Before taking phenytoin,
tell your doctor and pharmacist if you are allergic to phenytoin, other hydantoin medications such as ethotoin (Peganone) or fosphenytoin (Cerebyx), or any other medications. Also tell your doctor if you are allergic to carbamazepine (Carbatrol, Equetro, Tegretol, others), or if your doctor chose not to treat you with carbamazepine because laboratory testing showed that you have an inherited risk factor that makes it more likely that you will have an allergic reaction to carbamazepine. This risk factor may also increase the chance that you will have an allergic reaction to phenytoin.
tell your doctor if you are taking delavirdine (Rescriptor). Your doctor will probably tell you not to take phenytoin if you are taking this medication.
tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: albendazole (Albenza); amiodarone (Cordarone, Nexterone, Pacerone); anticoagulants ('blood thinners') such as warfarin (Coumadin, Jantoven); antifungal medications such as fluconazole (Diflucan), ketoconazole (Nizoral), itraconazole (Onmel, Sporanox), miconazole (Oravig), posaconazole (Noxafil), and voriconazole (Vfend); certain antivirals such as efavirenz (Sustiva, in Atripla), indinavir (Crixivan), lopinavir (in Kaletra), nelfinavir (Viracept), ritonavir (Norvir, in Kaletra), and saquinavir (Invirase); bleomycin; capecitabine (Xeloda); carboplatin; chloramphenicol; chlordiazepoxide (Librium, in Librax); chlorpropamide (Diabinese); cholesterol medications such as atorvastatin (Lipitor, in Caduet), fluvastatin (Lescol), and simvastatin (Zocor, in Vytorin); cisplatin; clozapine (Fazaclo, Versacloz); cyclosporine (Gengraf, Neoral, Sandimmune); diazepam (Valium); digoxin (Lanoxin); disulfiram (Antabuse); doxorubicin (Doxil); doxycycline (Doryx, Vibramycin); fluorouracil; fluoxetine (Prozac, Sarafem, in Symbyax, others); fluvoxamine (Luvox); folic acid; fosamprenavir (Lexiva); furosemide (Lasix); H2 antagonists such as cimetidine (Tagamet), famotidine (Pepcid), nizatidine (Axid), and ranitidine (Zantac); hormonal contraceptives (birth control pills, patches, rings, or injections); hormone replacement therapy (HRT); irinotecan (Camptosar); isoniazid (Laniazid, in Rifamate, in Rifater); medications for mental illness and nausea; other medications for seizures such as carbamazepine (Carbatrol, Equetro, Tegretol, others), ethosuximide (Zarontin), felbamate (Felbatol), lamotrigine (Lamictal), methsuximide (Celontin), oxcarbazepine (Trilepta), phenobarbital, topiramate (Topamax), and valproic acid (Depakene); methadone (Dolophine, Methadose); methotrexate (Otrexup, Rasuvo); methylphenidate (Daytrana, Concerta, Metadate, Ritalin); mexiletine; nifedipine (Adalat, Afeditab), nimodipine (Nymalize), nisoldipine (Sular); omeprazole (Prilosec); oral steroids such as dexamethasone, methylprednisolone (Medrol), prednisolone, and prednisone (Rayos); paclitaxel (Abraxane, Taxol); paroxetine (Paxil, Pexeva); praziquantel (Biltricide); quetiapine (Seroquel); quinidine (in Nuedexta); reserpine ; rifampin (Rifadin, Rimactane, in Rifamate, in Rifater); salicylate pain relievers such as aspirin, choline magnesium trisalicylate, choline salicylate, diflunisal, magnesium salicylate (Doan's, others), and salsalate; sertraline (Zoloft); sucralfate (Carafate); sulfa antibiotics; teniposide (Vumon); theophylline (Elixophyllin, Theo-24); ticlopidine; tolbutamide; trazodone; verapamil (Calan, Verelan, in Tarka); vigabatrin (Sabril); and vitamin D. Your doctor may need to change the doses of your medications or monitor you more carefully for side effects.
tell your doctor if you are taking antacids that contain calcium, magnesium, or aluminum (Maalox, Mylanta, Tums, others). Your doctor may tell you to allow some time to pass between taking the antacid and taking phenytoin.
tell your doctor what herbal products you are taking, especially St. John's wort.
tell your doctor if you have ever developed a liver problem while taking phenytoin. Your doctor will probably tell you not to take phenytoin again.
tell your doctor if you drink or have ever drunk large amounts of alcohol and if you have or have ever had diabetes, porphyria (condition in which certain natural substances build up in the body and may cause stomach pain, changes in thinking or behavior, or other symptoms), or kidney or liver disease.
tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. You should not become pregnant while you are taking phenytoin. Talk to your doctor about effective birth control methods that you can use during your treatment. If you become pregnant while taking phenytoin, call your doctor. Phenytoin may harm the fetus.
if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking phenytoin.
you should know that this medication may cause dizziness and problems with coordination. Do not drive a car or operate machinery until you know how this medication affects you.
talk to your doctor about the safe use of alcohol while you are taking this medication.
you should know that your mental health may change in unexpected ways and you may become suicidal (thinking about harming or killing yourself or planning or trying to do so) while you are taking phenytoin. A small number of adults and children 5 years of age and older (about 1 in 500 people) who took anticonvulsants such as phenytoin to treat various conditions during clinical studies became suicidal during their treatment. Some of these people developed suicidal thoughts and behavior as early as one week after they started taking the medication. There is a risk that you may experience changes in your mental health if you take an anticonvulsant medication such as phenytoin, but there may also be a risk that you will experience changes in your mental health if your condition is not treated. You and your doctor will decide whether the risks of taking an anticonvulsant medication are greater than the risks of not taking the medication. You, your family, or your caregiver should call your doctor right away if you experience any of the following symptoms: panic attacks; agitation or restlessness; new or worsening irritability, anxiety, or depression; acting on dangerous impulses; difficulty falling or staying asleep; aggressive, angry, or violent behavior; mania (frenzied, abnormally excited mood); talking or thinking about wanting to hurt yourself or to end your life; withdrawing from friends and family; preoccupation with death and dying; giving away prized possessions; or any other unusual changes in behavior or mood. Be sure that your family or caregiver knows which symptoms may be serious so they can call the doctor if you are unable to seek treatment on your own.
talk to your doctor about the best way to care for your teeth, gums, and mouth during your treatment with phenytoin. It is very important that you care for your mouth properly to decrease the risk of gum damage caused by phenytoin.