(HealthDay News) — Using subcutaneously administered ketamine in a dose-escalating regimen as an adjunct to opioids and standard co-analgesics does not have any clinical benefit in relieving cancer pain, but it is associated with increased toxicity, according to research published online Sept. 10 in the Journal of Clinical Oncology.

Janet Hardy, M.D., of the Mater Adult Hospital in South Brisbane, Australia, and colleagues conducted a multisite, dose-escalation, randomized, double-blind, placebo-controlled trial involving 185 patients with advanced cancer to evaluate the use of ketamine or placebo delivered subcutaneously over three to five days. The authors sought to determine whether the addition of ketamine to opioids improves the management of chronic uncontrolled cancer pain.

The researchers observed no significant difference between patients receiving ketamine or placebo, and it did not matter whether pain was nociceptive or neuropathic. However, there were nearly double the adverse events with ketamine compared with placebo, including a greater risk of severe adverse events (odds ratio, 1.09; 95 percent confidence interval, 1.00 to 1.18). For one positive outcome to be achieved with ketamine use, the number needed to treat was 25, compared with a number needed to harm of only six.

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“This large randomized controlled trial demonstrated a strong placebo effect and failed to show any additional clinical benefit for ketamine when delivered subcutaneously in a dose-escalating regimen over five days, while significantly increasing toxicity,” the authors write.

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