Chloroprocaine
Nesacaine · Clorotekal
Ester local anesthetic (short-acting)
Na⁺-channel blocker. Extremely rapid plasma-cholinesterase metabolism (half-life seconds) → lowest systemic toxicity of the LAs, ideal for OB epidural top-up.
Indications
- •Epidural (rapid surgical anesthesia, OB stat cesarean top-up)
- •Short spinals (ambulatory)
- •Peripheral blocks / infiltration
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Epidural (surgical) | 2–3% 15–25 mL | — |
| Spinal (ambulatory) | 40–50 mg | — |
Maximum dose
11 mg/kg plain (absolute max 800 mg) · 14 mg/kg with epi (absolute max 1000 mg)
Max-dose calculator
single-injection infiltration / blockPlain
770 mg
With epinephrine
980 mg
| Concentration | Max volume (plain) | Max volume (with epi) |
|---|---|---|
| 1% (10 mg/mL) | 77 mL | 98 mL |
| 2% (20 mg/mL) | 38.5 mL | 49 mL |
| 3% (30 mg/mL) | 25.7 mL | 32.7 mL |
Highest max dose of the injectable LAs due to ultra-rapid ester hydrolysis. Education only — confirm against the package insert. Max doses are not additive across agents; account for total LA when mixing.
Pharmacokinetics
Onset 5–10 min. Duration 30–60 min. Plasma-cholinesterase half-life ~25 sec → minimal LAST risk.
Side effects
- !Back pain (historical high-dose/preservative formulations)
- !Shorter duration
- !Ester allergy
Contraindications
- ×Ester allergy
Clinical pearls
- ★Fastest ester metabolism → safest LA for rapid epidural bolus when LAST risk is a concern (e.g., converting labor epidural for stat cesarean).
- ★Very short duration — a feature for ambulatory spinals, a limit for long cases.
Other drugs in Local Anesthetics
- Lidocaine
Blocks voltage-gated Na⁺ channels in nerves (LA) and cardiac myocytes (antiarrhythmic).
- 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.
- Tetracaine
Blocks voltage-gated Na⁺ channels. Long-acting ester, metabolized by plasma cholinesterase. High potency + toxicity.
- Procaine
Na⁺-channel blocker; prototype ester LA. Plasma-cholinesterase metabolized to PABA.
- Prilocaine
Na⁺-channel blocker. Metabolized to o-toluidine → oxidizes hemoglobin → methemoglobinemia at high doses.
- Levobupivacaine
The S(−)-enantiomer of bupivacaine → similar block with LESS cardiotoxicity + CNS toxicity than racemic bupivacaine.
Suggested reading
- •Stoelting & Hines, Pharmacology & Physiology in Anesthetic Practice, 6e
- •FDA package insert
- •ASRA LAST checklist, 2020
