What is the Most Missed Question in Emergency Medicine Exam Prep This Week?
Key takeaway: In IV-accessible status epilepticus, lorazepam is preferred over diazepam due to a longer CNS anticonvulsant effect; when IV access is not available, IM midazolam is preferred over IM diazepam.
Question - Benzodiazepine comparison
A 37-year-old male presents in status epilepticus. Your hospital pharmacy carries both lorazepam and diazepam. In evaluating the two drugs, which factor is TRUE?
Answer Options:
A. Lorazepam has a significantly faster onset of action than diazepam
B. Lorazepam and diazepam have a sublingual formulation.
C. Intramuscular (IM) diazepam is the preferred alternative for emergent seizure control when IV access cannot be achieved.
D. Lorazepam has a longer duration of central nervous system anticonvulsant action than diazepam.
This item is commonly missed because test-takers conflate onset with duration and confuse recommended routes when IV access cannot be obtained. Both diazepam and lorazepam act rapidly IV, but lorazepam’s lower lipophilicity leads to less redistribution and a longer anticonvulsant effect in the CNS, making it preferred when IV access is available.
Guidelines emphasize route-dependent preferences: the American Epilepsy Society (2016) and NICE (2022) support IV lorazepam as first-line with IV access and IM midazolam when IV access is not feasible. IM diazepam is not preferred because of erratic absorption. The keyed answer (D) is correct per these standards.
Why This Emergency Medicine Question Is Often Missed
- Confusion between onset (similar IV) vs. CNS anticonvulsant duration (longer with lorazepam).- Misremembering IM options: IM midazolam—not IM diazepam—is preferred when no IV access.
- Assuming “sublingual” equals an approved, reliable emergent route for both agents (it does not).
What the Distractors Indicate
| Option | What It Tests / Implies | Why It’s Wrong Here |
|---|---|---|
| Lorazepam has a significantly faster onset of action than diazepam | Differentiates onset vs. duration | IV onset is rapid for both; diazepam may be slightly faster, but not "significantly" clinically superior |
| Lorazepam and diazepam have a sublingual formulation | Knowledge of formulations and emergency routes | Diazepam lacks an approved sublingual formulation; sublingual use is not an accepted emergent route for either in status. |
| Intramuscular (IM) diazepam is the preferred alternative for emergent seizure control when IV access cannot be achieved | Route selection without IV access | Guidelines recommend IM midazolam, not IM diazepam, due to more reliable absorption and evidence of efficacy. |
| Lorazepam has a longer duration of central nervous system anticonvulsant action than diazepam | CNS pharmacokinetics | Correct: lorazepam has longer CNS anticonvulsant action due to less redistribution. |
High-Yield Pearl for ABEM Exam Prep
When IV access is available, choose IV lorazepam for longer CNS anticonvulsant effect; without IV, choose IM midazolam—not IM diazepam.
Core Learning Objectives
1. Distinguish onset versus CNS anticonvulsant duration for lorazepam vs. diazepam in status epilepticus.
2. Select the appropriate benzodiazepine and route when IV access is or is not available.
The Exam Trick at Play
This item tests nuanced pharmacokinetics (redistribution vs. half-life) and the evidence-based route preference (IM midazolam over IM diazepam) when IV access is unavailable—common pitfalls under test pressure.
Additional Practice Questions for Status Epilepticus Benzodiazepine Selection
Emergency Medicine Practice Question 1 — No IV access in adult SE
A 62-year-old with generalized convulsive status epilepticus has no IV access. Best immediate benzodiazepine choice?
A. Intranasal diazepam
B. Rectal diazepam gel
C. IM midazolam
D. IM lorazepam
E. IM diazepam
Emergency Medicine Practice Question 2 — Onset vs duration
Which statement best compares IV lorazepam and IV diazepam in status epilepticus?
A. Lorazepam has a much faster onset than diazepam.B. Diazepam has longer CNS anticonvulsant duration than lorazepam.
C. Diazepam has a slightly faster onset, but lorazepam has a longer CNS anticonvulsant effect.
D. Both have prolonged CNS anticonvulsant effects.
E. Both have slow onset IV.
Emergency Medicine Practice Question 3 — Route reliability
Which route-agent pairing is most unreliable for emergent seizure control?
A. IV diazepam
B. IM diazepam
C. IV lorazepam
D. IM midazolam
E. IO lorazepam
Emergency Medicine Practice Question 4 — Adult dosing
Initial adult IV lorazepam dose for convulsive status epilepticus?
A. 0.02 mg/kg (max 2 mg)
B. 0.05 mg/kg (max 3 mg)
C. 0.1 mg/kg (max 4 mg)
D. 0.2 mg/kg (max 10 mg)
E. Fixed 1 mg dose
Emergency Medicine Practice Question 5 — Mechanism of longer CNS effect
What pharmacokinetic property explains lorazepam’s longer anticonvulsant action vs. diazepam?
A. Higher plasma protein binding
B. Lower lipophilicity leading to less redistribution out of the CNS
C. Greater volume of distribution
D. Presence of active metabolites
E. Faster hepatic clearance
Mini Case Discussion Prompt
Compare management pathways for an adult with CSE with and without IV access at arrival, including first-line benzodiazepine choice, dosing, and how pharmacokinetics inform your selection; then discuss what changes, if any, in pediatrics.
Mini-FAQ
- Q: Do the boards expect IM diazepam when no IV is available?A: No. Expect IM midazolam as the preferred route when IV access is not immediately available (AES 2016; NICE 2022).
- Q: Is diazepam’s longer half-life relevant for first-line SE control?
A: Not for acute anticonvulsant effect—diazepam redistributes quickly, shortening its CNS anticonvulsant duration compared with lorazepam.
- Q: Are sublingual preparations appropriate for status epilepticus?
A: No. Sublingual routes are not recommended for emergent control of CSE; IV or IM (midazolam) are preferred.
- Q: If the first benzodiazepine fails, what’s next?
A: After adequate benzodiazepine dosing, proceed to second-line therapy (e.g., levetiracetam, fosphenytoin, or valproate), which have comparable efficacy in benzodiazepine-refractory CSE (ESETT 2019).
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