Pain
-
Randomized Controlled Trial
GABAergic modulation in central sensitization in humans: a randomized placebo-controlled pharmacokinetic-pharmacodynamic study comparing clobazam with clonazepam in healthy volunteers.
Positive allosteric modulators of GABAA receptors (GAMs) acting at specific subtypes of GABAA receptors effectively restore compromised spinal pain control in rodents. Studies addressing a similar antihyperalgesic effect in humans are sparse and are hampered by sedative effects of nonselective GAMs available for use in humans. We present results from a randomized controlled double-blind crossover study in 25 healthy volunteers, which addressed potential antihyperalgesic actions of clobazam (CBZ) and clonazepam (CLN) at mildly sedating equianticonvulsive doses. ⋯ Active compounds induced stronger sedation than placebo, but these differences disappeared 8 hours after drug application. We demonstrate here that GAMs effectively reduce central sensitization in healthy volunteers. These results provide proof-of-principle evidence supporting efficacy of GAMs as antihyperalgesic agents in humans and should stimulate further research on compounds with improved subtype specificity.
-
Randomized Controlled Trial
A new objective method for acquisition and quantification of reflex receptive fields.
The nociceptive withdrawal reflex (NWR) is a polysynaptic spinal reflex correlated with pain perception. Assessment of this objective physiological measure constitutes the core of existing methods for quantification of reflex receptive fields (RRFs), which however still suffer from a certain degree of subjective involvement. This article proposes a strictly objective methodology for RRF quantification based on automated identification of NWR thresholds (NWR-Ts). ⋯ The NWR-T-based quantifications required a smaller sample size than any of the existing RRF measures to detect a clinically relevant effect in a crossover study design involving more than 1 session. Of all measures, quantification from mapping of inversed NWR-Ts demonstrated superior reliability both within (CR, 0.25) and between sessions (CR, 0.28). The study presents a more reliable and robust quantification of the RRF to be used as biomarker of pain hypersensitivity in clinical and experimental research.
-
Randomized Controlled Trial
Spinal cord stimulation attenuates temporal summation in patients with neuropathic pain.
Evidence has shown that electrical stimulation at the dorsal columns attenuated the "wind-up" phenomenon in dorsal horn neurons in nerve-injured rats. This study was aimed to test the effect of spinal cord stimulation (SCS) on temporal summation (TS), the clinical correlate of the wind-up phenomenon in patients with radicular leg pain. Eighteen patients with SCS implants were tested both 30 minutes after SCS activation ("ON") and 2 hours after turning it off ("OFF"), in a random order. ⋯ In the nonpainful leg, SCS activation failed to produce an effect on TS (24 ± 20 vs 21 ± 24 in SCS "OFF" and "ON", respectively; P = 0.277). In contrast, a significant decrease in the magnitude of TS in the affected leg was observed in response to SCS activation (from 32 ± 33 to 19 ± 24; P = 0.017). These results suggest that attenuation of TS, which likely represents suppression of hyperexcitability in spinal cord neurons, is a possible mechanism underlying SCS analgesia in patients with neuropathic pain.