Prilocaine

How it works

It reversibly blocks voltage-gated sodium channels in nerve membranes, preventing depolarisation and the propagation of action potentials.

Prescribing in practice

• Excessive doses can cause methaemoglobinaemia through a metabolite, so it is used with particular caution in those susceptible, and methylthioninium chloride is the treatment for significant methaemoglobinaemia.
• As with all local anaesthetics, inadvertent intravascular injection or overdose can cause systemic central nervous system and cardiac toxicity.
• It is often regarded as relatively favourable for intravenous regional anaesthesia, but the maximum safe dose must always be calculated for the individual patient.

Monitoring

Monitor for signs of local anaesthetic systemic toxicity and for cyanosis or low oxygen saturations suggesting methaemoglobinaemia.

Counselling the patient

• Report dizziness, perioral tingling, ringing in the ears or a metallic taste, which can be early signs of toxicity.
• Bluish discolouration of the lips or skin should be reported immediately.

Evidence & guidelines

Its association with methaemoglobinaemia and its use in regional anaesthesia are well documented in standard anaesthetic references and the SPC.