Lidocaine

This article is a stub.

Lidocaine
Other names	Lignocaine, Xylocaine
Formulations	1% (10mg/mL), 2% (20mg/mL)
Drug class	Amino amide local anaesthetic
Maximum dose	4.5 mg/kg with plain lidocaine 7 mg/kg with adrenaline Note max dose varies between use cases, e.g. intercostal block safe dose is 10 times less.
Onset of action	Infiltration and minor nerve: 1-2 mins. Intra-articular: 5-10 mins Major nerve blocks:15-30 mins
Duration of action	Infiltration and minor nerve: 1.5 - 2 hours Intra-articular: 30-60 mins post washout Major nerve blocks: 1.5 - 3 hours Duration longer with adrenaline.
Chemical structure	2‐(diethylamino)‐N‐(2,6‐ dimethylphenyl) acetamide hydrochloride monohydrate

Lidocaine was the first clinically used amide local anesthetic in 1948. It is widely used because of its potency; rapid onset; tissue penetration; and effectiveness in infiltration, peripheral nerve block, and both epidural and spinal blocks. In peripheral nerve blockage 1-1.5% is sufficient to produce a motor blockade, while for epidural and spinal blocks higher strengths are used.

Pharmacology

Main article: Local Anaesthetic Pharmacology

Chemical Structure

Buffered Lidocaine

Main article: Buffered Local Anaesthetic

Formulations

Lidocaine Cream

Lidocaine cream is not readily available in New Zealand and is not subsidised. It has to be ordered over the internet.

• Haim International for 10.56% lidocaine cream, apply twice daily
• 4% Lidocaine patches can be purchased from ebay, brand name is Salonpas. They last for 8 hours.

Lidocaine Patches

Formulations are Verisatis (5%, not available in NZ), salonpas (4%, available on ebay),

For verisatis up to three plasters can be used at once 12 hours on, 12 hours off. It is a once daily application that provides 24 hour pain relief. No dosage titration is required. It doesn't seem to be easily available.

Toxicity

Main article: Local Anaesthetic Toxicity

The central nervous system is where the premonitory signs of toxicity occur, and it is a graded response. Early symptoms include circumoral numbness, tongue paraesthesia, and dizziness. Patients may complain of sensory disturbance such as tinnitus and blurred vision. There may be excitatory signs, such as restlessness, agitation, nervousness, or paranoia. These may progress to muscle twitching and seizures. With severe toxicity, CNS depression can occur with coma.

Cardiovascular effects with hypotension and bradycardia can occur as a result of a relative overdose with neuraxial blockage or nerve blocks nerve the CNS. Unintentional intravascular injection produces severe cardiotoxic reactions which include hypotension, atrioventicular heart block, idioventricular rhythms, ventricular tachycardia, and ventricular fibrillation. Even premonitory signs can progress to cardiotoxicity and so any reaction should be treated promptly.

Maximum Dose

The maximum safe dose for subcutaneous infiltration typically quoted as:

• Lidocaine WITHOUT adrenaline (also called plain lidocaine) – 4 mg/kg (0.4 mL/kg of lidocaine 1 percent, maximum total dose: 300 mg [30 mL of lidocaine 1 percent])
• Lidocaine WITH adrenaline – 7 mg/kg (0.7 mL/kg of lidocaine 1 percent, maximum total dose: 500 mg [50 mL of lidocaine 1 percent with epinephrine]).

Special considerations:

• In children under 8 years old, 80 percent of the maximum allowable dose should not be exceeded.
• In elderly with severe liver or kidney disease, the total dose should be reduced by around 50%
• The evidence for maximum dosing is actually quite poor, and highly variable dependent on the type of procedure. For example in intercostal nerve blocks the safe dose is 10 times less.

See Also

Buffered Local Anaesthetic

Literature Review

Literature Review

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