Study Suggests Drug Similar to Marijuana Ingredient Helps Head Injuries
http://more.abcnews.go.com/sections/living/dailynews/cannabinoid011005.html
Oct. 5, 2001
Could a drug similar to the active
ingredient in marijuana protect your brain?
Mice that sustained brain injuries
were discovered to have elevated levels of a compound known as 2-Arachodonoyl
glycerol, or 2-AG. Theorizing that this cannabinoid was produced to prevent
damage, the researchers administered more of the compound to injured mice
and found it protected the brain.
Treatment
Currently, there is no effective
drug for the treatment of traumatic brain injury. In the U.S., there are
nearly 52,000 deaths and roughly 80,000 cases of severe disability related
to traumatic brain injury every year.
There are more than 5.3 million people
in the U.S. living with disabilities related to traumatic brain injury
— numbers far greater than those for multiple sclerosis, Parkinson's disease
and Alzheimer's disease.
"Brain injury is not a one-shot deal.
The primary injury occurs from the initial hit. Neurochemical injuries
can cause secondary damage," said Dr. Ken Strauss of Temple University.
The secondary effects of brain injuries,
such as swelling and the release of toxic chemicals, can be more damaging
than the initial blow, said Dr. Esther Shohami, lead author of the study.
The cannabinoid, 2-AG, is believed
to work in three ways. First, it reduces the levels of glutamate, a toxic
molecule, released after injury. Second, it decreases the amount of free
radicals and TNF (a chemical that induces inflammation) after injury. Third,
it increases the blood supply to the brain. All three mechanisms are essential
for limiting the damage done after the primary injury.
"The dose has to be very carefully
controlled," Dr. Shohami said — noting that requirement is one of a number
of reasons why marijuana, which can vary in potency, would likely be an
unreliable treatment for head injuries.
She added that 2-AG must be administered
within a four- to six-hour window after the injury to be effective.
Use in Humans
Although 2-AG has only been tested
on animals, Dr. Shohami said she didn't "see any problems with using a
drug from this family to treat patients." Other cannabinoids have been
approved for use in humans, such as synthetic forms of THC used to stimulate
appetite.
In fact, one pharmaceutical company
is trying to develop a similar drug for humans. With the help of researchers
at the Hebrew University, Pharmos is set to begin the final stage of clinical
trials of Dexanabinol — a drug that is essentially the mirror image of
THC, the active ingredient in marijuana. Because it is not exactly like
THC, it does not bind to the same part of the brain, and therefore does
not have the unwanted side effects.
However, the drug appears to exert
effects similar to other cannabinoids on the brain after injury — that
is, a decrease in toxic chemicals and swelling. The first two phases of
clinical trials were completed in Israel to test for safety. The third
and final phase of the trials is set to begin in Europe in January, followed
closely by trials in the U.S.
"Helmets are for preventing primary
injury, and hopefully this work can protect people from the secondary effects,"
Dr. Strauss said.
By Jeffrey Carpenter
Research at the Hebrew University
in Israel, reported in the journal Nature, shows that a cannabinoid, similar
to the active ingredient found in marijuana and produced in the brains
of many animals, protects mice from brain injury.