How the dose is calculated
Phenytoin's status epilepticus loading dose is 20 mg/kg IV, given at a controlled maximum infusion rate — never as a rapid IV push.
Typical dosing
| Indication | Dose | Max infusion rate | Max total dose |
|---|---|---|---|
| Status epilepticus loading dose | 20 mg/kg IV | 1-3 mg/kg/min (adult max 50 mg/min) | 1500 mg |
Fosphenytoin (a prodrug, dosed in "phenytoin equivalents" — the same mg/kg figure applies) can be infused faster and causes less injection-site irritation, and is preferred where available.
Clinical use
- Second-line agent for status epilepticus after a benzodiazepine (e.g. IV lorazepam/diazepam or buccal/intranasal midazolam) has been given first.
- Requires cardiac monitoring during infusion — rapid administration can cause hypotension and arrhythmia (including bradycardia and heart block).
- Highly irritant to peripheral veins if it extravasates ("purple glove syndrome") — a secure, ideally larger, IV line is preferred.
Frequently asked questions
What is the phenytoin loading dose for status epilepticus?
20 mg/kg IV, given at a controlled rate not exceeding roughly 1-3 mg/kg/min (adult maximum 50 mg/min) — never as a rapid push, and with cardiac monitoring throughout.
Is phenytoin first-line for status epilepticus?
No — a benzodiazepine (IV lorazepam or diazepam, or buccal/intranasal midazolam) is first-line; phenytoin (or fosphenytoin) is the standard second-line agent if seizures continue.
What is "purple glove syndrome"?
A serious local complication of IV phenytoin extravasation causing discoloration, oedema, and pain distal to the injection site, sometimes progressing to tissue necrosis — using a secure, well-flowing IV line reduces this risk.
References
- Glauser T, et al. Evidence-Based Guideline: Treatment of Convulsive Status Epilepticus in Children and Adults. Epilepsy Curr. 2016;16:48-61.