Lidocaine
Xylocaine
Amide local anesthetic / class IB antiarrhythmic
Blocks voltage-gated Na⁺ channels in nerves (LA) and cardiac myocytes (antiarrhythmic).
Indications
- •Local infiltration
- •Spinal/epidural
- •IV regional (Bier block)
- •Topical airway
- •Antiarrhythmic
- •IV infusion for postop pain
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Infiltration | Max 4.5 mg/kg plain; 7 mg/kg with epi | — |
| Topical airway | 4% nebulized 4 mL | — |
| IV bolus antiarrhythmic | 1–1.5 mg/kg IV, repeat 0.5 mg/kg q5–10 min (max 3 mg/kg) | — |
| IV infusion analgesia | 1–2 mg/kg bolus then 1–3 mg/kg/hr | — |
| Bier block | 0.5% 40–50 mL preservative-free | — |
Maximum dose
4.5 mg/kg plain (absolute max 300 mg) · 7 mg/kg with epi (absolute max 500 mg)
Max-dose calculator
single-injection infiltration / blockPlain
300 mg
Capped at absolute max 300 mg
With epinephrine
490 mg
| Concentration | Max volume (plain) | Max volume (with epi) |
|---|---|---|
| 0.5% (5 mg/mL) | 60 mL | 98 mL |
| 1% (10 mg/mL) | 30 mL | 49 mL |
| 1.5% (15 mg/mL) | 20 mL | 32.7 mL |
| 2% (20 mg/mL) | 15 mL | 24.5 mL |
Infiltration/block max only — not the IV antiarrhythmic (≤3 mg/kg) or infusion limits. Education only — confirm against the package insert. Max doses are not additive across agents; account for total LA when mixing.
Pharmacokinetics
Onset 1–5 min (depending on route). Duration 60–120 min. Hepatic CYP metabolism.
Side effects
- !LAST (perioral numbness → tinnitus → seizures → arrhythmia → cardiac arrest)
- !Transient neurologic symptoms (intrathecal lidocaine — back/leg pain hours after spinal)
- !Methemoglobinemia (high doses, prilocaine more so)
Contraindications
- ×Heart block (without pacer) — high-dose IV
- ×Allergy to amide LAs (rare)
Clinical pearls
- ★Add bicarb 1 mEq per 10 mL to alkalinize → faster onset, less burning.
- ★Avoid intrathecal lidocaine if possible — TNS rate up to 14%; bupivacaine better choice.
- ★IV lidocaine infusion: opioid-sparing for laparoscopic surgery.
📊 Related teaching panels
Standalone diagrams matched to this topic.
Other drugs in Local Anesthetics
- Bupivacaine
Voltage-gated Na⁺ channel blocker. Higher protein binding and lipid solubility than lidocaine → longer duration but greater cardiotoxicity.
- Ropivacaine
S-enantiomer of propivacaine. Less lipid-soluble than bupivacaine → less cardiotoxicity but slightly less potency.
Browse all classes: /reference/drugs