Dilantin (phenytoin) is an antiepileptic drug (AED) primarily indicated for the prevention and control of focal (partial) seizures and generalized tonic‑clonic seizures. It is also used acutely in the hospital setting for status epilepticus, often given intravenously (or as fosphenytoin, a related prodrug). By stabilizing neuronal membranes and limiting repetitive firing through voltage‑gated sodium channel modulation, Dilantin helps reduce seizure propagation in susceptible brain networks.
Beyond epilepsy, phenytoin has historically been used off‑label in select neuropathic pain conditions and certain cardiac arrhythmias, though these uses are less common today given newer options. In epilepsy care, Dilantin is often considered when newer agents are ineffective, intolerable, or unaffordable. Some people remain on Dilantin for years with reliable seizure control, while others transition to modern AEDs based on side‑effect profiles, comorbidities, pregnancy plans, or interaction considerations.
A hallmark of Dilantin therapy is individualized dosing guided by serum levels and clinical response. Because its pharmacokinetics are non‑linear, small dose changes can produce large shifts in blood levels and clinical effects. Close follow‑up, level monitoring (often targeting 10–20 mcg/mL total phenytoin), and consistent adherence are critical to minimizing breakthrough seizures and avoiding toxicity. For many patients, it remains a valuable, time‑tested option when thoughtfully managed.
Forms: Dilantin is available as extended‑release (ER) capsules, chewable tablets, and an oral suspension; in acute care, IV phenytoin or IV fosphenytoin may be used. Do not change between formulations or brands without clinician guidance—bioavailability differences, even among generics, may affect serum levels and seizure control. Many clinicians recommend sticking to one manufacturer once stable.
Adults (maintenance): Typical total daily dose is 300–400 mg/day, commonly divided (e.g., 100 mg three times daily) or once daily with ER capsules if tolerated. Some patients require lower or higher doses depending on metabolism, interacting medications, age, weight, and comorbidities. Because Dilantin exhibits Michaelis–Menten (saturable) pharmacokinetics, small dose increases (e.g., 30–50 mg/day) may be safer than large jumps to avoid sudden toxicity.
Loading dose (acute or new starts): A common loading regimen is 15–20 mg/kg total (oral or IV), sometimes followed by supplemental loading to rapidly achieve therapeutic levels. Hospitals often use IV fosphenytoin due to improved infusion tolerability. Oral loading can be split into divided doses over several hours to reduce gastrointestinal side effects.
Pediatrics: Dosing is weight‑based (commonly 4–8 mg/kg/day in divided doses for maintenance), titrated to effect and serum levels. Pediatric pharmacokinetics differ, and levels plus clinical observation guide adjustments. Always follow pediatric neurology guidance for age‑appropriate dosing and monitoring.
Monitoring: Routine phenytoin levels are often checked 5–7 days after dose changes (steady state) and periodically thereafter. Target total serum concentrations are generally 10–20 mcg/mL; free phenytoin (unbound) is sometimes measured, especially in hypoalbuminemia, renal disease, pregnancy, or with interacting drugs that alter protein binding. Liver function, complete blood count, vitamin D status, and bone health may also be monitored over time.
Administration tips: Take Dilantin consistently in relation to meals. For oral suspension, gently shake before dosing and use a calibrated measuring device. Separate from enteral tube feeds and high‑protein formulas when possible; feeds can bind phenytoin and reduce absorption—many clinicians recommend holding tube feeds 1–2 hours before and after Dilantin doses and flushing the tube well. Antacids or calcium‑rich products can impair absorption; spacing doses by a couple of hours may help.
Do not abruptly stop Dilantin without medical guidance. Sudden withdrawal can precipitate seizures or status epilepticus. If you and your clinician decide to change therapies, a gradual cross‑taper is typical to maintain seizure protection.
Narrow therapeutic index: Dilantin has a relatively tight therapeutic window. Over‑ or under‑dosing may quickly lead to toxicity or breakthrough seizures. Because metabolism can become saturated, seemingly small dose changes may disproportionately affect levels; careful titration and laboratory monitoring are key.
Dermatologic reactions: Phenytoin can cause rash ranging from mild to life‑threatening. Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but medical emergencies. Risk is higher in carriers of HLA‑B*1502, primarily among individuals of Southeast Asian, Chinese, and Indian ancestry; genetic screening may be considered before initiation in at‑risk populations. Any widespread rash, blistering, mucosal lesions, or systemic symptoms warrant urgent evaluation.
Hematologic/hepatic effects: Rare blood dyscrasias (e.g., agranulocytosis, aplastic anemia) and hepatic injury can occur. Report fever, sore throat, unusual bruising or bleeding, dark urine, jaundice, or persistent fatigue. Periodic liver tests and blood counts may be advised during long‑term therapy.
CNS and gait effects: Dose‑related neurologic side effects include dizziness, nystagmus, ataxia (unsteady gait), tremor, slurred speech, and cognitive slowing. These often signal high serum levels. If you experience new coordination problems or visual blurring, contact your clinician—dose adjustments may be needed.
Long‑term effects: Gingival hyperplasia (gum overgrowth) is relatively common, especially with poor dental hygiene. Rigorous oral care, regular dental visits, and folate adequacy may help. Other chronic effects can include hirsutism, acne, peripheral neuropathy, osteopenia/osteoporosis (due to vitamin D metabolism), and folate deficiency. Calcium/vitamin D supplementation and bone‑density monitoring are often recommended for long‑term users.
Mental health: Like other antiepileptics, Dilantin carries a small but notable risk of mood changes or suicidal ideation. Promptly report new or worsening depression, anxiety, irritability, or unusual behavior. Clinicians balance these risks against the benefits of seizure control.
Pregnancy and fertility: Phenytoin is teratogenic. Exposure during pregnancy can increase the risk of congenital anomalies (e.g., craniofacial differences, limb defects, cardiac anomalies), sometimes called “fetal hydantoin syndrome.” Nonetheless, uncontrolled seizures also pose dangers to mother and fetus. Preconception planning with a neurologist and obstetric specialist is vital; folic acid supplementation (often in higher doses) is typically recommended. Phenytoin clearance may increase in pregnancy, necessitating level‑guided dose adjustments. Phenytoin reduces the efficacy of many hormonal contraceptives—use non‑hormonal or higher‑dose methods per clinician guidance.
Driving and safety: Follow local laws on driving after seizures. Many jurisdictions require a seizure‑free period before resuming driving. Until you know how Dilantin affects you, avoid activities that demand full alertness such as operating heavy machinery or climbing to heights.
Do not switch formulations or stop therapy abruptly without medical advice. Notify all healthcare providers, including dentists and pharmacists, that you take phenytoin to prevent interactions and ensure coordinated care.
Do not use Dilantin if you have a known hypersensitivity to phenytoin, other hydantoins, or any component of the formulation. Patients with a history of severe cutaneous adverse reactions (SJS/TEN) from phenytoin must not be re‑exposed. Genetic risk factors (e.g., HLA‑B*1502) may influence decision‑making in certain populations.
Cardiac conduction issues: IV phenytoin is contraindicated in patients with sinus bradycardia, sinoatrial block, second‑ or third‑degree AV block, and in some atrial arrhythmias due to the risk of worsening conduction abnormalities and hypotension. If IV therapy is needed, clinicians often favor fosphenytoin for improved infusion tolerability and monitor ECG and blood pressure closely.
Use caution or alternative therapy in significant hepatic impairment, porphyria, and in frail older adults prone to falls and polypharmacy. Your clinician will evaluate risk‑benefit considering seizure type, comorbidities, and available alternatives.
Common dose‑related: Drowsiness, dizziness, nystagmus (eye movements), blurred vision, ataxia, slurred speech, and cognitive slowing are frequent when levels are high or rising. Mild nausea, constipation, and anorexia can occur. Many of these improve with dose adjustments or as levels stabilize.
Dermatologic/oral: Rash, pruritus, acne, hirsutism, and gingival hyperplasia (overgrowth of gum tissue) are well‑recognized. Meticulous dental hygiene, regular cleanings, and folate sufficiency may mitigate gum changes. Any severe or spreading rash, mucosal involvement, or systemic symptoms require urgent medical attention.
Metabolic/bone: Long‑term use may contribute to vitamin D deficiency, osteopenia, and osteoporosis. Prophylactic calcium and vitamin D are often advised, along with weight‑bearing exercise and periodic bone‑density screening in those on chronic therapy.
Hepatic/hematologic: Elevated liver enzymes, hepatitis, and rare blood dyscrasias (e.g., leukopenia, thrombocytopenia, aplastic anemia) have been reported. Watch for jaundice, dark urine, easy bruising, or persistent infections.
Idiosyncratic severe reactions: Drug reaction with eosinophilia and systemic symptoms (DRESS), SJS/TEN, and anaphylaxis are rare but serious. Immediate medical care is essential if fever, facial swelling, lymphadenopathy, widespread rash, or organ dysfunction develops.
IV‑related reactions: Rapid IV infusion can cause hypotension and cardiac arrhythmias; infusion rates are typically limited (e.g., ≤50 mg/min in adults) with blood pressure and ECG monitoring. Purple glove syndrome, a painful limb complication due to tissue irritation/extravasation, can occur with IV phenytoin; fosphenytoin reduces this risk but monitoring remains essential.
This is not a complete list. Side effects vary by individual, dose, formulation, and co‑medications. Report new or concerning symptoms to your healthcare team promptly.
Phenytoin is both a substrate and a potent inducer of multiple hepatic enzymes (notably CYP2C9, CYP2C19, and CYP3A4) and UGT pathways. This means many drugs can raise or lower phenytoin levels, and phenytoin can reduce the effectiveness of other medicines by speeding their breakdown. Interactions can be clinically significant; always review your full medication list, including over‑the‑counter products and supplements, with your clinician and pharmacist.
Drugs that may increase phenytoin levels (toxicity risk): Amiodarone, azole antifungals (e.g., fluconazole, voriconazole), isoniazid, chloramphenicol, cimetidine, some SSRIs, and valproic acid (which can also increase free/unbound phenytoin). Symptoms of high levels include nystagmus, ataxia, slurred speech, and confusion.
Drugs that may decrease phenytoin levels (breakthrough seizure risk): Certain chemotherapy agents, enteral feeds (via reduced absorption), antacids/calcium products when co‑administered, and chronic alcohol use. Carbamazepine, phenobarbital, and primidone can also influence levels through enzyme induction.
Drugs whose levels/effects may be reduced by phenytoin: Combined oral contraceptives and many progestin‑only pills (risk of contraceptive failure), anticoagulants such as apixaban/rivaroxaban (reduced efficacy), some statins, many antivirals (including HIV therapies), doxycycline, antifungals, and immunosuppressants (e.g., tacrolimus). Alternative methods or dose adjustments may be required; clinicians often favor non‑hormonal contraception or long‑acting reversible contraception to avoid failure.
Warfarin and phenytoin have complex bidirectional interactions affecting INR and phenytoin levels; close monitoring is necessary when either drug is started, stopped, or adjusted. Folic acid can modestly lower phenytoin levels; supplementation should be coordinated with your clinician, especially in pregnancy planning.
Alcohol may alter phenytoin metabolism—chronic use can induce enzymes (lowering levels), while acute ingestion can inhibit metabolism (raising levels). Consistency with caffeine and nicotine may also help minimize variability in seizure threshold for some people.
Food and enteral nutrition: High‑protein tube feeds and binding in feeding systems can significantly impede absorption of oral suspension; schedule separation and flush protocols can help. If seizures worsen after starting tube feeds, ask your care team to reassess timing and levels.
If you miss a dose of Dilantin, take it as soon as you remember unless it is almost time for your next dose. If it is close to the next scheduled dose, skip the missed dose and resume your regular schedule. Do not double up to “catch up,” as that may increase toxicity risk due to phenytoin’s non‑linear kinetics.
If you miss more than one dose or have a seizure after a missed dose, contact your clinician. They may recommend checking a level or providing short‑term guidance. For extended‑release capsules, follow your prescriber’s exact instructions; timing consistency is important for steady absorption.
Set reminders, use a pill organizer, and keep a medication log to support adherence. For people with complex regimens, pharmacy blister‑packs or synchronized refills can reduce missed doses and refill gaps.
Phenytoin overdose can be dangerous. Signs and symptoms may include profound dizziness, nystagmus, severe ataxia (staggering), slurred speech, confusion, lethargy, vomiting, hypotension, bradycardia, respiratory depression, and coma. IV phenytoin overdosing or rapid infusion increases the risk of cardiac arrhythmias and cardiovascular collapse.
If an overdose is suspected, call emergency services or poison control immediately. Do not induce vomiting. In the emergency department, clinicians provide supportive care, monitor cardiac status, consider activated charcoal for recent large ingestions, and manage complications such as hypotension or seizures. Because phenytoin is highly protein‑bound and distributes into tissues, dialysis is generally not effective; management focuses on supportive measures and time for redistribution and metabolism.
After recovery, your care team will re‑evaluate dosing, adherence aids, and potential interactions that may have contributed to elevated levels. Medical identification jewelry or a smartphone medical ID can help first responders identify your medication in an emergency.
Store Dilantin at controlled room temperature (typically 20–25°C or 68–77°F), away from excessive heat, moisture, and direct light. Keep in the original container with the lid tightly closed. Do not store in the bathroom. For the oral suspension, gently shake before measuring; use a proper dosing syringe or cup for accuracy.
Keep medication out of reach of children and pets. Do not use beyond the expiration date. If your medication appears discolored, clumped, or otherwise altered, consult your pharmacist. Ask your pharmacist about safe disposal options for expired or unused medication; many communities offer take‑back programs.
In the United States, Dilantin (phenytoin) is a prescription‑only medicine. Federal and state laws require that a licensed clinician evaluate you and determine that Dilantin is appropriate before it can be dispensed by a pharmacy. This protects patients by ensuring the right drug, dose, monitoring plan, and follow‑up—especially vital for a medication with a narrow therapeutic index and numerous interactions.
Physician House Calls of Kansas offers a legal and structured pathway for eligible patients to access Dilantin without bringing a pre‑existing paper prescription. A licensed provider visits you at home (or via telehealth if appropriate), reviews your medical history, performs an exam, and determines whether Dilantin fits your seizure type and overall health plan. When clinically appropriate, the provider issues a valid prescription and coordinates with a partner pharmacy for dispensing or delivery. In some cases, in‑office or point‑of‑care dispensing may be available under state law. This means you receive full, compliant medical evaluation and rapid access—without the burden of arranging a separate clinic visit solely to obtain a written script.
What this is not: It is not “no‑prescription” sales. Any legitimate source in the U.S. requires clinician involvement and a valid prescription. Services that ship prescription drugs without medical evaluation or outside licensed channels can be unsafe and unlawful. Physician House Calls of Kansas streamlines care while staying firmly within legal and clinical standards.
What to expect from a house‑call seizure consultation: The clinician will confirm your seizure diagnosis, review prior imaging and EEGs if available, assess current and past antiepileptic medications, discuss adherence and side effects, screen for interaction risks (contraceptives, anticoagulants, antifungals, antivirals, tube feeds, supplements), and order baseline labs if needed (including phenytoin levels if already taking it). They will also review safety topics like driving restrictions, pregnancy planning, bone health, and dental hygiene. Together, you’ll decide on a treatment plan, which may include Dilantin or an alternative AED better suited to your profile.
After initiation or continuation, the provider can arrange follow‑up blood‑level checks, refill synchronization, and education on missed‑dose handling, overdose recognition, and interaction avoidance. If your levels fluctuate or you experience side effects, your care team can adjust dosing or transition you to a different antiepileptic in a controlled, stepwise manner.
If you are experiencing medication access barriers—transportation, mobility limitations, caregiver constraints, or rural residence—house‑call care can bridge the gap. Reach out to Physician House Calls of Kansas to request an evaluation and learn whether their care model suits your needs. All dispensing occurs through licensed channels and in accordance with U.S. law, prioritizing your safety and continuity of care.
Bottom line on access: To obtain Dilantin legally and safely in the U.S., you need a licensed clinician’s evaluation and prescription. Physician House Calls of Kansas provides that evaluation at your doorstep and coordinates streamlined dispensing, so you can start or continue seizure therapy without making a separate trip just to pick up a written prescription.
Dilantin is an antiseizure (antiepileptic) medication that stabilizes brain activity to prevent seizures. It is commonly used for focal (partial) seizures and generalized tonic-clonic seizures, and intravenously for status epilepticus. It is generally not effective for absence seizures and can worsen them.
Dilantin blocks voltage-gated sodium channels, reducing rapid, repetitive firing of neurons. This “membrane-stabilizing” effect helps prevent seizure activity from starting and spreading.
Adults with focal or generalized tonic-clonic seizures may benefit, especially when cost or access to newer drugs is an issue. People with a history of severe skin reactions (SJS/TEN), significant liver disease, certain heart rhythm problems, or known HLA-B*1502 positivity (in some Asian populations) should generally avoid it. It may not be a good first choice for women of childbearing potential due to teratogenic risk and birth control interactions.
It is available as capsules, chewable tablets, and oral suspension, and can be given intravenously in emergencies. If you use a feeding tube, phenytoin can bind to enteral nutrition; separating tube feeds by 1–2 hours before and after dosing and flushing the tube can help absorption.
Most adults target a total phenytoin level of 10–20 mcg/mL (free level 1–2 mcg/mL). The “right” level is individualized based on seizure control and side effects, and free levels are more informative when albumin is low or kidney failure is present.
Phenytoin has nonlinear (Michaelis–Menten) metabolism, so a small increase in dose can disproportionately raise blood levels once enzymes are saturated. That’s why careful, small dose adjustments and periodic blood level checks are important.
Dose-related effects include dizziness, nystagmus (eye twitching), blurred or double vision, unsteady gait, and slurred speech. With long-term use, gum overgrowth, acne, unwanted hair growth, folate deficiency, peripheral neuropathy, and bone thinning can occur. Many effects improve by slightly lowering the dose if levels are high.
Rash with blistering or mucosal involvement (possible Stevens–Johnson syndrome/TEN), fever with swollen lymph nodes or organ involvement (DRESS), severe liver problems, low blood counts, or thoughts of self-harm require immediate care. Rapid IV infusion can cause arrhythmias and low blood pressure.
Yes. Dilantin is a strong enzyme inducer and can lower the effectiveness of oral contraceptives, anticoagulants, steroids, many antivirals, and other drugs. Medicines that inhibit or induce liver enzymes can raise or lower phenytoin levels. Always check interactions; using nonhormonal contraception or backup methods is often recommended.
Alcohol can affect seizure risk and phenytoin metabolism. Acute drinking may raise phenytoin levels, while chronic heavy use can lower them. If you drink, do so moderately and consistently, and discuss it with your clinician.
Take it as soon as you remember unless it’s close to the next dose. Do not double up. Missing doses can increase seizure risk; set reminders to help maintain steady levels.
Levels are typically checked after dose changes, if seizures or side effects occur, and periodically once stable. Monitoring may include phenytoin level (total and sometimes free), liver enzymes, complete blood count, vitamin D, and bone health over time.
Phenytoin carries a risk of birth defects and pregnancy complications; preconception counseling, folic acid supplementation, and close monitoring are important. During pregnancy, levels often fall, and doses may need adjustment. Breastfeeding is generally considered compatible, as milk transfer is low; monitor the infant for sedation or poor feeding.
Yes. It can decrease vitamin D, leading to bone loss over time, and cause gingival overgrowth. Good oral hygiene, regular dental care, and adequate calcium/vitamin D intake help reduce risks; bone density assessment may be considered for long-term users.
Stopping abruptly can trigger seizures or status epilepticus. Tapering slowly under medical supervision is the norm unless a severe reaction necessitates rapid discontinuation.
Seizure control and side effects such as dizziness or blurred vision can impair driving. Follow local laws on driving after seizures, and avoid hazardous activities during medication changes or if you feel impaired.
IV phenytoin must be infused slowly due to risks of hypotension and arrhythmias; continuous cardiac monitoring is used. Fosphenytoin, a related prodrug, is often preferred IV because it can be given faster with fewer infusion-site problems, including lower risk of “purple glove syndrome.”
People of Han Chinese, Thai, Filipino, and some other Southeast Asian ancestries are at higher risk for SJS/TEN if they carry HLA-B*1502. Genetic screening may be considered before starting aromatic antiseizure drugs, including phenytoin, in at-risk groups.
Fosphenytoin is a prodrug converted to phenytoin in the body. It can be infused faster with fewer infusion reactions and less risk of tissue injury, making it preferred for IV use. For maintenance therapy, both ultimately provide phenytoin; oral Dilantin is typically used for chronic dosing.
Both are effective for focal and generalized tonic-clonic seizures. Carbamazepine may be better tolerated long term and is favored for trigeminal neuralgia, while Dilantin is often used when rapid loading is needed or cost is critical. Both are enzyme inducers with multiple interactions and can cause rash; HLA-B*1502 screening is relevant for both in certain populations.
Levetiracetam has minimal drug–drug interactions and requires no blood level monitoring, making it convenient. Dilantin can be equally effective but needs monitoring and has many interactions and cosmetic side effects. Behavioral issues (irritability, mood changes) are more common with levetiracetam; gum overgrowth and bone effects are concerns with Dilantin.
Valproate is broad-spectrum and covers generalized epilepsies (including absence and myoclonic), which Dilantin does not. Valproate is generally avoided in women who might become pregnant due to high teratogenic risk and potential cognitive effects on offspring. Dilantin may be preferred for focal seizures when rapid loading is needed, but it also has teratogenic risk and interactions.
Lamotrigine is often better tolerated long term with fewer cognitive and cosmetic effects and has antidepressant properties. It requires a slow titration to minimize rash risk. Dilantin works quickly with loading but has more interactions and long-term adverse effects like gingival hyperplasia and bone loss.
Oxcarbazepine has fewer enzyme-inducing effects than Dilantin and fewer interactions overall, though it can lower sodium (hyponatremia). Dilantin strongly induces liver enzymes, affecting many medicines and hormonal contraception. Both can cause dizziness and double vision; rash risk exists with both.
Topiramate can cause cognitive slowing, word-finding difficulties, and weight loss; it can also increase kidney stone risk. Dilantin often causes ataxia, vision issues, and cosmetic side effects, with long-term bone and gum effects. Choice depends on seizure type, comorbidities, and side-effect priorities.
Both are older enzyme inducers. Phenobarbital can be very sedating with cognitive/mood effects and dependence potential; it’s still used where cost and availability are key. Dilantin generally causes less sedation but requires monitoring, has cosmetic effects, and can cause serious rashes.
Both act on sodium channels, but lacosamide enhances slow inactivation, while Dilantin blocks fast inactivation. Lacosamide has fewer interactions but can prolong PR interval and cause dizziness. Dilantin has more interactions and cosmetic effects; ECG monitoring is more relevant with lacosamide in patients with conduction disease.
No. Dilantin is a primary antiseizure drug for focal and generalized tonic-clonic seizures. Gabapentin is weaker for seizures and is mainly used for neuropathic pain; it has few interactions but can cause sedation and weight gain. For epilepsy control, Dilantin is generally more potent.
Zonisamide is once-daily in many patients, covers focal seizures, and may aid weight loss but can cause kidney stones and is contraindicated in sulfa allergy. Dilantin requires level monitoring and has more interactions and cosmetic effects. Zonisamide is not ideal for patients with significant renal impairment.
Primidone is used more for essential tremor (metabolized to phenobarbital) and less commonly for seizures today due to sedation and cognitive effects. Dilantin remains a seizure-focused medication with IV options for emergencies. Both are enzyme inducers with interaction potential.
Clobazam is a benzodiazepine used as add-on therapy, especially in Lennox–Gastaut syndrome, with sedation and tolerance as limits. Dilantin is used as monotherapy or adjunct for focal and tonic-clonic seizures. Clobazam has fewer enzyme-inducing effects; Dilantin requires level monitoring and has notable long-term adverse effects.
Both are effective IV options after benzodiazepines. Fosphenytoin/phenytoin is often used early due to rapid sodium-channel blockade; valproate is an alternative with fewer cardiovascular infusion risks and broad-spectrum coverage. Choice depends on patient factors (cardiac risk, liver disease, pregnancy potential, drug interactions).