Phenytoin

The recommended dose of phenytoin varies according to individual needs. The recommended starting dose for adults is 100 mg taken 3 times a day. Your doctor will then adjust the dose based on how well it works and is tolerated. The usual adult dose is 300 mg to 400 mg daily taken by mouth in divided doses. An increase to 600 mg taken in divided doses may be needed in some cases. Once the most appropriate dose has been determined for you, and your seizures are controlled, your doctor may suggest that you take the medication in a single daily dose.

The children's dose is based on age and body weight. The recommended starting dose is 5 mg per kilogram of body weight per day, which is then divided into 3 equal doses.

The level of phenytoin in your blood can be checked through laboratory testing. This test helps your doctor determine the dose of phenytoin that best suits you.

Phenytoin may be taken with or after meals. Do not use capsules that are discoloured.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take Phenytoin exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store all forms of Phenytoin at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

In addition to its desired action, this medication may cause some adverse effects, notably: it may cause constipation - to prevent this, drink plenty of water or juice, and eat more dietary fibre; it may cause dizziness - use caution when getting up from a lying or sitting position and use caution if driving; in rare cases it may cause your gums to become swollen or sensitive - see your dentist for your scheduled check-ups; it may cause nausea or, rarely, vomiting; it may cause drowsiness that lasts until the next day - use caution until you know how you will react; it may cause shakiness. Each person may react differently to a treatment. If you think this medication may be causing adverse effects (including those described here, or others), talk to your health care professional. He or she can help you to determine whether or not the medication is the source of the problem.

100 mg
Each hard gelatin capsule with white opaque body and orange opaque cap, imprinted "APO P100" in black ink and filled with white-to-off-white, round biconvex tablets, contains 100 mg phenytoin sodium. Nonmedicinal ingredients: colloidal silicon dioxide, hydroxypropyl methylcellulose, and magnesium stearate; capsule shell: D&C Red No. 28, D&C Yellow No. 10, FD&C Red No. 40, gelatin, and titanium dioxide; pharmaceutical ink: D&C Yellow No. 10 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake, FD&C Red No. 40 Aluminum Lake, iron oxide black, propylene glycol, and shellac.

Do not use phenytoin if you:

• are allergic to phenytoin or any ingredients of the medication
• are allergic to other medications in the class of medications called hydantoins (e.g., fosphenytoin)
• are taking the anti-viral medication delavirdine
• have heart disorders such as slow heart rate, heart block, or abnormal heart rhythms

There may be an interaction between phenytoin and any of the following:

• Abiraterone
• Acetaminophen
• Acetazolamide
• alcohol
• Aliskiren
• Allopurinol
• alpha-blockers (e.g., Alfuzosin, Doxazosin, Tamsulosin)
• Amiodarone
• amphetamines (e.g., Dextroamphetamine, Lisdexamfetamine)
• angiotensin receptor blockers (ARBs; e.g., Candesartan, Irbesartan, Losartan)
• antacids (e.g., aluminum hydroxide, calcium carbonate, magnesium hydroxide)
• antineoplastic agents (chemotherapy; e.g., Carboplatin, Cyclophosphamide, Etoposide, Irinotecan, Vincristine)
• antihistamines (e.g., cetirizine, doxylamine, Diphenhydramine, Hydroxyzine, Loratadine)
• antipsychotics (e.g., Chlorpromazine, Clozapine, Haloperidol, Olanzapine, Quetiapine, Risperidone)
• Apixaban
• Aprepitant
• azelastine
• azole antifungals (e.g., fluconazole, ketoconazole, Voriconazole)
• barbiturates (e.g., butalbital, Phenobarbital)
• benzodiazepines (e.g., Clonazepam, Diazepam, Lorazepam)
• birth control pills
• Bisoprolol
• Bosentan
• brimonidine
• Buprenorphine
• Bupropion
• Buspirone
• cannabis
• calcium channel blockers (e.g., Amlodipine, Diltiazem, Nifedipine, Verapamil)
• calcium supplements
• Carvedilol
• Celecoxib
• chloral hydrate
• chloroquine
• clindamycin
• Cimetidine
• ciprofloxacin
• Cobicistat
• Colchicine
• conivaptan
• corticosteroids (e.g., Dexamethasone, Hydrocortisone, Prednisone)
• Cyclosporine
• dabigatran
• Dantrolene
• Dapsone
• Darifenacin
• Deferasirox
• dexmethylphenidate
• diabetes medications (e.g., chlorpropamide, Glyburide, insulin, Metformin, Rosiglitazone, Saxagliptin)
• Digoxin
• Disopyramide
• disulfiram
• Eplerenone
• Enzalutamide
• estrogens (e.g., conjugated estrogen, Estradiol, ethinyl estradiol)
• Everolimus
• Exemestane
• Flunarizine
• Flutamide
• folic acid
• Furosemide
• Gemfibrozil
• general anesthetics (medications used to put people to sleep before surgery)
• Guanfacine
• Hepatitis C antiviral medications (e.g., asunaprevir, dasabuvir, simeprevir, sofosbuvir)
• hepatitis C antiviral combinations (e.g., ombitasvir - paritaprevir - ritonavir - dasabuvir, ombitasvir - paritaprevir - ritonavir)
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• isoniazid
• ketamine
• Leflunomide
• levodopa
• lidocaine
• lithium
• Loperamide
• Macitentan
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• maraviroc
• Mefloquine
• Meperidine
• Methadone
• Methotrexate
• Methylphenidate
• Metronidazole
• Mexiletine
• mifepristone
• milk thistle
• Mirtazapine
• Modafinil
• Moclobemide
• Montelukast
• multiple vitamin/mineral supplements
• muscle relaxants (e.g., Baclofen, Cyclobenzaprine, methocarbamol, orphenadrine, Tizanidine)
• Nabilone
• Naloxegol
• narcotic pain relievers (e.g., Codeine, Fentanyl, Morphine, Oxycodone)
• nitrates (e.g., isosorbide dinitrate, isosorbide mononitrate)
• Olopatadine
• Ondansetron
• Orlistat
• parasite medications (e.g., albendazole, ivermectin, mebendazole, praziquantel)
• pentamidine
• phosphodiesterase-5 inhibitors (e.g., Sildenafil, Tadalafil, Vardenafil)
• Pimozide
• Piroxicam
• Pramipexole
• prilocaine
• Primaquine
• progestins (e.g., Dienogest, Levonorgestrel, medroxyprogesterone, Norethindrone)
• protein kinase inhibitors (e.g., Dasatinib, imatinib, Nilotinib)
• proton pump inhibitors (e.g., Esomeprazole, Lansoprazole, Omeprazole)
• pyridoxine
• quinidine
• quinine
• Ranitidine
• reserpine
• rifabutin
• rifampin
• rilpivirine
• Riociguat
• Rivaroxaban
• Roflumilast
• Romidepsin
• Ropinirole
• Rotigotine
• salicylates (e.g., acetylsalicylic acid)
• scopolamine
• other seizure medications (e.g., carbamazepine, Clobazam, Lamotrigine, phenobarbital, zonisamide)
• selective serotonin reuptake inhibitors (SSRIs; e.g., Citalopram, Fluoxetine, Paroxetine, Sertraline)
• Sirolimus
• sodium oxybate
• Solifenacin
• "statin" anti-cholesterol medications (e.g., Atorvastatin, Lovastatin, Simvastatin)
• Sucralfate
• sulfadiazine
• sulfonamide antibiotics (e.g., sulfisoxazole, sulfamethoxazole)
• Tacrolimus
• Tapentadol
• tetracyclines (e.g., doxycycline, Minocycline, Tetracycline)
• thalidomide
• theophyllines (e.g., Aminophylline, Oxtriphylline, Theophylline)
• Thyroid replacements (e.g., desiccated thyroid, Levothyroxine)
• Ticagrelor
• Ticlopidine
• Tolterodine
• Tolvaptan
• Tramadol
• Tranylcypromine
• Trazodone
• tretinoin
• tricyclic antidepressants (e.g., Amitriptyline, Clomipramine, Desipramine, Trimipramine)
• Trimethoprim
• Ulipristal
• Venlafaxine
• vitamin D analogues (e.g., alfacalcidol, Calcitriol, cholecalciferol)
• Warfarin
• Zafirlukast
• Zolpidem
• Zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with Phenytoin. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the Nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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 Phenytoin.

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.

Blood counts: Phenytoin can decrease the number of neutrophils (a type of white blood cell that helps fight infection), red blood cells (which carry oxygen), and platelets (which help your blood to clot). Your doctor will do blood tests to monitor this. If you notice any signs of infection (e.g., fever, chills, or sore throat) or unusual bleeding or bruising, contact your doctor immediately.

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 Phenytoin.

Diabetes: Phenytoin can decrease the release of insulin from the pancreas, resulting in higher-than-normal levels of glucose (sugar) in the blood. It may also have an effect on the action of medications used to lower blood sugar for people with diabetes.

If you have diabetes, or are at risk of developing diabetes, discuss with your doctor how Phenytoin may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phenytoin, and whether any special monitoring is needed. It may be necessary to monitor your blood sugar more closely when starting or stopping phenytoin treatment.

If you experience symptoms of increased blood sugar, such as increased urinary frequency, increased thirst, excessive eating, unexplained weight loss, or a fruity breath odour, contact your doctor.

Drowsiness/reduced alertness: Some people who take phenytoin 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 Anaphylaxis (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. These reactions may be more frequent in people of Asian origin, those with immune system problems or those who have a history of similar reactions to other seizure medications.

Lactose intolerance: This capsule form of phenytoin contains lactose. If you have galactose intolerance (galactosemia, glucose-galactose malabsorption, or Lapp lactase deficiency), you should not take the capsule form of Phenytoin.

Liver function: Some people have reported liver problems and, in rare instances, liver failure, 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. If you have decreased liver function or liver disease, discuss with your doctor how Phenytoin may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Phenytoin, and whether any special monitoring is needed.

Osteoporosis: Long term use of anti-seizure medications, including phenytoin, may affect the strength of your bones, because these medications 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 whether you need to take additional vitamin D.

Other medications and alcohol: Many medications and alcoholic beverages 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 Phenytoin, 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 Phenytoin, contact your doctor immediately. You should be closely monitored by your doctor for emotional and behaviour changes while taking Phenytoin.

Pregnancy: When phenytoin is taken during pregnancy, it may cause harm to the developing baby. Phenytoin should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Phenytoin, contact your doctor immediately.

Breast-feeding: Phenytoin 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.

Seniors: People over the age of 65 are more likely to experience side effects of taking phenytoin. Doses for seniors should generally be lower and increase more slowly than for other adults.

This medication is typically used 3 times a day. However, your pharmacist may have suggested a different schedule that is more appropriate for you. The capsule of this medication should not be opened, crushed or chewed. It is not advisable to stop using this product suddenly, particularly if you have been on it for several weeks. If you are considering stopping the medication, talk to your pharmacist first. It must be used regularly and continuously to maintain its beneficial effects. Be sure to keep an adequate supply on hand. If you forget a dose, take it as soon as you remember -- unless it is almost time for your next dose. In that case, skip the missed dose. Do not double the next dose to catch up. Consuming alcohol may intensify the effect of this product. If you choose to drink alcohol, do so in moderation. Talk to your health care professional to find out exactly how much alcohol you can drink.