The treatment of pain has improved immeasurably over the last few decades but there are still circumstances where our attempts to gain analgesia are thwarted by either therapeutic failure or production of intolerable side effects.
"Conventional" pharmacological treatment revolves around the use of acetaminophen, opioids and non-steroidal anti-inflammatories, with the use of antidepressants, anti-epileptics, membrane stabilizers and N-methyl-D-aspartate (NMDA) antagonists in particular circumstances, and requires the patients to either ingest or apply transdermally medication on a regular day-in, day-out basis. Where longer dosing intervals are appropriate, this is because extended release preparations are used. The aim is to achieve a steady state plasma concentration of the drug so that pain relief may be obtained. Unfortunately this may also expose the patient to day-in, day-out side effects with these side effects ranging from the trivial to the severe end of the spectrum and may be immediately obvious or more insidious.
The concept with the use of intravenous (IV) lidocaine is radically different. Here the drug is administered over a relatively short period of time and yet the potential relief lasts significantly beyond both the period of administration and the plasma half-life of this local anesthetic. Indeed, as will be described later, an infusion over a few hours can produce relief that extends to weeks and even months. Consequently, side effects, if any are apparent, are short-lived and last for a much shorter time than the pain relief. Indeed, IV lidocaine can be the sole analgesic, and between infusions the patient is essentially "drug free." A secondary potential benefit of IV lidocaine is that it may produce pain relief when all other modalities of pain treatment have failed.
It could therefore be argued that this concept has much appeal. However, it must be remembered that the use of IV lidocaine does not produce pain relief in all patients; but then again, neither does any other pain treatment.
In this chapter the following considerations will be examined:
• Mode of action of IV lidocaine
• The animal experimental evidence of an antinociceptive effect of systemic lidocaine
• The human experimental evidence of a pain relieving effect
• The human clinical evidence
• The safety (particularly cardiovascular safety) of IV lidocaine
• Suggested clinical use
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