Among other things, marijuana is known to relieve pain. Scientists believe the cannibinoids deserve the credit, though they're not exactly sure how they work their magic. Unfortunately, the cannibinoids also get into the brain, where they can cause a variety of problems.
So researchers at UC Irvine and their colleagues set out to design a molecule that relieves pain like cannibinoids, but doesn't cause any mischief in the brain.
They started with a compound called URB597, which is a known analgesic. Then they added chemical groups to it, making it bigger. One of the combinations – which they dubbed URB937 – acted the same way but didn't stick in the central nervous system or brain.
Further tests revealed that the new compound probably does cross the blood-brain barrier, but gets “extruded” from the central nervous system. However, it did travel rapidly throughout the body, hitching a ride in the bloodstream.