The Clinical journal of pain
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Clinical Trial
Topical lidocaine patch relieves a variety of neuropathic pain conditions: an open-label study.
Our goal was to perform a pilot study to assess the effectiveness and tolerability of a topical lidocaine patch (Lidoderm) for the treatment of peripheral neuropathic pain conditions other than postherpetic neuralgia. ⋯ The Lidoderm patch provided clinically meaningful pain relief in most of these refractory neuropathic pain patients without side effects. Controlled trials need to be performed to confirm these preliminary findings.
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Case Reports Comparative Study
Severe lightning pain after subarachnoid block in a patient with neuropathic pain of central origin: which drug is best to treat the pain?
There have been many reports that spinal anesthesia induces severe lightning pain in the lower limbs of patients with phantom limb pain, tabes dorsalis, or causalgia. We report on a patient with neuropathic pain of central origin who showed newly developed severe lightning pain after therapeutic subarachnoid block (SAB). We performed SAB 16 times in this patient, and he complained of severe pain each time. We investigated which drug was best for treating such induced pain by administering various drugs to the patient. ⋯ Intravenous thiopental, fentanyl, butorphanol, ketamine, midazolam, droperidol, and sevoflurane-oxygen anesthesia were quite effective. Intramuscular butorphanol was not effective. Intravenous physiologic saline and atropine sulfate as a placebo, intrathecal morphine hydrochloride, intravenous mexiletine, and lidocaine were ineffective. Intravenous thiopental (approximately 1 mg/kg) was thought to obtain the best pain relief because it stopped the pain quickly, the dose needed was subanesthetic, and there was no adverse effect.
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In almost every neuropathic pain state caused by peripheral nerve damage, whether due to trauma or disease, both structural damage and an inflammatory response exist. ⋯ These data suggest the possibility of an important interaction between the immune system and the nervous system in neuropathic pain and suggest that drugs modulating the immune system may be useful therapies in at least some neuropathic pain states.
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Several independent pathophysiological mechanisms in both the peripheral and central nervous system are responsible for sensory symptoms as well as spontaneous and evoked pains in peripheral neuropathies: (1) Pathologic active or sensitized nociceptors can induce secondary changes in central processing, leading to spinal cord hyperexcitability that causes input from mechanoreceptive Abeta-fibers (light touching) to be perceived as pain. These patients characteristically have spontaneous pain, heat hyperalgesia, static mechanical allodynia, and and severe dynamic mechanical allodynia. (2) Nociceptor function may be selectively impaired within the allodynic skin. Pain and temperature sensation are profoundly impaired but light moving mechanical stimuli can often produce severe pain (dynamic mechanical allodynia). ⋯ A thorough analysis of sensory symptoms may, reveal the underlying mechanisms that are mainly active in a particular patient. The treatment of neuropathic pain is currently unsatisfactory. In the future, drugs will be developed that address specifically the relevant combination of mechanisms.