Lidocaine

Introduction

  • Lidocaine is an amide local anaesthetic that is a non-selective sodium channel blocker
  • acts by suppressing ectopic neural discharges originating from injured afferent fibres by blocking sodium channels – damaged neurons more sensitive to Lidocaine.
  • also has effects on brain sodium channels
  • does not have any effect on the normal function of other sensory/motor neurones.
  • has effect on lowering susceptibility to all types of pain
  • activates endogenous opioid system.

Pharmacology
a) Indications

  • Neuropathic pain

a) Difficult pain not responding to other analgesics
b) In terminal phase

  • Any difficult pains not responding to optimal treatment.

b) Contraindications

  • hepatic disease
  • cardiac arrhythmias, complete block
  • Epilepsy
  • cautions: epilepsy, shock brady cardia

c) Drug Interactions

  • other anaesthetics
  • antiarrhythmic drugs
  • increased risk with drugs that prolong QT interval
  • Beta Blockers
  • Cimtidine

d) Available Preparations
1% Lidocaine hydrochloride 10mg/ml – 2,5,10,20ml
2% Lidocaine Hydrochloride 20mg/ml – 2,5ml

e) Side Effects

  • light-headedness, dizziness, somnolence increases risk with perianal numbness increasing dose
  • Headache
  • respiratory depression
  • Hallucinations
  • seizure

Guidelines
a) Administration/Dose
i) occasionally given IV as test dose equates to +100mg per day 1-5mg/kg (usual starting dose)
ii) pulse therapy (CSCI)
given via CSCI over 6-24 hours
increase by 100mg/day until response obtained
once response obtained continue at same dose for 5 days then stop infusion
can repeat infusion when pain returns
maximum dose 600mg/24hours
b) Prevention of Side Effects

  • consider reduction of opioids when commencing Lidocaine
  • no oral equivalent to Lidocaine but good response may suggest that oral
  • Mexilitine could be effective in maintaining analgesic control

Monitoring During Treatment
Baseline and then half hourly for first 2 hours, then 4 hourly thereafter:

  • heart rate/pulse
  • respiratory rate
  • BP
  • ECG – repeat ECG with each increase in dose or significant alteration in heart rate or rhythm
  • O2 sats – if less than 90% consider treatment whilst on O2 to maintain saturation at less than 95%
  • If any significant changes in observations notify doctors ASAP

References/Bibliography
Attal 2000
Attal 2004
Jauren Mae 2000
Cahara 2004
Kvanstrom & Karlsten 2003
Kvanstrom & Karlsen 2004
Ferrine (JPM) 2000
Tremont-Luklats et al 2005
BNF

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