Psychophysical Correlates of Pain Reduction by Topical Analgesic Compounds

Study Summary

Background: \- Researchers are studying a topical (skin) cream that reduces pain. This is called an analgesic cream. They want to try a new test to better measure how well it works. Heat will be applied to the participants arms and they will judge the intensity of the temperatures. Researchers will compare the pain reduction from this cream to other pain relief treatments. Objective: \- To better measure the effects of a pain-relieving (analgesic) cream. Eligibility: \- Healthy volunteers ages 18 50. Design: * There will be 2 study sessions. * Session 1 will be about 1.5 hours. * Participants will be screened with physical exam and urine drug test. They will answer medical and psychological questions. * Participants will have sensory testing. * A moisturizer will be put on their arms. A heating device will be placed on their arms. It gives heat pulses of about 2 seconds each. Some are warm and some are very hot. Participants will say how strong each pulse is. They can move away if it gets painful. * Then the pain-relieving cream will be put on one arm. The moisturizer will be put on the other. Participants will get more pulses and rate them. They will also get pairs of pulses and compare them. * Some participants will return for session 2 for 1 hour. They will receive similar sensory testing as in session 1.