Painkiller blocks unwanted effects of morphine

By David Douglas

NEW YORK (Reuters Health) - In a mouse model of breast cancer, the COX-2 inhibitor celecoxib (Celebrex) prevents chronic morphine-induced effects on tumor growth without compromising pain relief, scientists report.

"Our study," chief scientist Dr. Kalpna Gupta, told Reuters Health, "provides a proof of principle" that morphine increases COX-2, tumor development, tumor progression and tumor spread, and reduces survival in mice.

"Co-administration of celecoxib prevents these effects of morphine," Gupta said.

In the British Journal of Cancer, Gupta, of the University of Minnesota, Minneapolis and colleagues report that 2 weeks of morphine treatment in mice with breast cancer led to a more than fourfold increase in levels of COX-2 and prostaglandin E2 (PGE2) -- a chemical known to promote inflammation. Morphine administration also increased tumor weight by about 35 percent.

The team found that the addition of celecoxib to the morphine treatment prevented the stimulation of COX-2 and PGE2 and associated tumor-related effects.

In addition, 70 percent of mice treated with morphine only died by day 14 compared to 20 percent of mice given the combination.

"Importantly," continued Gupta, "the combination of morphine and celecoxib provides better analgesia than either of them alone."

"Therefore," he concluded, "clinical trials are warranted to examine that this strategy can be applied to treat pain in patients with cancer."

SOURCE: British Journal of Cancer, November 2007.