A patient in the ICU has been fitting continuously for 35 minutes despite two doses of IV lorazepam. What is the next appropriate pharmacological step and its mechanism?

• A IV phenobarbitone — positive allosteric modulation of GABA-A, prolongs Cl- channel opening duration
• B IV fosphenytoin — blocks inactivated Na+ channels; mechanism makes it effective in benzodiazepine-refractory status ✓
• C IV levetiracetam — binds SV2A vesicle protein to reduce glutamate exocytosis
• D IV valproate — blocks T-type Ca2+ channels and increases GABA synthesis

Explanation

After failure of two adequate benzodiazepine doses (established status epilepticus), the next step per current protocols is a second-line agent: IV fosphenytoin (or phenytoin), levetiracetam, or valproate. Fosphenytoin is a phosphate ester prodrug of phenytoin, rapidly converted by phosphatases; it blocks voltage-gated sodium channels in the inactivated state, preventing sustained repetitive firing. Among the listed options, fosphenytoin is the traditional second-line agent with the most established status epilepticus evidence when lorazepam fails.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.