Phenytoin, Oral/Injection

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KEY POINTS

• This medicine is used to control seizures caused by certain types of epilepsy. Take it exactly as directed.
• This medicine may increase suicidal thoughts or actions in some people.
• Keep all appointments for checkups to see how this medicine affects you.
• This medicine may cause unwanted side effects. Tell your healthcare provider if you have any side effects that are serious, continue, or get worse. People of Asian ancestry may be at high risk of a serious skin reaction from this medicine.
• This medicine may interact with many other medicines. Tell all healthcare providers who treat you about all the prescription medicines, nonprescription medicines, supplements, natural remedies, and vitamins that you take. Carry some form of ID stating that you have seizures and are taking this medicine.

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What are other names for this medicine?

Type of medicine: hydantoin antiseizure

Generic and brand names: phenytoin, oral; phenytoin, injection; Dilantin; Dilantin-125; Phenytek; Dilantin 50 mg Chewables; Dilantin Infatabs

What is this medicine used for?

This medicine is used to control seizures caused by certain types of epilepsy.

This medicine may be used to treat other conditions as determined by your healthcare provider.

What should my healthcare provider know before I take this medicine?

Before taking this medicine, tell your healthcare provider if you have ever had:

• An allergic reaction to any medicine
• A blood disorder
• Depression, mood problems, or thoughts of suicide
• Diabetes
• A vitamin D deficiency or any other problem that causes thinning of the bones
• Heart disease or an irregular heartbeat
• High or low blood pressure
• Liver or kidney disease
• Lupus
• Porphyria (nerve pain or sensitivity to sunlight)
• Problems with alcohol abuse
• Thyroid problems

If you are of Asian ancestry, you may be at high risk of a serious skin reaction. You may need a blood test before you start taking the medicine. Talk with your provider about this.

You should not take this medicine if you are also taking delavirdine (Rescriptor).

Females of childbearing age: This medicine is not usually given to pregnant women because it can harm the baby. If you are pregnant, tell your healthcare provider. Do not become pregnant during treatment with this medicine. If you become pregnant, contact your healthcare provider right away. Do not breast-feed while you are receiving this medicine.

How do I use it?

Read the Medication Guide that comes in the medicine package when you start taking this medicine and each time you get a refill.

Check the label on the medicine for directions about your specific dose. Take this medicine exactly as your healthcare provider prescribes. This medicine must be taken regularly every day to control seizures. Do not stop taking this medicine without your healthcare provider's approval. You may have to gradually reduce your dosage. If you stop taking the medicine too quickly, your seizures may increase.

Do not switch brands or types of this medicine (like tablets or liquid) unless your healthcare provider instructs you to. They may not work the same.

Check with your healthcare provider before using this medicine in children.

You may take this medicine with or without food. Taking it with meals may lessen the chance the drug will upset your stomach.

This medicine comes in long-acting capsules, chewable tablets, and liquid forms. If you have long-acting capsules, do not break, crush, or chew them. Swallow them whole. Do not take capsules that are discolored.

If you are taking the chewable tablet you may crush or chew the tablets or swallow them whole.

If you have the liquid form, shake the bottle well before using. Use the measuring spoon, cup, dropper, or oral syringe that comes with the medicine, or ask your pharmacist for one. Do not use a kitchen spoon because the dose may not be correct.

If you are taking tube feedings, you should hold the feedings 1 to 2 hours before and after taking this medicine or as instructed by your healthcare provider. Talk with your healthcare provider about this.

The injection form of this medicine is given by your healthcare provider. You will be monitored closely while receiving the injection form of this medicine.

What if I miss a dose?

Do not miss a dose. If you miss a dose, take it as soon as you remember unless it is almost time for the next scheduled dose. In that case, skip the missed dose and take the next one as directed. Do not take double doses. If you are not sure of what to do if you miss a dose, or if you miss more than one dose, contact your healthcare provider.

What if I overdose?

If you or anyone else has intentionally taken too much of this medicine, call 911 or go to the emergency room right away. If you pass out, have seizures, weakness or confusion, or have trouble breathing, call 911. If you think that you or anyone else may have taken too much of this medicine, call the poison control center. Do this even if there are no signs of discomfort or poisoning. The poison control center number is 800-222-1222.

Symptoms of an acute overdose may include: twitching eye movements, slurred speech, loss of balance, tremors, muscle stiffness, weakness, nausea, vomiting, lightheadedness, fainting, slow or shallow breathing.

What should I watch out for?

Antiseizure medicines may increase suicidal thoughts or actions in some people. Call your healthcare provider right away if you have new or increased thoughts of suicide, new or worsening depression, or any unusual changes in mood or behavior.

Do not start or stop taking any other medicine without your healthcare provider’s advice.

This medicine may make you drowsy or dizzy. Do not drive or operate machinery unless you are fully alert.

You will need to have blood tests and checkups regularly to see how this medicine affects you. Keep all appointments.

This medicine may affect your vitamin D level and cause problems with your bones. Talk with your healthcare provider about this.

Follow your healthcare provider's instructions about diet and taking vitamin supplements.

Carry some form of ID stating that you have seizures and are taking an antiseizure medicine.

This medicine may increase the effects of alcohol and other drugs that slow down your nervous system. Do not drink alcohol or take other medicines unless your healthcare provider approves.

This medicine may cause swelling and irritation of your gums. Ask your healthcare provider or dentist about proper dental care.

Adults over the age of 65 may be at greater risk for side effects. Talk with your healthcare provider about this.

Birth control medicines may not work properly while taking this medicine. Talk to your healthcare provider about other forms of birth control.

If you need emergency care, surgery, lab tests, or dental work, tell the healthcare provider or dentist you are taking this medicine.

If you have diabetes: This medicine may affect your blood sugar level and change the amount of insulin or other diabetes medicines you may need. Talk to your healthcare provider about this.

What are the possible side effects?

Along with its needed effects, your medicine may cause some unwanted side effects. Some side effects may be very serious. Some side effects may go away as your body adjusts to the medicine. Tell your healthcare provider if you have any side effects that continue or get worse.

Life-threatening (Report these to your healthcare provider right away. If you cannot reach your healthcare provider right away, get emergency medical care or call 911 for help.): Allergic reaction (hives; itching; rash; trouble breathing; chest pain or tightness in your chest; swelling of your lips, tongue, and throat).

Serious (Report these to your healthcare provider right away.): Severe stomach pain, nausea, or vomiting; confusion; unusual mood or behavior changes; new or worsening depression or anxiety; thoughts of suicide; vision problems; uncontrollable eye or muscle twitches; slurred speech or trouble walking; increased seizures; slow, fast, or irregular heartbeat; skin rash, peeling, or blisters; chest pain; strange feelings in your hands or feet; trembling; trouble swallowing or breathing; unexplained swelling; severe dizziness; dark urine; light-colored bowel movements; unusual loss of appetite; mouth sores; red or irritated eyes; sore throat; fever; unusual bruising or bleeding; unusual tiredness or weakness; severe muscle pain; yellowing of your skin or eyes; swollen or tender glands; changes in urination; severe gum swelling or pain; extreme thirst or hunger; pain, redness, discoloration, or swelling around the injection site.

Other: Slight drowsiness or dizziness, trouble sleeping, mild nausea or vomiting, constipation, diarrhea, mild nervousness, headache, metallic taste in your mouth.

What products might interact with this medicine?

When you take this medicine with other medicines, it can change the way this or any of the other medicines work. Nonprescription medicines, vitamins, natural remedies, and certain foods may also interact. Using these products together might cause harmful side effects. Talk to your healthcare provider if you are taking:

• Acetaminophen and medicines that contain acetaminophen
• Acetazolamide (Diamox)
• Albendazole (Albenza)
• Alcohol
• Alfuzosin (Uroxatral)
• Antacids
• Antianxiety medicines such as alprazolam (Xanax), chlordiazepoxide, clonazepam (Klonopin), clorazepate (Gen-Xene, Tranxene), diazepam (Valium), lorazepam (Ativan), and oxazepam
• Antibiotics such as bedaquiline (Sirturo), chloramphenicol, ciprofloxacin (Cipro), clarithromycin (Biaxin), doxycycline (Doryx, Monodox, Vibramycin), erythromycin (E.E.S., Ery-Tab, Erythrocin), isoniazid, metronidazole, rifabutin (Mycobutin), rifampin (Rifadin), rifapentine (Priftin), sulfadiazine, and sulfamethoxazole/trimethoprim (Bactrim, Septra)
• Antidepressants such as amitriptyline, citalopram (Celexa), clomipramine, desipramine (Norpramin), desvenlafaxine (Pristiq), duloxetine (Cymbalta), escitalopram (Lexapro), fluoxetine (Prozac), fluvoxamine (Luvox), imipramine (Tofranil), nortriptyline (Pamelor), protriptyline, sertraline (Zoloft), trazodone, and venlafaxine (Effexor)
• Antifungal medicines such as fluconazole (Diflucan), itraconazole (Sporanox), ketoconazole (Nizoral), miconazole (Monistat, Oravig), posaconazole (Noxafil), and voriconazole (Vfend)
• Antihistamines such as azelastine (Astelin, Astepro), chlorpheniramine (Chlor-Trimeton), diphenhydramine (Benadryl), and hydroxyzine (Vistaril)
• Antipsychotic medicines such as aripiprazole (Abilify), asenapine (Saphris), chlorpromazine, clozapine (Clozaril, FazaClo), fluphenazine, haloperidol (Haldol), iloperidone (Fanapt), lurasidone (Latuda), olanzapine (Zyprexa), paliperidone (Invega), perphenazine, pimozide (Orap), quetiapine (Seroquel), risperidone (Risperdal), thioridazine, trifluoperazine, and ziprasidone (Geodon)
• Antiviral medicines such as daclatasvir (Daklinza), ledipasvir/sofosbuvir (Harvoni), ombitasvir/paritaprevir/ritonavir/dasabuvir (Viekira), and simeprevir (Olysio)
• Apremilast (Otezla)
• Aspirin and other salicylates
• Bupropion (Aplenzin, Forfivo, Wellbutrin, Buproban, Zyban)
• Calcium or vitamin D supplements
• Cancer medicines such as abiraterone (Zytiga), axitinib (Inlyta), bleomycin, bortezomib (Velcade), brentuximab (Adcetris), busulfan (Busulfex, Myleran), capecitabine (Xeloda), carboplatin, ceritinib (Zykadia), cisplatin, crizotinib (Xalkori), dasatinib (Sprycel), doxorubicin (Doxil), enzalutamide (Xtandi), erlotinib (Tarceva), etoposide, exemestane (Aromasin), fluorouracil (Adrucil, Carac, Efudex, Fluoroplex), gefitinib (Iressa), idelalisib (Zydelig), imatinib (Gleevec), irinotecan (Camptosar), lapatinib (Tykerb), nilotinib (Tasigna), paclitaxel (Abraxane, Taxol), pazopanib (Votrient), romidepsin (Istodax), sorafenib (Nexavar), sunitinib (Sutent), teniposide, toremifene (Fareston), vandetanib (Caprelsa), and vemurafenib (Zelboraf)
• Cholesterol-lowering medicines such as atorvastatin (Lipitor), colesevelam (Welchol), fluvastatin (Lescol), gemfibrozil (Lopid), lovastatin (Altoprev), pravastatin (Pravachol), rosuvastatin (Crestor), and simvastatin (Zocor)
• Corticosteroids such as betamethasone, dexamethasone, hydrocortisone (A-Hydrocort, Cortef), methylprednisolone (Medrol, Solu-Medrol), and prednisone (Prednisone Intensol)
• Cystic fibrosis medicines such as ivacaftor (Kalydeco) and lumacaftor/ivacaftor (Orkambi)
• Diabetes medicines such as acarbose (Precose), chlorpropamide, glimepiride (Amaryl), glipizide (Glucotrol), glyburide (Glynase), linagliptin (Tradjenta), metformin (Fortamet, Glucophage, Riomet), nateglinide (Starlix), pioglitazone (Actos), repaglinide (Prandin), rosiglitazone (Avandia), saxagliptin (Onglyza), sitagliptin (Januvia), and tolbutamide
• Diazoxide (Proglycem)
• Diclofenac (Cambia, Voltaren, Zipsor)
• Disulfiram (Antabuse)
• Diuretics (water pills) such as bumetanide, furosemide (Lasix), and torsemide (Demadex)
• Doxepin (Silenor)
• Eliglustat (Cerdelga)
• Erectile dysfunction medicines such as avanafil (Stendra), sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra, Staxyn)
• Everolimus (Afinitor, Zortress)
• Flibanserin (Addyi)
• Folic acid or folate
• Heart medicines such as amiodarone (Cordarone, Pacerone), amlodipine (Norvasc), amlodipine/atorvastatin (Caduet), digoxin (Lanoxin), diltiazem (Cardizem, Cartia, Tiazac), dronedarone (Multaq), felodipine, mexiletine, nifedipine (Adalat CC, Procardia), nisoldipine (Sular), quinidine, ranolazine (Ranexa), reserpine, and verapamil (Calan, Covera, Verelan)
• HIV medicines such as atazanavir (Reyataz), cobicistat (Tybost), darunavir (Prezista), delavirdine (Rescriptor), efavirenz (Sustiva), etravirine (Intelence), fosamprenavir (Lexiva), indinavir (Crixivan), lopinavir/ritonavir (Kaletra), maraviroc (Selzentry), nelfinavir (Viracept), nevirapine (Viramune), rilpivirine (Edurant), ritonavir (Norvir), saquinavir (Invirase), stavudine (Zerit), and tipranavir (Aptivus)
• Hormonal birth control implants, IUDs, patches, pills, shots, and vaginal rings, and conjugated estrogen (Premarin, Premphase, Prempro), esterified estrogen (Estratab, Menest), estradiol (Climara, Estrace, Estraderm, Vivelle), and estropipate (Ogen)
• Immunosuppressants such as cyclosporine (Gengraf, Neoral, Sandimmune), sirolimus (Rapamune), and tacrolimus (Astagraf, Prograf, Protopic)
• Levodopa/carbidopa (Duopa, Rytary, Sinemet)
• Lithium (Lithobid)
• Malaria medicines such as artemether/lumefantrine (Coartem), chloroquine, mefloquine, primaquine, and quinine
• Medicines to block or prevent stomach acid such as cimetidine (Tagamet), omeprazole (Prilosec), ranitidine (Zantac), and sucralfate (Carafate)
• Medicines to treat low sodium levels such as conivaptan (Vaprisol) and tolvaptan (Samsca)
• Medicines to treat or prevent blood clots such as apixaban (Eliquis), cilostazol (Pletal), clopidogrel (Plavix), dabigatran (Pradaxa), dipyridamole (Persantine), dipyridamole/aspirin (Aggrenox), prasugrel (Effient), rivaroxaban (Xarelto), ticagrelor (Brilinta), vorapaxar (Zontivity), and warfarin (Coumadin)
• Medicines to treat pulmonary hypertension such as macitentan (Opsumit), sildenafil (Revatio), and tadalafil (Adcirca)
• Methotrexate (Otrexup, Rasuvo, Rheumatrex, Trexall)
• Mifepristone (Korlym, Mifeprex)
• Muscle relaxants such as baclofen (Gablofen, Lioresal), carisoprodol (Soma), cyclobenzaprine (Amrix), dantrolene (Dantrium), methocarbamol (Robaxin), and tizanidine (Zanaflex)
• Naloxegol (Movantik)
• Natural remedies such as evening primrose, gotu kola, kava, red yeast rice, St. John's wort, and valerian
• Nausea medicines such as aprepitant (Emend), netupitant/palonosetron (Akynzeo), prochlorperazine (Compro), and promethazine
• Nimodipine (Nymalize)
• Nintedanib (Ofev)
• Orlistat (alli, Xenical)
• Other antiseizure medicines such as carbamazepine (Carbatrol, Epitol, Equetro, Tegretol), ethosuximide (Zarontin), felbamate (Felbatol), methsuximide (Celontin), oxcarbazepine (Trileptal), phenobarbital, tiagabine (Gabitril), topiramate (Qudexy, Topamax, Trokendi), valproic acid (Depacon, Depakene, Depakote), and vigabatrin (Sabril)
• Pain medicines such as codeine, fentanyl (Abstral, Actiq, Duragesic, Fentora, Sublimaze), hydrocodone (Hysingla, Zohydro), hydromorphone (Dilaudid, Exalgo), meperidine (Demerol), methadone (Dolophine, Methadose), morphine (Kadian, MS Contin), oxycodone (OxyContin, Roxicodone), oxymorphone (Opana), tapentadol (Nucynta), and tramadol (ConZip, Ultram)
• Paroxetine (Brisdelle, Paxil, Pexeva)
• Praziquantel (Biltricide)
• Roflumilast (Daliresp)
• Sleeping pills such as butabarbital (Butisol), flurazepam, suvorexant (Belsomra), temazepam (Restoril), triazolam (Halcion), zaleplon (Sonata), and zolpidem (Ambien, Edluar, Intermezzo)
• Stimulants such as amphetamine/dextroamphetamine (Adderall), dexmethylphenidate (Focalin), dextroamphetamine (Dexedrine), methamphetamine (Desoxyn), methylphenidate (Concerta, Daytrana, Metadate, Ritalin), and modafinil (Provigil)
• Tasimelteon (Hetlioz)
• Theophylline
• Thyroid medicines such as levothyroxine (Levo-T, Levothroid, Levoxyl, Synthroid, Unithroid), liothyronine (Cytomel, Triostat), liotrix (Thyrolar), and thyroid USP (Armour Thyroid, Nature-Throid)
• Tofacitinib (Xeljanz)

Do not drink alcohol while taking this medicine unless your healthcare provider approves.

If you are not sure if your medicines might interact, ask your pharmacist or healthcare provider. Keep a list of all your medicines with you. List all the prescription medicines, nonprescription medicines, supplements, natural remedies, and vitamins that you take. Be sure that you tell all healthcare providers who treat you about all the products you are taking.

How should I store this medicine?

Store this medicine at room temperature. Do not refrigerate. Do not let it freeze. Keep the container tightly closed. Protect it from heat, high humidity, and bright light.

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This advisory includes selected information only and may not include all side effects of this medicine or interactions with other medicines. Ask your healthcare provider or pharmacist for more information or if you have any questions.

Ask your pharmacist for the best way to dispose of outdated medicine or medicine you have not used. Do not throw medicine in the trash.

Keep all medicines out of the reach of children.

Do not share medicines with other people.