Psychophysical Correlates of Pain Reduction by Topical Analgesic Compounds

This study uses a new testing design to evaluate pain reduction from a pain-relieving cream. Sequences of heat stimuli will be applied to the participants arms and participants will be asked to judge the intensity of the temperatures they perceive. There are two study sessions. Session 1 involves eligibility screening and baseline sensory testing with and without the analgesic (pain-relieving) cream. Session 2 involves more sensory testing with the analgesic cream. The study population is 40 healthy volunteers aged 18 to 50.

• INCLUSION CRITERIA:

You may be eligible to participate in this research study if you are:

• Between 18 and 50 years old.
• Fluent in English.
• Able to understand the procedures described in this document and give your written consent.

Exclusion criteria

You may not be eligible to participate in this research study if you:

• Cannot complete the required procedures and tests in the study
• Used recreational drugs within the past six months
• Are in the third trimester of pregnancy
• Have a major medical condition or major medical history event that could affect touch and pain
• Have a medical condition that might affect touch and pain (e.g. Raynaud s Disease, peripheral neuropathy, or circulatory disorder)
• Have chronic pain or a history or chronic pain
• Have allergies to topical treatments
• Have a dermatological condition such as scars or burns, or have had a tattoo on your forearms within the previous four weeks that might influence touch or pain
• Had a recent or permanent injury of upper limbs or amputation or use a prosthetic limb
• Have participated in related NIH protocols (we will determine this)
• Used non-steroidal anti-inflammatory drugs (NSAIDS, e.g. aspirin, ibuprofen), acetaminophen, or sumatriptan within 3 days of testing (brand names include Advil, Tylenol, and Imitrex)
• Used narcotics (e.g. opioids, oxycodone) or pseudo narcotics (e.g. tramadol, tapentadol) within one week of testing (brand names include Percocet and Ultram)
• Use centrally acting medications like anticonvulsants (e.g. gabapentin, pregabalin), antidepressants (e.g. fluoxetine, duloxetine), antipsychotics (e.g. chlorpromazine, prochlorperazine), or anxiolytics (e.g. clonazepam, alprazolam) (Brand names include Neurontin, Lyrica, Prozac, Cymbalta, and Xanax)
• Use tobacco daily or used tobacco within 24 hours of testing
• Used topical pain-relieving creams in the testing area (e.g. methylsalicylate, capsaicin) within 24 hours of testing (Brand names include IcyHot and BenGay)
• Cannot schedule two sessions within two weeks
• Have consumed caffeine before 2 hours of testing