Phenytoin is used to prevent and control seizures (also called an anticonvulsant or antiepileptic drug). It works by reducing the spread of seizure activity in the brain.
OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.
This drug may also be used to treat certain types of irregular heartbeats.
How to use Dilantin oral
Read the Medication Guide provided by your pharmacist before you start taking phenytoin and each time you get a refill. If you have any questions, ask your doctor or pharmacist.
Take this medication by mouth usually once a day or in divided doses as directed by your doctor. You may take it with food if stomach upset occurs. Take this medication with a full glass (8 ounces or 240 milliliters) of water unless your doctor directs you otherwise.
Swallow the capsules whole. Do not use the capsules if discolored.
Use this medication regularly in order to get the most benefit from it. It is important to take all doses on time to keep the amount of medicine in your body at a constant level. Remember to use it at the same time(s) each day. Dosage is based on your medical condition and response to therapy.
Products that contain calcium (e.g., antacids, calcium supplements) and nutritional tube-feeding (enteral) products may decrease the absorption of phenytoin. Do not take these products at the same time as your phenytoin dose. Separate liquid nutritional products at least 1 hour before and 1 hour after your phenytoin dose, or as directed by your doctor.
Headache, nausea, vomiting, constipation, dizziness, feeling of spinning, drowsiness, trouble sleeping, or nervousness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
Phenytoin may cause swelling and bleeding of the gums. Massage your gums and brush and floss your teeth regularly to minimize this problem. See your dentist regularly.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor immediately if any of these unlikely but serious side effects occur: unusual eye movements, loss of coordination, slurred speech, confusion, muscle twitching, double or blurred vision, tingling of the hands/feet, facial changes (e.g., swollen lips, butterfly-shaped rash around the nose/cheeks), excessive hair growth, increased thirst or urination, unusual tiredness, bone or joint pain, easily broken bones.
A small number of people who take anticonvulsants for any condition (such as seizure, bipolar disorder, pain) may experience depression, suicidal thoughts/attempts, or other mental/mood problems. Tell your doctor immediately if you or your family/caregiver notice any unusual/sudden changes in your mood, thoughts, or behavior including signs of depression, suicidal thoughts/attempts, thoughts about harming yourself.
For males, in the very unlikely event you have a painful or prolonged erection lasting 4 or more hours, stop using this drug and seek immediate medical attention, or permanent problems could occur.
Get medical help right away if any of these rare but very serious side effects occur: uncontrolled muscle movements, muscle weakness/pain, swollen glands (lymph nodes), stomach/abdominal pain, persistent nausea/vomiting, yellowing eyes or skin, dark urine, easy bruising/bleeding, signs of infection (e.g., persistent sore throat or fever), chest pain, trouble breathing, irregular heartbeat.
A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, high fever, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This drug should not be used with the following medications because very serious interactions may occur: azapropazone, delavirdine, dofetilide, etravirine, nisoldipine, rilpivirine.
If you are currently using any of these medications, tell your doctor or pharmacist before starting phenytoin.
Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: colesevelam, molindone, pyridoxine (vitamin B6), sucralfate, sulfa drugs, telithromycin, drugs affecting liver enzymes that remove phenytoin from your body (such as amiodarone, azole antifungals including itraconazole, cimetidine, macrolide antibiotics including erythromycin, estrogens, isoniazid, rifamycins including rifabutin, St. John's wort, other anti-seizure medicines including carbamazepine/phenobarbital/valproic acid).
Phenytoin can speed up the removal of many other drugs from your body by affecting certain liver enzymes. This can affect how well these other drugs work. These other drugs include: some drugs to treat cancer (e.g., imatinib, irinotecan), corticosteroids (e.g., prednisone), cyclosporine, felodipine, quetiapine, quinidine, theophylline, vitamin D, warfarin. This is not a complete list. Tell your doctor or pharmacist of all other drugs you take.
Also report the use of drugs which might increase seizure risk (decrease seizure threshold) such as: phenothiazines (e.g., thioridazine) or tricyclic antidepressants (e.g., amitriptyline), among others. Consult your doctor or pharmacist for details.
This medication may decrease the effectiveness of hormonal birth control such as pills, patch, or ring. This could cause pregnancy. Discuss with your doctor or pharmacist if you should use additional reliable birth control methods while using this medication. Also tell your doctor if you have any new spotting or breakthrough bleeding, because these may be signs that your birth control is not working well.