Local anaesthetics (LAs) vary in potency, toxicity, duration of action, stability, water solubility and ability to penetrate mucous membranes. These determine the route of administration.

After most regional LAs maximum arterial plasma concentrations develop within 10-20 minutes, so monitoring of toxic events should take place during the first 30 minutes after injection. Care should be taken to avoid accidental intravascular injection.

LA toxicity usually results from excessively high plasma concentrations. Effects initially include light-headedness, sedation, paraesthesia and twitching. Convulsions can occur in severe reactions. With inadvertent IV injection convulsions and serious cardiac events may occur rapidly particularly with bupivacaine.

Most LAs cause vasodilation and adrenaline (1:200000) may be added which promotes vasoconstriction and prolongs the local activity of the LA. LA with adrenaline combinations should not be used on digits and appendages.

Lidocaine preparations used for local anaesthesia, listed elsewhere in the formulary:

• Instillagel, see section 18.4 Catheter accessories
• Lidocaine 700mg (5% w/w) medicated plaster and Emla Cream see section 10.3.3 Topical analgesia and capsaicin

Lidocaine hydrochloride

• Solution for injection 20mg/2ml (1%) (£0.41 = 1 ampoule)
• Solution for injection 50mg/5ml (1%) (£0.60 = 1 ampoule)
• Solution for injection 100mg/5ml (2%) (£0.60 = 1 ampoule)
• Solution for injection 50mg/10ml (0.5%) (£1.00 = 1 ampoule)

Lidocaine with adrenaline

• Solution for injection 10mg/1ml (1%) with adrenaline 5micrograms/1ml (1 in 200,000) (£1.93 = 20ml vial)
• Dental solution for injection cartridge 44mg in 2.2ml (2%) with adrenaline 27.5 micrograms in 2.2ml (1 in 80,000) (£0.66 = 1 cartridge)
• Injection 200mg (1%) with adrenaline 100 micrograms (1 in 200,000) in 20ml vial preserved
• Injection 400mg (2%) with adrenaline 100 micrograms (1 in 200,000) in 20ml vial preserved

Lidocaine 10%

• Spray sugar free (£6.29 = 50ml bottle)

Lidocaine 5%

• Ointment (£15.00 = 15g)

Tetracaine

• 4% gel 1.5g (£1.08)

Notes

1. Tetracaine gel is indicated prior to venepuncture. After application (together with an occlusive dressing) venepuncture may be carried out after 30 minutes, with anaesthesia lasting 4-6 hours. It is rapidly absorbed from mucous membranes and should never be applied to inflamed, traumatised or highly vascular surfaces. It is not recommended for infants under 1 month or for premature infants.
2. Tetracaine gel is preferred to Emla because it is quicker acting and can be used on infants under 1 year (but over 1 month).

Lidocaine 4% topical solution

• 30ml (unlicensed)

Bupivacaine is the principle LA for spinal anaesthesia. It is often used in lumbar epidural blockade and is particularly suitable for continuous epidural analgesia in labour. It has a longer duration of action compared to other LAs.

Bupivacaine hydrochloride

• 0.125% in 65mL, 250ml
• 0.5% in 4ml (Marcaine heavy)

Bupivacaine with adrenaline

• Injection 25mg (0.5%) with adrenaline 50 micrograms (1 in 200,000) in 10ml ampoule
• Injection 50mg (0.5%) with adrenaline 50 micrograms (1 in 200,000) in 10ml ampoule

Cocaine 10% CD

• Spray

Cocaine 5% with adrenaline 1 in 2000 CD

• Gel

Notes

1. Cocaine solution is used for topical anaesthesia of the nose and Cocaine with adrenaline gel is used for topical anaesthesia for minor cuts. Both are pharmaceutical specials.

Levobupivacaine

• Injection 2.5mg in 1ml (0.25%), 10ml ampoule
• Infusion 2.5mg in 1ml (0.25%), 250ml
• Injection 5mg in 1ml (0.5%), 10ml ampoule
• Infusion 0.125%, 250ml

Levobupivacaine with fentanyl

• 0.1% with 2 micrograms in 1ml fentanyl in 250ml

Mepivacaine hydrochloride

• Injection 30mg in 1ml (3%) 2.2ml cartridge (for podiatry)

Prilocaine

• Injection 50mg (0.5%) 50ml ampoule
• Injection 20mg in 1ml
• Injection 60mg with felypressin 1.04mg cartridge (for dental anaesthesia)

Notes

1. Prilocaine is associated with low toxicity and is the agent of choice for IV regional anaesthesia (e.g. Bier's block).