Phenytoin
Brand Names: Dilantin-125, Dilantin Infatabs, Dilantin
Methodology & AI Transparency ⓘ
Phenytoin Key Takeaways
Translated by Sarah Jenkins (AI RN Plain-English Translator) at a 7th-grade reading level
- 1 What it does: Phenytoin oral suspension is indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures.
- 2 Real-world patient consensus: 77% patient "Worth It" rating across 10 anonymous logs for Phenytoin (RxNorm 1313112).
- 3 Typical cash cost range: 30-day cash pricing ranges from $7.10 on Cost Plus Drugs to $34.50 walk-in retail (NADAC $0.1812/unit).
- 4 Top reported side effects / signs: Leading openFDA/SPL adverse events for Phenytoin: nausea (8.7%), headache (7.2%), dizziness (6.2%).
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Phenytoin Mechanism, CYP450 Pathways & DailyMed Monograph
Phenytoin oral suspension is indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures. Phenytoin oral suspension is indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures. ( 1 )
12.1 Mechanism of Action The precise mechanism by which phenytoin exerts its therapeutic effect has not been established but is thought to involve the voltage-dependent blockade of membrane sodium channels resulting in a reduction in sustained high-frequency neuronal discharges.
Systemic exposure to Phenytoin reflects Estimated 69%–81% oral systemic absorption for Phenytoin absorption kinetics and hepatic oxidation via cyp2c9/cyp2c19 followed by renal and biliary excretion of phenytoin metabolites, sustaining receptor engagement across a Approximately 3–7 hours terminal plasma half-life for Phenytoin half-life window (peak plasma concentration (tmax) reached 1–3 hours post-dose for phenytoin response profile).
Dosing protocols (50 mg/1 Tablet, Chewable or 125 mg/5mL Suspension or 50mg Tablet Chewable or 125mg/5mL Bottle of Oral Suspension or 100mg Capsule) balance efficacy (77.00% patient satisfaction across 10 logs) against nausea (8.7% of reports), headache (7.2% of reports), dizziness (6.2% of reports), with strict avoidance in phenytoin oral suspension is contraindicated in patients with: a history of hypersensitivity to phenytoin, its inactive ingredients, or other hydantoins .; reactions have included angioedema.; a history of prior acute hepatotoxicity attributable to phenytoin ..
Enzyme inducers accelerate biotransformation of Phenytoin, potentially lowering trough levels below therapeutic threshold.
Potent CYP2C9 modulators alter hepatic clearance of Phenytoin, shifting steady-state plasma concentrations.
Standard Adult Titration & Dosages
Absolute & Relative Contraindications
- Phenytoin oral suspension is contraindicated in patients with: A history of hypersensitivity to phenytoin, its inactive ingredients, or other hydantoins .
- Reactions have included angioedema.
- A history of prior acute hepatotoxicity attributable to phenytoin .
Logged Side-Effect Incidence (10 Reports)
Phenytoin Real-World Side Effects: openFDA FAERS vs. Patient Micro-Logs
Peer-Reviewed Human Clinical Trials & Meta-Analyses (Phenytoin)
| Study & Plain-English Finding | Sample (N) | Rigor | Primary Source |
|---|---|---|---|
| Can This Approach Help? Inside the Latest Research on IV Fosphenytoin for Acute Trigeminal Neuralgia: A Multicenter, Randomized, Of 31 participants screened, 22 were randomized; 1 placebo-assigned participant did not meet the NRS ≥5 criterion and was excluded, leaving 21 for analysis (IFT: 11; placebo: 10). Neurology • 2026-06-09 • Phase III Randomized Trial | Multi-cohort | 88/100 | PMID 42096672 ↗ |
Phenytoin Public Price Transparency Ledger
| Dispensing Channel / Benchmark | Verification Source | Reference Cost | Details |
|---|---|---|---|
| Pharmacy Acquisition Cost (CMS NADAC) | CMS Medicaid NADAC Weekly National Survey | $0.1812/unit (~$5.44/30u) | Wholesale baseline |
| Mark Cuban Cost Plus Drugs (Mail-Order Generic) | Public Wholesale Price List (NADAC + 15% + pharmacy fee) | $7.10 / mo | Formulary listing ↗ |
| Average U.S. Walk-In Retail Cash Price | Chain Pharmacy Uninsured Cash Index | $34.50 / mo | Before coupon/insurance |
| Patient-Logged Out-of-Pocket Average | 10 Anonymous DotMD Community Micro-Logs | $8.16 / mo | View logs ↓ |
Phenytoin Federal Verification & Benchmark Summary
| Metric | Verified Benchmark | Source |
|---|---|---|
| Phenytoin RxNorm Concept ID | 1313112 | U.S. National Library of Medicine (RxNorm) |
| CMS NADAC Pharmacy Acquisition Unit Cost | $0.1812 / unit | CMS Medicaid NADAC Weekly Feed |
| Walk-In Chain Pharmacy Cash Average | $34.50 / mo | U.S. Uninsured Retail Cash Index |
| Public Mail-Order Wholesale Benchmark | $7.10 / mo (Cost Plus Drugs) | Mark Cuban Cost Plus Public API |
| Real-World Patient Consensus | 77.00% Worth It (10 anonymous logs) | DotMD Zero-PHI Patient Ledger |
Phenytoin Patient Community, Cohort Filters & Dosage Logs
Federal clinical ledger for Phenytoin integrating DailyMed SPL (2025-05-28), CMS NADAC ($0.1812/unit), and 10 Zero-PHI patient logs.
Share your real dosage and monthly out-of-pocket cost—no account, email, or IP stored.
Filter Phenytoin community threads and patient logs by age, biological sex, dosage, and treatment duration.