Pain
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Pharmacological actions on the nociceptive flexion flexes of the hindlimb were investigated in 14 normal subjects. These reflexes were used as an index of pain and were recorded in the biceps femoris muscle, elicited by electrical stimulation of the ipsilateral sural nerve (RIII,su) and of the skin in the distal receptive field of this nerve (RIII,Cu). The ratio of the threshold of RIII,Cu/RIII,Su was calculated since it gives an indication on the mechanism and the efficacy of the drug. ⋯ In contrast, pethidine provoked a decrease in the RIII,Su threshold and an increase in RIII,Cu threshold, parallel with an increase in pain threshold sensation. The ratio was found to be 190% at the maximal effect. Practical implications of these results, concerning a method for testing the efficacy and mechamisms of an analgesic, are then discussed.
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Clinical Trial Controlled Clinical Trial
On the sensitivity of the tourniquet pain test.
Twenty-four chronic pain patients were given, on each of 4 successive days, oral doses of 60 mg morphine, 60 mg codeine, 600 mg aspirin and placebo, using a double-blind counterbalanced design. Two hours after ingestion, subjective pain estimates and tourniquet pain scores were obtained. ⋯ However, differences in pain estimates were also too small to discriminate among the drugs, and the lack of sensitivity may be a function of pain chronicity. The tourniquet techniques will continue to be useful until there is a purely objective measure of the severity of clinical pain.