Local Anaesthetic (Amide) Pregnancy: Caution — avoid in late pregnancy (methaemoglobinaemia risk); EMLA safe for labour procedures

Prilocaine

Brand names: Citanest, EMLA (with lidocaine)

Adult dose

Dose: Infiltration: 0.5–1%; Nerve block: 1–2%; IV regional anaesthesia (Bier's block): 0.5% 3 mg/kg; EMLA cream: apply 1–5 g under occlusion

Route: Infiltration / Nerve block / IV (Bier's block) / Topical

Frequency: Single dose

Max: 6 mg/kg (plain); 8 mg/kg (with felypressin)

Drug of choice for IV regional anaesthesia (Bier's block) — lowest cardiac toxicity of amide LAs. Metabolised to o-toluidine which causes methaemoglobinaemia at high doses. EMLA = 2.5% lidocaine + 2.5% prilocaine cream.

Paediatric dose

Route:

EMLA cream: apply 1 hour before venepuncture in children ≥1 year. Avoid in neonates and infants <3 months — risk of methaemoglobinaemia. For other routes: seek specialist opinion.

Dose adjustments

Renal

No significant adjustment required.

Hepatic

Caution in hepatic impairment — reduced metabolism.

Clinical pearls

Antidote for methaemoglobinaemia: methylthioninium chloride (methylene blue) 1–2 mg/kg IV over 5 minutes — only use in symptomatic patients (SpO2 falsely low with pulse oximetry)
Drug of choice for Bier's block — low cardiotoxicity means safer if tourniquet deflated prematurely
EMLA cream requires minimum 60 minutes contact time under occlusion for adequate skin anaesthesia

Contraindications

Anaemia
Congenital or idiopathic methaemoglobinaemia
Neonates and infants <3 months (EMLA — methaemoglobinaemia risk)
G6PD deficiency

Side effects

Methaemoglobinaemia (dose-dependent — presents as cyanosis not responding to O2)
LAST (lower risk than bupivacaine)
Hypotension

Interactions

Drugs causing methaemoglobinaemia (sulfonamides, dapsone, nitrates — additive risk)
Oxidising agents

Monitoring

SpO2 (methaemoglobinaemia causes falsely low reading — confirm with co-oximetry)
Clinical cyanosis not responding to O2

Reference: BNFc; BNF 90; BNFc; AAGBI IV Regional Anaesthesia Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Pathways