Phenytoin is an anti-seizure medicine used to control tonic-clonic and focal seizures. It has been around for decades and still works well for many people. This page gives clear, practical facts you need: how it works, common doses, key side effects, and safety tips.
Phenytoin stabilizes overactive brain cells by slowing sodium channels. That reduces seizure spread. Doctors choose phenytoin for status epilepticus in some emergency settings and for long-term control when other drugs aren’t suitable. You may hear the brand name Dilantin, but most prescriptions are for generic phenytoin.
Typical adult oral doses start at 100 mg two or three times a day, then adjust based on response and blood levels. Therapeutic serum levels usually fall between 10–20 mcg/mL. For IV use in emergencies, phenytoin must be given slowly (no faster than 50 mg/min in adults) and diluted properly to avoid heart or blood pressure problems. Loading doses are common when rapid control is needed.
Watch for common side effects: dizziness, unsteady walking, nystagmus (eye movement), and fatigue. Long-term effects include gingival overgrowth (gum swelling), increased facial hair, and bone thinning. Rare but serious reactions include severe skin rashes and liver or blood problems. If you get a rash, fever, or unusual bruising, contact your doctor right away.
Phenytoin interacts with many drugs because it speeds up liver enzymes. That can lower levels of other medicines like warfarin, oral contraceptives, and some antidepressants. Tell your clinician about every medication and supplement you take so they can check for interactions and adjust doses when needed.
Take phenytoin the same way every day: with or without food consistently to keep levels steady. Don’t crush extended-release forms. If you miss a dose, take it as soon as you remember unless it’s almost time for the next dose—then skip the missed one. Avoid sudden stopping; that can cause more seizures. If you need to stop phenytoin, work with your doctor to taper slowly.
Expect regular blood tests. Doctors check phenytoin levels, basic liver tests, and sometimes blood counts. Dental care matters: see your dentist regularly and tell them you’re on phenytoin to help manage gum growth. Women planning pregnancy should discuss risks; phenytoin can raise birth defect risk, so doctors weigh benefits and alternatives carefully.
If you experience severe side effects, fainting, fast heartbeat, chest pain, or breathing trouble after a dose, seek urgent care. For most people, careful monitoring and practical habits make phenytoin safe and effective. Ask your healthcare team any specific questions about dosing, interactions, or monitoring—they know your situation best.
Overdose signs include severe drowsiness, slurred speech, low blood pressure, and breathing problems; emergency care may require activated charcoal or supportive measures. Avoid heavy drinking because alcohol changes phenytoin levels and increases side effects. Children need special dosing and close monitoring. Store tablets at room temperature away from moisture. Keep a list of drugs and wear a medical ID if you have recurrent seizures daily.
Discover everything you need to know about Dilantin, including how it treats epilepsy, what science says about its effectiveness, and tips for managing its side effects. This article breaks down the details about phenytoin in plain language, explores real-life concerns, and shares important facts you won't find on the medication label. Whether you're new to Dilantin or have experience with anti-seizure medicines, you'll find practical guidance and data to help you make informed choices.
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