Charles B. Berde, M.D., Ph.D. ASA ANNUAL MEETING

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DALLAS -- The use of local anesthetics to relieve surgical pain often works well but not long enough. Now, a timed-release version of a local anesthetic could help to solve this problem.

Currently, injections of local anesthetics provide pain relief for only four to six hours after surgery, which is not long enough for the pain after most operations. The most commonly used local anesthetic for postsurgical pain relief is the drug bupivacaine. Recently researchers have uncovered a novel approach that allows anesthesiologists to administer a local injection containing microspheres (microscopic particles) of the drug during surgery.

"The microspheres would dissolve slowly and steadily and last several days instead of hours," Charles B. Berde, M.D., Ph.D., a professor of anesthesiology and pediatrics at Harvard Medical School, said. Dr. Berde reviewed recent strides in pediatric postsurgical pain management at the American Society of Anesthesiologists annual meeting.

Timed-release local anesthetics may be particularly important for children, Dr. Berde said, because currently available local anesthetics wear off sooner in children than in adults.

"Bupivacaine happens to have the right chemical properties for making a sustained-release suspension. The drug does not dissolve readily in water, and that makes it relatively easy to produce in microsphere form," Dr. Berde said. This new formulation was developed by Dr. Berde's lab group at Harvard Medical School and Boston Children's Hospital in collaboration with chemical engineers at Massachusetts Institute of Technology.
Dr. Berde and fellow researchers believe that this microsphere method is a particularly useful way to produce a reliable, timed-release pain reliever. The microspheres are small, round particles made up mostly of bupivacaine, along with some tiny strands of a long-chain molecule, known as a polymer, that is absorbed in the body like dissolvable sutures.

The medication would be most useful for operations involving the chest, abdomen or other areas where the patient doesn't mind being numb for several days, he said.

The formulation is currently being tested in adults. If proven to be safe and effective for adults, it will next be examined in children undergoing surgery.

Dr. Berde said he hopes that clinical trials with children will begin within the year.

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