Articles: pain.
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Capsaicin injected intradermally into the human forearm lowered the pain threshold for heat at the injection site. Both the magnitude and duration of hyperalgesia were dose dependent over the range of 0.1-100 micrograms, given in a constant volume of 10 microliter. Thus, capsaicin may be a useful tool in studies of the neural mechanisms of hyperalgesia.
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Administration of narcotic analgesics through the epidural route has proven useful for treating pain of acute and chronic nature. This route of narcotic administration is frequently chosen for cancer patients with intractable pain that may be refractory to treatment by conventional oral or parenteral therapy. ⋯ The patient has achieved stable pain relief for greater than 8 months without hospital admission for pain control, or management of complications due to the drug delivery system. The Travenol Infusor may prove to be an alternative drug delivery system for patients requiring continuous epidural narcotic infusion.
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Counterirritation, the phenomenon of one painful stimulus reducing pain caused by a second noxious stimulus, has been recognized clinically for decades. Recently a physiological mechanism to explain counterirritation was described and termed diffuse noxious inhibitory controls (DNICs). Nevertheless, few psychophysical studies have examined systematically the effects of a noxious conditioning stimulus on pain perception. ⋯ Similarly, the pain threshold was significantly increased from 45.7 degrees C to 47.3 degrees C while the hand was in cold water and this threshold remained elevated after the cold water was terminated. Since DNICs have been found to completely and selectively inhibit the activity of only one type of pain transmission neuron (wide dynamic range), our data suggest that these neurons are involved in the perception of pain intensity. However, the persistence of residual pain perception in the presence of noxious conditioning stimuli indicates the importance of other nociceptive pathways.