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Phenytoin: Uses, Dosage, Side Effects, and Drug Interactions
Summary of Key Points
Phenytoin is a prescription medication primarily used to control seizures in conditions such as epilepsy and status epilepticus. It works by stabilizing electrical activity in the brain. Additionally, Phenytoin is sometimes prescribed for managing conditions like trigeminal neuralgia and certain types of pain. Always consult your healthcare provider before starting or adjusting your dose. Our telemedicine providers are available to help manage your treatment.
Names of Medication
US Brand Names: Dilantin, Phenytek
Generic Name: Phenytoin
The generic name refers to the active ingredient in the medication, while the brand name is assigned by the manufacturer. The generic name is listed in parentheses.
Pharmacologic Category
Anticonvulsant
Antiarrhythmic
Phenytoin Dosage
Phenytoin is prescribed for a variety of conditions, and the dosage and frequency depend on the specific condition being treated. Always follow your doctor’s instructions and consult them before making any changes to your dose. You can also reach out to one of our telemedicine providers for personalized guidance.
Phenytoin for Epilepsy
Initial Dose: 100 mg orally three times daily
Maintenance Dose: 300 mg to 400 mg per day, divided into one to three doses
Phenytoin for Seizures
Initial Dose: 100 mg orally three times daily
Maintenance Dose: 300 mg to 400 mg per day, divided into one to three doses
Phenytoin for Status Epilepticus
Loading Dose: 10-15 mg/kg intravenously (IV) at a rate not exceeding 50 mg/min
Maintenance Dose: 100 mg IV every 6-8 hours
Phenytoin for Trigeminal Neuralgia
Initial Dose: 100 mg orally three times daily
Maintenance Dose: Adjust based on response, typically 300-400 mg per day
Phenytoin for Neuropathic Pain
Initial Dose: 100 mg orally three times daily
Maintenance Dose: Adjust based on response, typically 300-400 mg per day
Phenytoin for Cardiac Arrhythmias
Loading Dose: 250 mg IV over 5 minutes
Maintenance Dose: 100 mg orally three times daily
Phenytoin for Post-Traumatic Seizures
Initial Dose: 100 mg orally three times daily
Maintenance Dose: 300-400 mg per day, divided into one to three doses
Phenytoin for Alcohol Withdrawal Seizures
Initial Dose: 100 mg orally three times daily
Maintenance Dose: 300-400 mg per day, divided into one to three doses
Phenytoin for Bipolar Disorder
Initial Dose: 100 mg orally three times daily
Maintenance Dose: Adjust based on response, typically 300-400 mg per day
Phenytoin for Migraine Prophylaxis
Initial Dose: 100 mg orally three times daily
Maintenance Dose: Adjust based on response, typically 300-400 mg per day
Dosage Forms and Strengths
Capsules: 30 mg, 100 mg
Extended-Release Capsules: 100 mg, 200 mg, 300 mg
Chewable Tablets: 50 mg
Oral Suspension: 125 mg/5 mL
Injectable Solution: 50 mg/mL
Administration Instructions for Phenytoin
Phenytoin should be taken exactly as prescribed by your doctor. It can be taken with or without food, but it is important to take it at the same time each day. If using the oral suspension, shake the bottle well before each dose. For the injectable form, a healthcare provider will administer it. Do not stop taking Phenytoin suddenly, as this may worsen seizures. Always consult your healthcare provider before making any changes to your medication regimen.
Contraindications
A contraindication is a specific situation where a medication should not be used because it may be harmful. Phenytoin, like all medications, has certain contraindications that should be carefully considered before starting treatment.
Contraindications for Phenytoin
Hypersensitivity to Phenytoin: If you have a known allergy to Phenytoin or any of its ingredients, you should not take this medication. Allergic reactions can range from mild rashes to severe conditions like anaphylaxis.
Sinus Bradycardia: Phenytoin can slow down the heart rate, so it is contraindicated in people with sinus bradycardia (a condition where the heart beats too slowly) as it may worsen the condition.
Heart Block: Phenytoin can interfere with the electrical signals in the heart, making it unsafe for people with heart block (a condition where the heart’s electrical signals are delayed or blocked).
Adams-Stokes Syndrome: This condition involves sudden, temporary episodes of fainting due to heart rhythm problems. Phenytoin can exacerbate these rhythm issues, making it unsafe for people with this syndrome.
Porphyria: Phenytoin can trigger acute attacks in people with porphyria, a rare genetic disorder that affects the production of heme, a component of hemoglobin.
Phenytoin Drug Interactions
Phenytoin can interact with several other medications, which may either increase the risk of side effects or reduce the effectiveness of one or both drugs. It’s important to inform your healthcare provider about all the medications you are taking, including over-the-counter drugs and supplements.
Medications that Interact with Phenytoin
Warfarin (Coumadin): Phenytoin can decrease the effectiveness of warfarin, a blood thinner, which may increase the risk of blood clots.
Oral Contraceptives (Birth Control Pills): Phenytoin can reduce the effectiveness of hormonal birth control, increasing the risk of unintended pregnancy.
Amiodarone (Pacerone): This heart medication can increase Phenytoin levels in the blood, raising the risk of toxicity.
Fluconazole (Diflucan): This antifungal drug can increase Phenytoin levels, leading to potential side effects like dizziness or confusion.
Carbamazepine (Tegretol): Both Phenytoin and carbamazepine are used to treat seizures, but taking them together can reduce the effectiveness of both medications.
Cimetidine (Tagamet): This medication for heartburn can increase Phenytoin levels, leading to a higher risk of side effects.
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Phenytoin in Pregnancy
Is it Safe to Take Phenytoin During Pregnancy?
Phenytoin, also known as Dilantin, is classified as a Category D medication by the FDA, indicating that there is evidence of potential risk to the fetus. Taking Phenytoin during pregnancy can increase the likelihood of birth defects, including cleft palate, heart abnormalities, and developmental delays. However, in certain situations, the benefits of controlling seizures may outweigh these risks. If you are pregnant or planning to become pregnant, it’s crucial to consult your healthcare provider to explore the safest treatment options. You can also schedule a telemedicine appointment with one of our providers for personalized guidance on Phenytoin use during pregnancy.
Phenytoin While Breastfeeding
Is it Safe to Take Phenytoin While Breastfeeding?
Phenytoin passes into breast milk in small amounts but is generally considered safe for most breastfeeding mothers. However, it’s important to monitor your baby for any signs of side effects, such as excessive drowsiness or feeding difficulties. Always consult your healthcare provider before making decisions about breastfeeding while taking Phenytoin. If you have concerns, you can schedule a telemedicine visit with one of our providers to discuss your options regarding Phenytoin and breastfeeding.
Estimated Cost of Phenytoin Medication
The cost of a 30-day supply of Phenytoin without insurance can vary depending on the pharmacy and location. With a GoodRx coupon, the estimated cost ranges from $10 to $20 for generic Phenytoin. Prices for the brand-name version, Dilantin, may be higher, typically between $50 and $100 for a 30-day supply. Check with your pharmacy for the most accurate pricing on Phenytoin or Dilantin.
Possible Alternatives to Phenytoin
If Phenytoin is not the right medication for you, several alternative treatments are available depending on your condition. Always consult your healthcare provider before making any changes to your treatment plan. You can also schedule a telemedicine visit with one of our providers to discuss these alternatives to Phenytoin.
Epilepsy and Seizures
Alternative Medications: Lamotrigine (Lamictal), Levetiracetam (Keppra), and Valproate (Depakote) are commonly prescribed alternatives to Phenytoin for managing seizures.
Lifestyle Changes: A ketogenic diet, maintaining regular sleep patterns, and managing stress may help reduce seizure frequency in some individuals.
Status Epilepticus
Alternative Medications: Benzodiazepines such as Lorazepam (Ativan) or Diazepam (Valium) are often used to treat status epilepticus.
Trigeminal Neuralgia
Alternative Medications: Carbamazepine (Tegretol) is frequently the first-line treatment for trigeminal neuralgia. Gabapentin (Neurontin) may also be considered.
Other Treatments: In severe cases, surgical options like microvascular decompression may be explored.
Neuropathic Pain
Alternative Medications: Gabapentin (Neurontin) and Pregabalin (Lyrica) are commonly used to manage neuropathic pain.
Lifestyle Changes: Physical therapy and regular exercise may help alleviate symptoms of neuropathic pain.
Cardiac Arrhythmias
Alternative Medications: Beta-blockers such as Metoprolol (Lopressor) or calcium channel blockers like Diltiazem (Cardizem) may be used to manage arrhythmias.
Post-Traumatic Seizures
Alternative Medications: Levetiracetam (Keppra) is often used as an alternative to Phenytoin for preventing seizures following a traumatic brain injury.
Alcohol Withdrawal Seizures
Alternative Medications: Benzodiazepines like Diazepam (Valium) or Lorazepam (Ativan) are typically used to manage seizures related to alcohol withdrawal.
Bipolar Disorder
Alternative Medications: Lithium and Valproate (Depakote) are commonly prescribed to treat bipolar disorder.
Lifestyle Changes: Maintaining regular sleep patterns, managing stress, and engaging in therapy can help manage bipolar disorder.
Migraine Prophylaxis
Alternative Medications: Topiramate (Topamax) and Propranolol (Inderal) are frequently used to prevent migraines.
Lifestyle Changes: Avoiding known triggers, such as specific foods or stress, can help reduce the frequency of migraines.
Recent Updates on Phenytoin Research
Recent studies have focused on the long-term effects of Phenytoin use, particularly its impact on bone health. Research indicates that prolonged use of Phenytoin may lead to decreased bone density, increasing the risk of osteoporosis and fractures. As a result, healthcare providers may recommend regular bone density monitoring and supplementation with calcium and vitamin D for patients on long-term Phenytoin therapy.
Additionally, ongoing research is exploring the potential neuroprotective effects of Phenytoin in conditions such as traumatic brain injury and multiple sclerosis. While these studies are still in the early stages, they suggest that Phenytoin may have broader applications beyond seizure control. If you are interested in learning more about these developments, you can discuss them with one of our providers during a telemedicine visit.
