Topical ketamine cream in the treatment of painful diabetic neuropathy: a randomized, placebo-controlled, double-blind initial study.
Painful diabetic neuropathy remains a difficult pathologic condition to manage effectively despite numerous pharmacologic interventions. A randomized, placebo-controlled, double-blind study was undertaken to determine whether topical 5% ketamine cream is effective in reducing the pain of diabetic neuropathy. Seventeen diabetic patients completed the study. The Michigan Neuropathy Screening Instrument was used to determine whether the neuropathy was likely caused by the diabetic condition. Hemoglobin A(1c) levels were measured before treatment. Patients applied 1 mL of either ketamine cream or placebo cream for 1 month. The intensity of seven different pain characteristics was evaluated before and after treatment. A two-way repeated analysis of variance design was used to test for differences between treatments and within patients (time). We found no significant treatment main effect, but pain improved significantly over time in both groups. There was no statistical interaction effect (treatment × time) in any of the pain characteristics, indicating that pain improved in the two treatment groups similarly with time. The 5% topical ketamine cream was no more effective than was placebo in relieving pain caused by diabetic neuropathy.