Benzodiazepine
Midazolam
Versed Benzodiazepine — orange ⚠ 1 mg/mL⚠ 5 mg/mL
Pre-op anxiolysis and amnesia; synergistic with opioids for respiratory depression.
Typical adult doses
| Indication | Dose | Onset | Duration |
|---|---|---|---|
| Pre-op anxiolysis / sedation | 0.5–2 mg IV titrated (≈0.01–0.05 mg/kg); less in elderly or with opioids | 1–3 min (peak 3–5) | 30–60 min |
Mechanism
Binds the benzodiazepine site of GABA-A → increases chloride-channel opening frequency.
Key effects
- Anxiolysis, amnesia, sedation
- Mild ↓BP
Watch out for
- Boxed warning: respiratory depression, especially combined with opioids
- Paradoxical agitation and delirium in the elderly
- Prolonged in elderly, obesity, liver/kidney disease (active metabolite)
- Two concentrations exist — read the vial
Reversal
Flumazenil 0.2 mg IV over 15 s, repeat 0.2 mg every 60 s to 1 mg. Shorter-acting than midazolam → resedation. May precipitate seizures (chronic benzodiazepine use, TCA overdose).
Pimp questions
Pimp question 1
Where does flumazenil act?
Answer
It competitively antagonizes the benzodiazepine binding site on the GABA-A receptor.
Pimp question 2
Why does midazolam hurt less on injection than diazepam?
Answer
Its ring is open (water-soluble) at acidic pH in the vial and closes to the lipophilic form at body pH — no propylene glycol needed.