Acupuncture and Pain Relief: Clinical Trials and Biological Basis

Acupuncture is a popular invasive pain relief application. Acupuncturists insert specialized needles under the patient’s skin (in proximity to the site of pain) and either electrically or manually stimulate the needles. The popularity of acupuncture soared in the US in 1971, when a member of Nixon’s press corps reported the effectiveness of the Oriental system of pain relief using fine needles. Since then, a plethora of clinical trails were conducted to evaluate the effectiveness of acupuncture in pain relief. In the US, the National Institutes of Health recognizes acupuncture as complementary and alternative medicine.

Acupuncture Pain Relief Clinical Trials

The effectiveness of acupuncture as a pain reliever is a subject of debate. There are acupuncture enthusiasts and opponents, and the verdict on the effectiveness of acupuncture as a painkiller depends on their own interpretation. Clinical trails both persuade and dissuade patients on the effectiveness of acupuncture as a pain relief therapy. In clinical trials, in order to establish whether an agent is effective or not, appropriate controls are essential. The results of clinical trails that fail to include appropriate controls are quite misleading. Experts dispute whether the controls used in all acupuncture clinical trials are scientifically valid or not.

There is something called “placebo effect” in clinical trials, which means the beneficial effects observed in a study is not specifically attributable to the agent of interest (in this case, acupuncture). Nonspecific effect is a misleading factor in clinical trials. Proponents of acupuncture usually ignore nonspecific effects and opponents make it a point to underline them. In recent years, in order to reduce the placebo effect, non-penetrating sham-acupuncture devices were developed to use as placebo in acupuncture clinical trials. Most clinical trials using these devices as controls fail to establish an overwhelming effect of acupuncture on pain. However, those who look for a simple and nontoxic means of pain relief would go for a test session.

Biological Basis of Acupuncture Pain Relief

Apart from clinical trials, biological studies looking at the molecular level are also in progress to address how acupuncture relieves pain. Research shows that upon activation by acupuncture needles, the central nervous system releases various signaling molecules such as opioid peptides, glutamate, 5-hydroxytryptamine, and cholecystokinin octapeptide. Among these, the opioid peptides act as key pain modulators of acupuncture.

The quality and quantity of opioid peptides release depends on the frequency of electric impulse exerted on acupuncture needles. For example, at a frequency of 2Hz enkephalin, beta-endorphin and endomorphin are released. At higher frequency of 100Hz dynorphin is released. A combination of two frequencies simultaneously releases all four opioid peptides enabling maximum therapeutic effect of acupuncture pain relief.

Acupuncture Pain Relief and Adenosine

A recent study on mice reports, adenosine, a neuromodulator known to reduce pain, does the trick for acupuncture. The researchers inserted acupuncture needles near the “Zusanli point” in mice, and rotated the needles every five minutes for 30 minutes, and analyzed local release of adenosine.

The authors report in the Nature Neuroscience journal that acupuncture pressure increases the level of adenosine 24-fold. They also report that synthetic drugs that act like adenosine (agonists), faithfully mimic the effects of acupuncture. These experiments were conducted in mice. It needs to be seen how significant this phenomenon is in humans. If further studies reproduce these results and verify that acupuncture pressure releases adenosine, and modulates pain in humans, then new avenues will open for acupuncture therapy.