Conditions: Neuralgia Postherpetic Neuralgia Reflex Sympathetic Dystrophy Complex Regional Pain Syndrome (CRPS)
Keywords: neuropathic pain postherpetic neuralgia complex regional pain syndrome reflex sympathetic dystrophy
Allocation: RANDOMIZED | Intervention model: CROSSOVER
Enrollment: 35
Healthy volunteers: no

Brief summary:
The purpose of this study is to see if the drug Pennsaid (Diclofenac) can help reduce pain felt by people with chronic nerve pain. The drug will be used 2-4 times each day for 2 weeks.

The U.S. Food and Drug Administration (FDA) has approved Pennsaid to treat osteoarthritis (bone pain), but the FDA has not approved Pennsaid to treat neuropathic (nerve) pain.

The research study will compare Pennsaid to placebo.

Detailed description:
The research study will compare Pennsaid to placebo. The placebo looks like Pennsaid, but it doesn't contain any Pennsaid. The investigators use placebos in research to see if the results are due to the study drug or to other reasons. At some time during the study the investigators will give the patient Pennsaid. At another time, the investigators will give the patient placebo. The investigators are using Quantitative Sensory Testing (QST), which is temperature testing before and after using the study drug to see if Pennsaid is helpful in reducing people's nerve pain.

In this test, a small metal plate, about the size of a matchbox, is put on the area where the patient has pain. The plate is connected to a computer that can warm or cool the plate. The patient will use a computer mouse button to tell us when the plate feels warm. The QST machine is approved by the Food and Drug Administration (FDA). It is often used by nerve doctors to see if a person has neuropathy (pain caused by damage to a nerve).

Arms:
arm 1: Pennsaid (20-40 drops; 2-4 times daily) Upon completion of the first phase, subjects in each arm will be crossed over (i.e., from placebo to Pennsaid and vise versa). Pennsaid or placebo lotion will be packed in a container with identical appearance before being dispensed to study subjects. arm 2: Study subject will topically apply placebo lotion (20-40 drops) 2-4 times daily to the painful area for the next two weeks. The dose titration will be based on the size of painful area (approximately 10 drops for every 4 square inches). Subjects will be asked to fill in a daily pain diary and report any side effects to the research center. A phone number and a beeper number will be provided to subjects.

Interventions: intervention 1: Pennsaid intervention 2: Placebo (2.3% DMSO solution)
Intervention descriptions: intervention 1: None intervention 2: None

Protocol document: