Articles: hyperalgesia.
-
Randomized Controlled Trial
Classical conditioning and expectancy in placebo hypoalgesia: a randomized controlled study in patients with atopic dermatitis and persons with healthy skin.
The effectiveness of placebos is unchallenged. However, it is still not clear on which mechanisms the placebo effect is based. Besides expectancy theories, classical conditioning is discussed as a major explanatory model. ⋯ However, conditioning processes seem to be necessary for a longer lasting effect. The extent of this effect seemed to be greater in atopics than in healthy controls. Expectancy, achieved through verbal instruction, might also be seen as a conditioned stimulus that reactivates earlier stimulus associations.
-
Randomized Controlled Trial
Effects of oral pregabalin and aprepitant on pain and central sensitization in the electrical hyperalgesia model in human volunteers.
Central sensitization is an important mechanism of neuropathic pain; its human models could be useful for early detection of efficacy of novel treatments. The electrical hyperalgesia model invokes central sensitization by repetitive stimulation of the skin. To assess its predictive value, we have investigated pregabalin, a standard neuropathic pain treatment, and aprepitant, an NK(1) antagonist, as an example of a drug class active in animal models but not in neuropathic pain patients. Furthermore, we explored if combinations of either of these drugs with the COX-2 inhibitor parecoxib could improve its efficacy. ⋯ The model can serve to predict analgesic efficacy in early human development and investigate the mechanism of action. The model could also be used to explore efficacy of analgesic combinations to provide a rationale for patient studies.
-
Aliment. Pharmacol. Ther. · Feb 2007
Randomized Controlled TrialNeurokinin-1 receptor antagonism in a human model of visceral hypersensitivity.
Substance P acting via the neurokinin-1 receptor is involved in the development of hyperalgesia, although studies using neurokinin-1 receptor antagonists (NK-1RA) in human somatic pain have been disappointing. ⋯ The lack of effect of NK-1RA on oesophageal pain threshold in our model does not support a role for Substance P in the development of acid-induced oesophageal allodynia.
-
Randomized Controlled Trial Comparative Study
Placebo-controlled comparison of a morphine/dextromethorphan combination with morphine on experimental pain and hyperalgesia in healthy volunteers.
In this double-blind, placebo-controlled, crossover study we compared the analgesic effect of a single oral dose of 30-mg dextromethorphan and 30-mg morphine combination (MS/DM) to 30 mg morphine (MS) alone and either placebo or 30 mg dextromethorphan (DM) on cutaneous sensitization induced by heat/capsaicin (topical) sensitization on the forearm and the brief thermal sensitization model on the thigh in 22 healthy volunteers. Outcome measures were areas of secondary hyperalgesia to brush and von Frey hair stimulation in both sensitization models and the painfulness of acute thermal noxious stimulation on the upper arm. Compared with placebo, both MS/DM and morphine had some effect on the secondary hyperalgesia and reduced the painfulness of a noxious thermal stimulus. The analgesic effect of MS/DM was not superior to that of morphine on any outcome measure. These results differ from preclinical studies with animal experimental pain models in which DM markedly potentiated the analgesic effects of opioids, but they are in accordance with recent clinical trials for chronic pain. ⋯ Adding dextromethorphan to morphine (1:1 ratio) did not enhance analgesia on measures of experimental cutaneous sensitization and acute noxious thermal stimulation in healthy volunteers. The results differ from preclinical studies but agree with clinical trials. Human experimental models of pain and neuronal sensitization, which are responsive to oral opioids, allow efficient study of opioid combination analgesics and simplify the process for determining the optimal dose and/or dose ratio.
-
Randomized Controlled Trial
Multiple dose gabapentin attenuates cutaneous pain and central sensitisation but not muscle pain in healthy volunteers.
Various muscle pains constitute a large clinical problem, both for patients and clinicians. Gabapentin is an established therapy in neuropathic pain and reduces cutaneous pain in healthy volunteers. Gabapentin in combination with other analgesics reduces post-operative pain. ⋯ Mechanical pain thresholds were unaffected. Pain induced by intramuscular infusion of hypertonic saline was not affected by gabapentin. In conclusion, single or repeated dosing of gabapentin reduced cutaneous but not muscle pain in healthy volunteers.