur)—Hydantoin anticonvulsants may make this medicine less effective

• Valproic acid (e.g., Depakene, Depakote)—Use with phenytoin, and possibly other hydantoin anticonvulsants, may increase seizure frequency and increase the risk of serious side effects affecting the liver, especially in infants

Other medical problems—The presence of other medical problems may affect the use of hydantoin anticonvulsants. Make sure you tell your doctor if you have any other medical problems, especially:

• Alcohol abuse—Blood levels of phenytoin may be decreased, decreasing its effects

• Blood disease—Risk of serious infections rarely may be increased by hydantoin anticonvulsants

• Diabetes mellitus (sugar diabetes) or
• Porphyria or
• Systemic lupus erythematosus—Hydantoin anticonvulsants may make the condition worse

• Fever above 101 °F for longer than 24 hours—Blood levels of hydantoin anticonvulsants may be decreased, decreasing the medicine's effects

• Heart disease—Administration of phenytoin by injection may change the rhythm of the heart

• Kidney disease or
• Liver disease—Blood levels of hydantoin anticonvulsants may be increased, leading to an increase in serious side effects

• Thyroid disease—Blood levels of thyroid hormones may be decreased