Amide local anesthetic
Lidocaine
Xylocaine Local anesthetic — gray 1% = 10 mg/mL2% = 20 mg/mL
Local anesthetic, induction adjunct and class Ib antiarrhythmic. % × 10 = mg/mL.
Typical adult doses
| Indication | Dose | Onset | Duration |
|---|---|---|---|
| IV before propofol / blunting laryngoscopy | 1–1.5 mg/kg IV (commonly 40–100 mg) | — | — |
| Infiltration max, plain (label, healthy adult) | 4.5 mg/kg, not exceeding 300 mg | — | — |
| Infiltration max, with epinephrine (label) | 7 mg/kg, not exceeding 500 mg | — | — |
Mechanism
Blocks voltage-gated sodium channels → stops impulse conduction.
Key effects
- Local anesthesia; ↓ propofol injection pain; blunts airway reflexes
Watch out for
- Label maximums are not toxicity thresholds — toxicity depends on site (intercostal > epidural > subcutaneous), speed and intravascular injection
- LAST: perioral numbness, metallic taste, tinnitus → agitation, seizures → arrhythmias, cardiovascular collapse — report symptoms immediately
Pimp questions
Pimp question 1
What is the maximum dose of lidocaine?
Answer
Label: 4.5 mg/kg (≤ 300 mg) plain, 7 mg/kg (≤ 500 mg) with epinephrine. These are label limits, not exact toxicity thresholds.
Pimp question 2
How many mg are in 5 mL of 2% lidocaine?
Answer
2% = 20 mg/mL, so 100 mg.