Study clarifies ginkgo's pain-reducing effects

Experiments in rats show that a standardized ginkgo extract—injected either into the spinal canal or directly into the injured area—effectively reduces inflammation and some types of pain, according to a report in the May issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

The ginkgo biloba extract EGb 761 reduces abnormal responses to heat pain (thermal hyperalgesia), with an effect similar to that of a commonly used pain reliever, reports the study by Sharron Dolan, Ph.D., and colleagues of Glasgow Caledonian University, U.K. They write, "These studies indicate that EGb 761 may offer therapeutic benefit for the treatment of postinjury-associated thermal hyperalgesia and acute inflammation."

Study Clarifies Ginkgo's Pain-Reducing Effects
The researchers used a standard technique to induce pain and inflammation in the paws of rats. They then compared the effects of treatment with EGb 761, a standardized gingko formulation; and diclofenac—a nonsteroidal anti-inflammatory drug (NSAID) commonly used to treat arthritis and other painful conditions. These treatments were given in two different ways: local injection into the paw and central (intrathecal) injection into the spinal canal.

At both injection sites, EGb 761 had significant pain-reducing effects. In reducing thermal hyperalgesia, it was just as effective as diclofenac. The ginkgo extract effectively reduced swelling in the paw swelling, even when injected into the spinal canal.

EGb 761 had no effect on abnormal responses to mechanical stimuli, such as a pinprick (mechanical hyperalgesia). Diclofenac did reduce mechanical hyperalgesia.

In previous animal studies, oral treatment with EGb 761 has shown significant analgesic (pain-reducing) and anti-inflammatory effects. The new study was designed to clarify how these effects occur by comparing the effects of local (paw) and central (spinal canal) injection of EGb 761.

The results show that both local and central administration of ginkgo extract reduce inflammation and thermal hyperalgesia, with effects similar to those of a standard NSAID. The findings lend new insights into the specific pain pathways affected by ginkgo.

The study also adds to the evidence suggesting that gingko extracts could play a useful role in treating some types of inflammatory pain. More study is needed to further clarify how EGb 761 works, and to demonstrate the full range of its treatment and adverse effects.