Pain relievers found in many medicine cabinets may help prevent some of the learning and memory problems often experienced by people who regularly use medical marijuana, a new study suggests.

In a series of experiments done on mice, researchers found they could prevent or lessen marijuana's cognitive side effects by giving the drug's active ingredient, a chemical called delta-9-tetrahydrocannabinol (THC), in combination with either Celebrex, a prescription pain reliever, or ibuprofen, an over-the-counter nonsteroidal anti-inflammatory drug (NSAID).

"Our findings suggest that the unwanted side effects of cannabis could be eliminated or reduced, while its beneficial effects can be retained," said study researcher Chu Chen, a professor of neuroscience at Louisiana State University Health Sciences Center in New Orleans. [Trippy Tales: The History of 8 Hallucinogens]

Chen said his team is planning to continue their research in humans in the near future, to see if the findings hold true.

The findings were published online today (Nov. 21) in the journal Cell.

Preventing side effects

Marijuana has been used as a medical treatment for a few thousand years, Chen said. The drug has been used to ease symptoms for everything from chronic pain and multiple sclerosis to cancer and seizure disorders.

However, the unwanted effects of cannabis greatly limit its medical use, Chen told LiveScience. So his research team set out to understand the molecular mechanisms underlying these adverse effects.

The researchers found that mice treated with THC had an increase in levels of a chemical called cyclooxygenase-2 (COX-2) in the hippocampus, a partof the brain involved in memory and learning.

"We uncovered the riddle of the marijuana-caused adverse effects, and its signaling pathway," Chen said.

This led the researchers to test the effects of giving the mice drugs that lower COX-2 levels, including Celebrex and ibuprofen.

The findings suggest that giving people a COX-2 inhibitor drug along with medical marijuana may help to reduce the memory and learning problems linked with its long-term treatment, the researchers said.

But further testing is needed in human clinical trials. At this point, it's still too early to determine the dose or frequency of Celebrex or ibuprofen that could be given to prevent marijuana-induced side effects, or to say when the pain relievers should be taken, Chen said.

Broader medical use

Marinol is the brand name of the prescription marijuana medication currently approved in the United Statesto treat the nausea and vomiting caused by chemotherapy.

But some people are put off by the memory loss, confusion and sleepiness that can come with regularly taking Marinol, which greatly limits its use.

Based on the new findings, researchers may be able to broaden the medical use of marijuana by reducing its undesirable effects while retaining its beneficial properties, Chen said.

Chen said he suspects his findings can be applied to both Marinol and the smokable form of medical marijuana, which is now legal in some states. But he cautioned that smoking pot may also affect the lungs, a reason why some pharmaceutical manufacturers have developed a spray form of cannabis that is spritzed into the mouth.

When asked whether these findings might apply to people who smoke pot recreationally, Chen said it depends on how much marijuana they use.

"The memory impairments occur only in people who use marijuana heavily," he said.

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