Generic Dilantin (Phenytoin)

Introduction

Dilantin (phenytoin) is an oral antiepileptic medication supplied as 100 mg tablets. It belongs to the hydantoin class of anticonvulsants and is primarily prescribed to control generalized tonic-clonic (grand mal) seizures and partial seizures in adults. The drug is also indicated for the prevention of seizure recurrence after a first seizure episode. In addition to its approved uses, clinicians sometimes prescribe phenytoin for certain off-label conditions, although such practice must be guided by a qualified health-care professional.

What is Dilantin?

Dilantin is the brand name for the sodium salt of phenytoin, a synthetic aromatic imide discovered in the s and introduced into clinical practice in the s. It is marketed under brand names such as Dilantin, Phenytoin Sodium, and Phenytek. The medication is manufactured by several licensed pharmaceutical companies and distributed worldwide in film-coated 100 mg tablets.

How Dilantin Works

Phenytoin stabilizes neuronal membranes by selectively reducing the influx of sodium ions during the rapid depolarization phase of the action potential. By prolonging the inactive (refractory) state of voltage-gated sodium channels, the drug diminishes the ability of hyperexcitable neurons to fire repetitively. This attenuation of neural firing translates into seizure suppression. Oral absorption is slow and variable; peak plasma concentrations are reached 2-12 hours after ingestion. The drug exhibits a long elimination half-life (approximately 22 hours in adults) and is extensively metabolized by hepatic CYP2C9 and CYP2C19 enzymes.

Conditions Treated with Dilantin

• Generalized tonic-clonic (Grand mal) seizures - Phenytoin reduces the frequency and severity of convulsive episodes by dampening cortical excitability.
• Partial (focal) seizures - The drug limits spread of epileptiform activity from a localized focus to surrounding cortex.
• Seizure prophylaxis after a first unprovoked seizure - Initiating therapy can lower the risk of subsequent seizures in high-risk individuals.

These indications are approved by regulatory agencies such as the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA).

Off-Label and Investigational Uses of Dilantin

• Status epilepticus - Small case series have reported successful adjunctive use of intravenous phenytoin when first-line benzodiazepines are insufficient. Formal guidelines still recommend phenobarbital or levetiracetam as preferred second-line agents.
• Trigeminal neuralgia - Historical reports suggest phenytoin may provide symptomatic relief, but newer monocyclic agents (e.g., carbamazepine) are preferred due to a more favorable safety profile.
• Neonatal seizures - Some neonatal intensive-care units employ phenytoin as a secondary option after phenobarbital, yet recent trials favor newer agents such as levetiracetam.

These applications have not received official approval from the FDA or EMA. Patients should discuss any off-label consideration with a qualified health-care provider, as efficacy and safety have not been established through large-scale regulatory trials.

Is Dilantin the Right Medication for You?

Dilantin is most appropriate for adults with confirmed generalized tonic-clonic or partial seizures who have not responded adequately to first-line agents such as carbamazepine or levetiracetam. It is also useful in individuals who require a medication with a well-characterized therapeutic window and for whom steady-state serum levels can be monitored.

Contraindications include:

• Known hypersensitivity to phenytoin or any hydantoin derivative.
• Significant hepatic impairment (elevated transaminases > 3 × ULN).
• Porphyria or severe cardiac conduction abnormalities (e.g., sinus node dysfunction).

Patients with a history of bone marrow suppression, severe renal disease, or concomitant use of strong CYP2C9 inhibitors should be evaluated carefully before initiating therapy.

Risks, Side Effects, and Interactions

Common

• Gingival hyperplasia - Overgrowth of gum tissue; improves with good oral hygiene and dose adjustment.
• Hirsutism - Excessive facial or body hair, particularly in women.
• Nystagmus - Involuntary eye movements, often dose-related.
• Ataxia - Impaired coordination, usually reversible after dose reduction.

Rare

• Erythema multiforme - Target-like skin lesions; requires immediate discontinuation.
• Stevens-Johnson syndrome (SJS) - Life-threatening mucocutaneous reaction; rare but serious.
• Pseudotumor cerebri - Increased intracranial pressure without mass lesion.

Serious

• Life-threatening arrhythmias - Particularly when administered intravenously too rapidly.
• Severe bone marrow suppression - Aplastic anemia, agranulocytosis, or pancytopenia.
• Hepatotoxicity - Acute hepatitis with jaundice; monitor liver enzymes regularly.

Drug-Drug Interactions

• CYP2C9/CYP2C19 inhibitors (e.g., fluconazole, amiodarone) increase phenytoin levels → risk of toxicity.
• CYP inducers (e.g., carbamazepine, rifampin, St. John’s wort) lower phenytoin concentrations → loss of seizure control.
• Warfarin - Phenytoin can enhance anticoagulant effect; monitor INR closely.
• Oral contraceptives - Phenytoin reduces estrogen efficacy → risk of breakthrough bleeding; alternative contraception may be needed.

Food and Lifestyle Interactions

• Alcohol - Potentiates central nervous system depression; avoid excessive intake.
• High-protein meals - May modestly affect absorption; take tablets with a consistent amount of food or water each day.

Use: Dosing, Missed Dose, Overdose

Standard dosing

• Initial adult dose: 100 mg orally three times daily (total 300 mg/day).
• Maintenance dose: 300-400 mg/day divided into two or three doses, adjusted to maintain a serum concentration of 10-20 µg/mL.
• Dose adjustments are required in the elderly, patients with hepatic dysfunction, or those taking interacting medications.

Missed dose If a dose is missed and it has been less than 12 hours since the scheduled time, take the tablet as soon as remembered. If more than 12 hours have elapsed, skip the missed dose and resume the regular dosing schedule. Do not double-dose to compensate.

Overdose Signs of phenytoin toxicity include nystagmus, ataxia, seizures, respiratory depression, and cardiac arrhythmias. In the event of suspected overdose, seek emergency medical care immediately. Treatment focuses on supportive measures, airway protection, and, if indicated, intravenous administration of lipid emulsion therapy.

Practical precautions

• Swallow tablets whole with a full glass of water; crushing can alter absorption.
• Avoid operating heavy machinery or driving until you know how Dilantin affects you.
• Do not consume grapefruit juice, which can inhibit CYP enzymes and raise plasma levels.

FAQ

• What should I do if I travel internationally with Dilantin? Carry the medication in its original packaging with a copy of the prescription label. Check the destination country's import rules for controlled substances and keep the tablets in your carry-on luggage to avoid temperature extremes.

• Can Dilantin cause a false positive on drug tests? Phenytoin is not typically screened for in standard workplace drug panels, but specialized toxicology tests can detect it. Inform the testing laboratory if you are taking Dilantin to avoid misinterpretation.

• What are the inactive ingredients in the 100 mg tablets? Common excipients include lactose monohydrate, magnesium stearate, microcrystalline cellulose, and colloidal silicon dioxide. Patients with lactose intolerance should verify the specific formulation with the supplier.

• Does Dilantin interact with herbal supplements such as St. John’s wort? Yes. St. John’s wort induces CYP2C9 and CYP2C19, potentially reducing phenytoin concentrations and increasing seizure risk. Discuss any herbal products with your health-care provider before use.

• Is there a specific storage temperature for Dilantin tablets? Store at controlled room temperature (20-25 °C or 68-77 °F). Protect from excess heat, humidity, and direct sunlight to maintain potency.

• How long does it take for Dilantin to reach steady-state levels? Because of its long half-life, steady-state concentrations are typically achieved after 5-7 days of consistent dosing, assuming normal hepatic function.

• Can Dilantin be taken with vitamin D or calcium supplements? Phenytoin can accelerate vitamin D metabolism, leading to decreased calcium absorption and increased risk of osteomalacia. Supplementation may be necessary, but it should be coordinated with laboratory monitoring of bone health.

• Why does my dentist need to know I’m on Dilantin? Phenytoin-induced gingival hyperplasia makes oral hygiene critical. Dental procedures may require prophylactic antibiotics if you have a history of infective endocarditis, and the dentist should be aware of potential drug interactions with local anesthetics containing epinephrine.

• Are there any differences between brand-name Dilantin and generic phenytoin? Both contain the same active ingredient and are required to meet identical bioequivalence standards. Differences may exist in inactive fillers, which can affect tolerability in patients with specific excipient sensitivities.

Glossary

Therapeutic Window

The plasma concentration range in which a drug is effective without causing unacceptable side effects; for phenytoin, this is generally 10-20 µg/mL.

CYP450 Enzymes

A family of liver enzymes (e.g., CYP2C9, CYP2C19) that metabolize many medications; inhibition or induction of these enzymes can alter drug levels.

Gingival Hyperplasia

Excessive growth of gum tissue often caused by chronic exposure to certain antiepileptics, including phenytoin.

Serum Phenytoin Level

The amount of phenytoin measured in the blood; used to guide dose adjustments and avoid toxicity.

Buying Dilantin from Our Online Pharmacy

Patients who encounter limited availability, high out-of-pocket costs, or privacy concerns with conventional pharmacies can obtain Dilantin through our online pharmacy. We source the medication from licensed, audited overseas suppliers who meet stringent quality-assurance standards. This brokerage model enables us to offer the generic formulation at a price that closely reflects the manufacturer’s cost, providing a cost-effective alternative for adults needing long-term seizure control.

All orders are packaged discreetly and shipped with secure tracking. Standard international delivery typically arrives within 7 days with express service, while routine airmail may take up to three weeks, depending on the destination. Because we operate as a pharmacy-broker service, we can navigate complex import regulations while maintaining patient confidentiality. Our dedicated support team verifies each prescription, ensures compliance with local laws, and answers any logistics questions you may have.

Choosing our online pharmacy means you receive a verified, high-quality product without compromising your privacy or budget.

Disclaimer

The information provided about Dilantin is intended for general educational purposes and does not replace professional medical advice. Treatment decisions, including the consideration of off-label applications, must be made under the supervision of a qualified health-care provider. Readers are assumed to be responsible adults capable of making informed health choices. Our online pharmacy makes Dilantin available to individuals who experience limited access through conventional channels or who seek affordable generic alternatives. Always consult your physician before initiating, modifying, or discontinuing any medication.