Lidocaine with phenylephrine

How it works

Lidocaine blocks voltage-gated sodium channels in nerve membranes to prevent impulse conduction, while phenylephrine causes local vasoconstriction that slows systemic absorption of the anaesthetic and reduces local bleeding.

Prescribing in practice

• Avoid injection of vasoconstrictor-containing solutions into or near end-arterial sites such as digits, nose, ears, penis or skin flaps, where vasoconstriction can cause ischaemic necrosis.
• Always aspirate before injecting to avoid inadvertent intravascular administration, and respect the recommended maximum total dose to prevent systemic lidocaine toxicity.
• Use with caution in patients with cardiovascular disease, hyperthyroidism or those taking drugs that potentiate sympathomimetics.

Monitoring

Monitor for early signs of systemic local anaesthetic toxicity such as perioral tingling, tinnitus, agitation or cardiovascular instability, and observe for excessive sympathomimetic effects.

Counselling the patient

• Numbness will wear off gradually; protect the anaesthetised area from heat, biting or injury until sensation returns.
• Report dizziness, palpitations, ringing in the ears or a metallic taste during the procedure immediately.

Evidence & guidelines

Lidocaine with a vasoconstrictor is a long-established standard for infiltration and dental anaesthesia, with use guided by SPC and recognised local anaesthetic safety guidance on maximum doses and toxicity management.