Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Allergy: Some people who are allergic to carbamazepine or barbiturates also experience allergic reactions to phenytoin. Before you take phenytoin, inform your doctor about any previous adverse reactions you have had to medications, especially other medications for seizures. Contact your doctor at once if you experience signs of an allergic reaction, such as skin rash, itching, difficulty breathing or swelling of the face and throat.
Dental hygiene: Because phenytoin can cause swollen and bleeding gums, it is important to practice good dental hygiene by flossing, brushing, and visiting your dentist regularly. Talk to your doctor to learn more about how to take care of your mouth, gums, and teeth while taking this medication.
Diabetes: Phenytoin may have an effect on the action of medications used to lower blood sugar for people with diabetes. If you have diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. It may be necessary to monitor your blood sugar more closely when starting or stopping phenytoin treatment.
Drowsiness/reduced alertness: Some people who take phenytoin may become drowsy. Avoid activities that require complete mental alertness, judgment, and physical coordination (such as driving a car or performing hazardous tasks) until you establish how you are affected by phenytoin.
Hypersensitivity syndrome: A severe allergic reaction called hypersensitivity syndrome has occurred for some people with the use of phenytoin. Stop taking the medication and get immediate medical attention if you have symptoms of a severe allergic reaction, including fever, swollen glands, yellowing of the skin or eyes, or flu-like symptoms with skin rash or blistering.
Liver function: Some people have reported liver problems with the use of phenytoin. These cases have been associated with an allergic reaction that includes fever, skin rashes or hives, or swollen lymph glands. The reaction usually occurs within the first 2 months of treatment. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.
Osteoporosis: Long term use of anti-seizure medications, including phenytoin may affect the strength of your bones, because these medication reduce the amount of vitamin D available for your body to use. If you have or are at risk for developing osteoporosis, discuss with your doctor the need to take additional vitamin D.
Other medications: Many medications interact with phenytoin causing decreased effectiveness or increased side effects. If you are taking phenytoin, consult with your doctor or pharmacist before taking any other medications or drinking alcoholic beverages.
Regular dosing: Remember that when you are taking phenytoin, it is very important to take the medication exactly as prescribed. Inform your doctor of any condition that prevents you from taking the medication as prescribed (e.g., surgery, illness, difficulty swallowing).
Stopping the medication: Do not stop taking phenytoin without consulting your doctor. Stopping the medication suddenly may cause an increase in the number or severity of seizures. If it is necessary to stop taking this medication, talk to your doctor about how to gradually reduce the dose of the medication before completely stopping.
Suicidal thoughts and behaviour: Some people taking anti-seizure medications may have suicidal thoughts or behaviour. If this happens to you or you notice this in a family member who is taking this medication, contact your doctor immediately. You should be closely monitored by your doctor for emotional and behaviour changes while taking this medication.
Pregnancy: When phenytoin is taken during pregnancy, it may cause harm to the developing baby. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking phenytoin, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.