BREAKTHROUGH IN PAINKILLING

NEWS - Researchers at Queen's University have made a discovery that could
lead to safer and more effective use of morphine and other painkillers.

Their groundbreaking research, which could change the way people suffering
from chronic diseases deal with severe pain, will appear next month in the
Journal of Pharmacology and Experimental Therapeutics.

Dr. Khem Jhamandas, who headed the research at Queen's, said his team found
that small doses of drugs known as opioid antagonists - normally used to
block the toxic effects of opioids such as morphine - can actually enhance
painkilling action.

Their surprising finding also showed that the combination of small amounts
of opioids and opioid antagonists stopped the development of a tolerance to
morphine, and in cases where tolerance had already developed, it was
actually reversed.

The experiments conducted at Queen's reveal that in cases where tolerance
had developed, the effectiveness of morphine was restored to between 80 and
90 per cent of the original dose.

"When we received the results from the first experiment, I couldn't believe
it," said Jhamandas, who works in Queen's Department of Pharmacology and
Toxicology.

"Everything we knew up to that point indicated it shouldn't work. One would
not think to combine a morphine antagonist with morphine in small doses."

Both types of drugs act on opioid receptors which are located on nerve
cells that transmit pain signals. When activated by morphine, these
receptors will powerfully suppress pain.

Combining an opioid "agonist" such as morphine with its antagonist - in
this case, the drug naltrexone - is a radical approach that was sparked by
scientific literature that suggests morphine and other opioids have both
stimulatory and depressant effects, said Jhamandas.

Funded by the Canadian Institutes of Health Research, the study could lead
to the development of more effective painkilling drugs that require lower
dosages, have fewer side-effects and remain effective with repeated use.
The study's results are particularly exciting for patients with chronic
illnesses that require long-term use of these drugs to control their pain.
The discovery could also lead to the development of drugs to treat
neuropathic pain, which results from nerve injury and doesn't respond well
to opioids.

"This is exciting because there are so many potent chemicals in the brain
that can influence pain, and we're just beginning to comprehend their
functions and their promise for yielding treatments providing optimal pain
relief," said Jhamandas.

"In understanding how pain transmissions occur, we're learning the biology
of pain with the objective of making drugs that will work better."

Jhamandas said he isn't sure when clinical trials will begin on the
discovery, but he's sure there will be interest in the finding. "Clinical
trials will have to be done to support our claim," he added.

The Queen's study was conducted by a multidisciplinary research team
composed of Jhamandas and graduate students Kelly Powell and Noura
Abul-Husn from the pharmacology and toxicology department, as well as Asha
Jhamandas, Mary Olmstead and Richard Benninger from the psychology department.