Obscure ‘morphine-like’ drug less likely to cause constipation than morphine, more potent, longer lasting

The drug also worked better with neuropathic and inflammatory pain in animal trials, and tolerance developed more slowly.

A little-known morphinelike drug is potentially more potent, longer lasting and less likely to cause constipation than standard morphine, a study led by a Loyola University Health System anesthesiologist has found.

The drug, morphine-6-0-sulfate, has a similar chemical structure to standard morphine. Loyola University pain expert
Joseph Holtman Jr. MD, PhD,  and colleagues* reported in the Dec 2010 issue of the European Journal of Pharmacology(1) that a study they performed in rats "demonstrated potential clinical advantages of morphine-6-0-sulfate compared to morphine."

Opioids, such as morphine, oxycodone and hydrocodone, are standard drugs for treating moderate to severe pain, including cancer pain.

• But these drugs can have significant side effects, including constipation, nausea, vomiting, drowsiness, cognitive dysfunction and slowed breathing and heart rates.

• And while opioids work well for conditions such as back pain and post-operative pain, the drugs are less effective against neuropathic pain, such as tingling, burning or shooting pain.

Constipation is a common side effect of morphine and can be so uncomfortable that some patients limit their use of the drug. Doctors typically do not discharge surgery patients until they have had a bowel movement and this can extend hospital stays.

Holtman and colleagues tested standard morphine and morphine-6-0-sulfate on rats. The animals received the drugs three ways – by mouth, by IV and by injection into the space surrounding the spinal cord.

The rats underwent several well-established tests to determine their sensitivity to pain. In one such test, researchers focused a very warm light beam on the tail and measured how long it took for the rat to flick the tail.

In this tail-flick test, morphine-6-0-sulfate was:

• 10 times more potent than standard morphine when administered in the space surrounding the spinal cord,

• 5 times more potent when administered by IV and

• 2 times more potent when given by mouth.

Morphine-6-0-sulfate maintained its maximum effect for three hours, compared with 1½ hours for standard morphine.

And it took rats 25 days to build tolerance to morphine-6-0-sulfate, compared with 10 days with standard morphine.

Morphine-6-0-sulfate also was more potent than standard morphine for neuropathic and inflammatory pain.

Researchers found that morphine-6-0-sulfate could cause constipation, but only at doses 10 to 20 times higher than the effective doses.

The findings suggest that morphine-6-0-sulfate "may be an interesting potential drug for further study," Dr. Holtman and colleagues wrote.

____

* The study was conducted at the University of Kentucky, where Dr. Holtman's co-authors all work and where he worked until March 2010. The study was funded by Insys Therapeutic, Inc., which is has a license to develop the drug for possible use in humans.

1. “Antinociceptive effects and toxicity of morphine-6-0-sulfate socidum salt in rat models of pain,” European Journal of Pharmacology, Dec 1, 2010, by Holtman JR Jr., et al.

Source: Loyola University Health System news release, Jan 4, 2011  

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One thought on “Obscure ‘morphine-like’ drug less likely to cause constipation than morphine, more potent, longer lasting”

  1. Achyten says:

    I’m very interested in this drug, being that its less likely to cause constipation..
    I suffer from back pain due to bulging discs, DDD,osteo arthritis, etc. and fibromyalgia. I have to take opiods to help me through the days,, and even though I”m not on high doses, I suffer from constipation all the time.
    So, this new morphine-like drug sounds like something I”d like to try,,but it sounds like this is only in the beginning stages of being available to humans,,, and only rats have been tested with..
    I hope this drug will be available for us in the near future…
    achyten

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