Anesthetic approach stops pain without affecting motor function

February 1, 2010, Children's Hospital Boston

One of the holy grails of local anesthesia is the ability to achieve a long-lasting nerve block that eliminates pain sensation while not affecting motor function. Now, researchers at Children's Hospital Boston have discovered an anesthetic approach that seems to do just that. If it proves to work in humans as well as it did in rats, it could be useful in a variety of medical applications, providing, for example, a local anesthetic for childbirth that would block pain without interfering with the mother's ability to push, or for musculoskeletal disorders in which it is important to maintain mobility.

The discovery was reported in the online Early Edition of the during the week of February 1.

The researchers, led by Daniel Kohane, MD, PhD, of the Division of at Children's, originally sought only to find an agent that would prolong the anesthetics' effects. They focused on surfactants, a subclass of so-called "chemical permeability enhancers" that enable drugs to spread more easily throughout a tissue.

In testing three kinds of surfactant along with the anesthetics QX-314 and QX-222 (both derivatives of lidocaine), they found that this approach did prolong the sensory block in rats' sciatic nerves, for up to 7 hours or more depending on the surfactant, but didn't prolong ; in some cases the motor block was absent or of very short duration. In the rats, this meant they were able to tolerate having their paws on a hot plate for long periods, yet still able to balance and bear weight on their legs.

"This was a surprise finding," says Kohane, who also directs the Laboratory for Biomaterials and Drug Delivery (LBDD) at Children's. "What we've discovered really is a new approach; the question now is to figure out the mechanism by which it works and look at the effects of other chemical permeability enhancers."

Kohane speculates that surfactant made the anesthetic better able to penetrate sensory nerves, which have little or none of the fatty coating known as myelin, whereas in motor neurons, which have abundant myelin, the active drug gets trapped in the myelin, never entering the nerve itself.

The lab's next steps will be to explore the effects of different permeability enhancers and examine their safety, since at high doses the drug combination could potentially be toxic to the nerves. The eventual plan is to test the approach in larger animals.

A parallel approach to achieving a pain-specific nerve block was proposed in 2007 by Clifford Woolf, MD, PhD, recently appointed director of the Children's Hospital Boston Program in Neurobiology. Woolf's team combined QXT-314 with capsaicin, which opens cellular gates that are only present in sensory neurons, and achieved pain-specific blocks in rats lasting 2 hours or more.

More information: Sagie I and Kohane D. Prolonged sensory-selective nerve blockade. PNAS online early edition, week of February 1, 2010.

Related Stories

Recommended for you

Iron triggers dangerous infection in lung transplant patients, study finds

February 21, 2018
Researchers at the Stanford University School of Medicine have identified elevated tissue iron as a risk factor for life-threatening fungal infections in lung transplant recipients.

Neuroimaging reveals lasting brain deficits in iron-deficient piglets

February 21, 2018
Iron deficiency in the first four weeks of a piglet's life - equivalent to roughly four months in a human infant - impairs the development of key brain structures, scientists report. The abnormalities remain even after weeks ...

Products derived from plants offer potential as dual-targeting agents for experimental cerebral malaria

February 21, 2018
Malaria, a life-threatening disease usually caused when parasites from the Plasmodium family enter the bloodstream of a person bitten by a parasite-carrying mosquito, is a severe health threat globally, with 200 to 300 million ...

Scientists in Germany improve malaria drug production

February 21, 2018
Scientists in Germany who developed a new way to make a key malaria drug several years ago said Wednesday they have come up with a technique to make the process even more efficient, which should increase global access and ...

Early results from clinical trials not all they're cracked up to be, shows new research

February 21, 2018
When people are suffering from a chronic medical condition, they may place their hope on treatments in clinical trials that show early positive results. However, these results may be grossly exaggerated in more than 1 in ...

Clues to obesity's roots found in brain's quality control process

February 20, 2018
Deep in the middle of our heads lies a tiny nub of nerve cells that play a key role in how hungry we feel, how much we eat, and how much weight we gain.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.