Dibucaine
Nupercainal
Amide local anesthetic (most potent/toxic) — topical; also a lab reagent
Na⁺-channel blocker; most potent and most toxic LA. Clinically used topically, but best known for the dibucaine-number test of pseudocholinesterase.
Indications
- •Topical (hemorrhoidal/skin) anesthesia
- •Lab: dibucaine number (pseudocholinesterase phenotyping)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Topical | 0.5–1% ointment/cream | — |
Pharmacokinetics
Long-acting; topical use limits systemic exposure.
Side effects
- !High systemic toxicity if absorbed
- !Local irritation
Contraindications
- ×Application to large denuded areas (absorption)
Clinical pearls
- ★DIBUCAINE NUMBER: dibucaine inhibits normal pseudocholinesterase ~80% (number ~80). Atypical homozygotes ~20 → prolonged succinylcholine/mivacurium/ester-LA effect. Heterozygotes ~40–60.
- ★The number is a QUALITATIVE (genotype) test, not a measure of enzyme quantity.
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.
- Chloroprocaine
Na⁺-channel blocker. Extremely rapid plasma-cholinesterase metabolism (half-life seconds) → lowest systemic toxicity of the LAs, ideal for OB epidural top-up.
- 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.
Browse all classes: /reference/drugs
Suggested reading
- •Stoelting & Hines, Pharmacology & Physiology in Anesthetic Practice, 6e
- •FDA package insert
- •ASRA LAST checklist, 2020
