Anesthesia and analgesia
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Anesthesia and analgesia · Jul 2009
Comparative StudyMexiletine and lidocaine suppress the excitability of dorsal horn neurons.
Spinal sensitization and facilitatory processes in dorsal horn neurons after nerve injury alter spinal outflow leading to enhanced pain perception and chronic pain syndromes. Clinically used Na+ channel blockers at doses which do not block conduction can relieve such chronic pain. Although much attention has been paid to their effect upon afferents, less work has been done with their effect on the excitability of central sensory neurons. Thus, we investigated the effects of the Na+ channel blockers mexiletine and lidocaine on sensory spinal dorsal horn neurons. ⋯ In clinically relevant concentrations, lidocaine and mexiletine reduced the excitability of sensory dorsal horn neurons via a blockade of Na+ and K+ channels. Our work confirms that, in addition to the peripheral effects of lidocaine and mexiletine, modulation of voltage-gated ion channels in the central nervous system contributes to the antinociceptive effects of these drugs used in pain therapy.
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Anesthesia and analgesia · Jul 2009
Comparative StudyInstilled or injected purified natural capsaicin has no adverse effects on rat hindlimb sensory-motor behavior or osteotomy repair.
A novel formulation of > or = 98% pure capsaicin (4975) is currently undergoing clinical investigation using novel routes of delivery to provide selective analgesia lasting weeks to months with a single dose. We conducted this study to assess the safety and effects of instilled and injected 4975 in rat models of wound healing osteotomy repair and sensory-motor nerve function. ⋯ A single, clinically relevant application of instilled or injected 4975 has no observable adverse effect on wound and bone healing after osteotomy or on the structural integrity of exposed muscle and nerve.