European journal of pain : EJP
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Randomized Controlled Trial
Differential effects on sensory functions and measures of epidermal nerve fiber density after application of a lidocaine patch (5%) on healthy human skin.
Topical application of lidocaine is an effective approach for treatment of post-herpetic neuralgia and other painful neuropathies. Lidocaine inhibits voltage-gated Na(+) channels and it most likely reduces excitability of cutaneous sensory neurons which can be hyperexcitable or spontaneously active in states of neuropathic pain. However, lidocaine and other local anesthetics also exert a pronounced neurotoxicity and they activate the irritant receptors TRPV1 and TRPA1. ⋯ In conclusion, lidocaine patches seem to have differential effects on sensory modalities in healthy skin. A degeneration of epidermal nerve fibers has previously been demonstrated for patches containing the TRPV1-agonist capsaicin and our findings suggest that this effect might also be relevant for lidocaine patches. These data warrant further studies on molecular mechanisms mediating a relief of neuropathic pain by topical lidocaine.
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Randomized Controlled Trial
Absence of long-term analgesic effect from a short-term S-ketamine infusion on fibromyalgia pain: a randomized, prospective, double blind, active placebo-controlled trial.
To assess the analgesic efficacy of the N-methyl-D-aspartate receptor antagonist S(+)-ketamine on fibromyalgia pain, the authors performed a randomized double blind, active placebo-controlled trial. Twenty-four fibromyalgia patients were randomized to receive a 30-min intravenous infusion with S(+)-ketamine (total dose 0.5mg/kg, n=12) or the active placebo, midazolam (5mg, n=12). Visual Analogue Pain Scores (VAS) and ketamine plasma samples were obtained for 2.5-h following termination of treatment; pain scores derived from the fibromyalgia impact questionnaire (FIQ) were collected weekly during an 8-week follow-up. ⋯ Side effects as measured by the Bowdle questionnaire (which scores for 13 separate psychedelic symptoms) were mild to moderate in both study groups and declined rapidly, indicating adequate blinding of treatments. Efficacy of ketamine was limited and restricted in duration to its pharmacokinetics. The authors argue that a short-term infusion of ketamine is insufficient to induce long-term analgesic effects in fibromyalgia patients.