In a recent study it has been found that morphine-like drug is more potent and long lasting and less likely to cause constipation than standard morphine. The drug, morphine-6-0-sulfate, has a similar chemical structure to standard morphine.
Loyola University Health System anaesthesiologist Dr. Joseph Holtman Jr. and colleagues reported 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 can have significant side effects, including constipation, nausea, vomiting, drowsiness, cognitive dysfunction and slowed breathing and heart rates.
The researchers tested standard morphine and morphine-6-0-sulfate on rats which received the drugs three ways - by mouth, by IV and by injection into the space surrounding the spinal cord.
The animals then underwent several tests to determine their sensitivity to pain. In one such test, the 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, five times more potent when administered by IV and two times more potent when given by mouth.
Morphine-6-0-sulfate maintained its maximum effect for three hours, compared with 1.5 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 suggested that morphine-6-0-sulfate 'may be an interesting potential drug for further study', said Holtman.
The study has been published in the December 2010 issue of the European Journal of Pharmacology.