Short answer: Dilantin is a brand name for the anticonvulsant drug phenytoin. Generic phenytoin is the same medicine, just made by different manufacturers. Most people don’t notice a difference, but there are a few practical points to know.
Key points
- Active drug: Both contain phenytoin (usually as the sodium salt). The amount of active drug is the same if the mg strength is the same.
- Brand vs generic: Dilantin is the brand. Generic phenytoin is the same drug made by other companies.
- Formulation differences: Inert ingredients ( fillers, binders, coatings, flavors) can differ between brands and generic versions. The available dosage forms (immediate‑release tablets, capsules, chewables, oral suspension, etc.) may also differ by product.
- Bioequivalence: Generics must meet regulatory standards to be bioequivalent to the brand product. For phenytoin, which has a narrow therapeutic index and nonlinear pharmacokinetics, small differences in absorption can sometimes affect blood levels.
- What this means in practice:
- For most patients, switching from Dilantin to a generic (or between generics) is fine, with similar seizure control and side effects.
- Because phenytoin levels can change with formulation differences, some clinicians monitor blood levels after a switch and may adjust the dose.
- If you’re on a specific release form (for example, an extended-release version), don’t switch to an immediate-release product unless your clinician approves.
Practical guidance
- If a switch occurs, check with your clinician about monitoring phenytoin levels after 1–2 weeks.
- Try to stay on the same product (brand or a specific generic) if you’re doing well, to minimize level fluctuations.
- If you notice more seizures, new or worse side effects, or signs of toxicity after a switch, contact your prescriber promptly.
If you’d like, tell me your current mg dose and which forms you’re using (tablet, capsule, suspension), and I can tailor the explanation more specifically.