Phenytoin (brand name Dilantin) is a long-standing anticonvulsant used mainly for tonic-clonic and focal seizures. It’s effective, but tricky: small dose changes can cause big shifts in blood levels. That makes understanding dosing, side effects, and drug interactions essential if you or someone you care for takes it.
Phenytoin stabilizes electrical activity in the brain by blocking sodium channels in neurons. Doctors use it for seizure control and sometimes as an option for status epilepticus after benzodiazepines. You’ll see it as oral tablets, suspension, chewables, and an IV form. Fosphenytoin is a related IV option that’s gentler on veins and often preferred in hospitals.
Start doses vary by age, weight, and other medicines. Because phenytoin follows nonlinear kinetics, plasma levels don’t rise in a straight line with dose increases. That’s why clinicians titrate slowly and check blood concentrations rather than guessing.
Common early side effects include dizziness, nystagmus (eye twitching), unsteady walking, and drowsiness. Serious issues to watch for: rash (can be severe like Stevens–Johnson), liver problems, low blood cell counts, and heart issues if IV phenytoin is pushed too fast. Chronic use can cause gum overgrowth (gingival hyperplasia), excessive hair growth, and bone thinning over time.
Target serum level is usually about 10–20 mcg/mL (total phenytoin). Your provider will order levels, liver tests, and sometimes blood counts. If you’re on long-term therapy, ask about bone health checks and folate — folate supplements may be recommended in some people.
Pregnancy needs extra care. Phenytoin can raise the risk of birth defects (fetal hydantoin syndrome). If you’re planning a pregnancy or become pregnant, talk with your neurologist or OB about risks and safer options. Never stop phenytoin suddenly — that can trigger severe seizures.
Drug interactions are common. Phenytoin is a strong enzyme inducer: it can lower the effectiveness of oral contraceptives, warfarin, and some HIV drugs. Other meds like valproate, fluconazole, or certain antibiotics may raise phenytoin levels and increase toxicity risk. Always check with your prescriber or pharmacist before adding or stopping drugs, including supplements.
Overdose signs include severe drowsiness, slurred speech, low blood pressure, and irregular heart rhythms. For toxicity, medical teams use supportive care; IV fluids and monitoring are key. Activated charcoal may help if the overdose was recent. Hemodialysis is usually not effective because phenytoin binds strongly to proteins.
If you take phenytoin, keep a list of all meds and report new symptoms quickly. Regular blood tests and dental care go a long way toward avoiding problems. Talk openly with your clinician — small adjustments and monitoring keep this effective drug working safely.
May, 29 2025
Dilantin, known also as phenytoin, is a key medication used to control seizures, especially in epilepsy. This article breaks down how it works, tips for safe use, side effects you should watch for, and surprising facts about its long history. We’ll talk about what makes Dilantin stand out and how it’s guided epilepsy treatment for decades. If you or a loved one needs to take this medication, you’ll find the essential info here.