Comprehensive medication guide to Phenytoin XR including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
Most insurance plans cover generic Phenytoin XR as a Tier 1 preferred generic with copays typically ranging from $0 to $15.
Estimated Cash Pricing
Generic Phenytoin XR typically costs $18 to $120 for a 30-day supply without insurance, depending on dose and pharmacy.
Medfinder Findability Score
55/100
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Phenytoin XR (extended-release Phenytoin Sodium) is a hydantoin anticonvulsant medication used to treat and prevent seizures. It is FDA-approved for generalized tonic-clonic (grand mal) seizures, complex partial seizures, and the prevention and treatment of seizures during or following neurosurgery. Phenytoin XR is available as a generic and under the brand names Dilantin Kapseals and Phenytek. The typical dose ranges from 200 mg to 600 mg daily, most commonly 300 mg to 400 mg daily taken in one to two divided doses.
Phenytoin XR works by blocking voltage-dependent sodium channels in the brain. This prevents the spread of seizure activity by inhibiting high-frequency repetitive neuronal firing. The extended-release formulation allows for once- or twice-daily dosing and provides steady drug levels throughout the day. Because Phenytoin has a narrow therapeutic index, patients require regular blood level monitoring to maintain levels between 10 and 20 mcg/mL. Patients should not switch between brand and generic versions without physician guidance, as small differences in absorption can significantly affect blood levels.
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100 mg extended-release capsules
200 mg extended-release capsules
300 mg extended-release capsules
50 mg chewable tablets (Dilantin Infatabs)
125 mg/5 mL oral suspension (Dilantin-125) — suspension
Phenytoin XR scores a 55 out of 100 on our findability scale, indicating intermittent availability issues. While extended-release capsules are generally stocked at most pharmacies, periodic supply disruptions have occurred with specific generic manufacturers. The oral suspension formulation (Dilantin-125) has faced more significant shortages, with some manufacturers discontinuing production. If your pharmacy is out of stock, calling around to nearby locations or using Medfinder can help you locate Phenytoin XR quickly.
Phenytoin XR is most commonly prescribed by neurologists and epileptologists who specialize in seizure disorders. However, primary care physicians, family medicine doctors, internal medicine providers, emergency medicine physicians, and neurosurgeons also prescribe it. Telehealth consultations are available for ongoing management and prescription renewals.
No, Phenytoin XR is not a controlled substance and has no DEA scheduling. It does not have abuse potential and can be prescribed with standard prescriptions that allow refills. However, because Phenytoin has a narrow therapeutic index, it requires regular blood level monitoring and careful dose adjustments.
Serious but rare side effects include Stevens-Johnson syndrome, DRESS syndrome, hepatotoxicity, and megaloblastic anemia. Patients of Southeast Asian ancestry should be tested for the HLA-B*1502 allele before starting Phenytoin XR due to increased risk of severe skin reactions.
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Carbamazepine (Tegretol)
Another first-generation anticonvulsant for focal and tonic-clonic seizures with fewer cosmetic side effects but many drug interactions.
Levetiracetam (Keppra)
A newer anticonvulsant with fewer drug interactions and no therapeutic drug monitoring required, commonly used as first-line treatment.
Lamotrigine (Lamictal)
A broad-spectrum anticonvulsant effective for focal and generalized seizures that requires slow titration but is generally well-tolerated.
Valproic Acid (Depakote)
A broad-spectrum anticonvulsant for multiple seizure types, also used for bipolar disorder and migraine prevention.
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Warfarin
moderateAltered anticoagulation effects
Oral contraceptives
moderateReduced effectiveness of birth control
Valproic Acid
moderateDisplaces protein binding and alters Phenytoin levels
Carbamazepine
moderateMutual metabolism changes
Delavirdine
moderateContraindicated due to loss of virologic response
Amiodarone and Fluconazole
moderateCan increase Phenytoin levels
Methotrexate
moderateIncreased toxicity risk
Cyclosporine
moderateReduced Cyclosporine levels
Phenytoin XR remains an important and widely used anticonvulsant despite being one of the older seizure medications available. While newer alternatives like Levetiracetam and Lamotrigine have fewer side effects and drug interactions, Phenytoin XR continues to be effective and affordable for many patients. Generic versions are available for as little as $18 per month with discount coupons. If you're having trouble finding Phenytoin XR in stock at your local pharmacy, Medfinder can help you locate nearby pharmacies that have it available right now.
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