Pain Management Watch

Capsaicin in Pain Relief Topicals May Act as Carcinogen

The September issue of Cancer Research published a study that raises concerns about capsaicin, an ingredient commonly used in topical creams for pain relief. The study, “Cocarcinogenic Effect of Capsaicin Involves Activation of EGFR Signaling but Not TRPV1,” underscores previous studies that have reported on a connection between capsaicin and skin cancer. Many OTC topical pain remedies contain capsaicin. The authors, Zigang Dong, MD, PhD, of The Hormel Institute, University of Minnesota, and Ki Won Lee, PhD, Department of Bioscience and Biotechnology, Konkuk University, Seoul, report that the molecular mechanisms of the cancer-promoting effects of capsaicin are not clear and the role of this ingredient, widely consumed worldwide, in carcinogenesis is controversial. Their study, however, indicates that capsaicin acts as a carcinogen or cocarcinogen, particularly during the tumor promotion stage. Capsaicin from chili peppers promoted stomach and liver cancer in mice, and epidemiologic studies suggest a positive association between the incidence of stomach cancer and the consumption of chili pepper—rich diets. Capsaicin also increases 12-0-tetradecanoylphorbol-13-acetate– induced cyclooxygenase-2 amounts, which are commonly found in both malignant tissue and tumors, including skin cancer. The authors concluded that capsaicin induces the sustained activation of epidermal growth factor receptor (EGFR) downstream signals, which has implications for “understanding the role of EGFR in capsaicinmediated survival of tumors.”

Medical Marijuana for Neuropathic Pain Relief

Chronic neuropathic pain may be relieved by cannabis, according to a new study at McGill University Health Centre (MUHC) and McGill University in Montreal published in the Canadian Medical Association Journal. Researchers revealed that individuals with chronic neuropathic pain who smoked and inhaled doses of cannabis containing approximately 10% tetrahydrocannabinol (THC) 3 times daily over a period of 5 days reported modest initial pain reduction, improved mood, and better sleep patterns. The patients in the study were not able to control pain symptoms using standard therapies and the onset of pain was a result of injuries to the nervous system due to posttraumatic or postsurgical events.

Noted lead author Mark Ware, MD, director of clinical research at the Alan Edwards Pain Management Unit at MUHC and assistant professor of anesthesia on McGill University’s Faculty of Medicine, “This study marks an important step forward because it demonstrates the analgesic effects of cannabis at a low dose over a short period of time for patients suffering from chronic neuropathic pain.” Larger-scale studies with a longer time frame and higher doses of THC are needed to further evaluate the efficacy and long-term safety of medical cannabis. “Our challenge as researchers is to continue to conduct rigorous clinical studies on the medical use of cannabis with strict attention to details such as quality and dosage,” said Dr. Ware.

Educating Health Care Professionals on Postherpetic Neuralgia

The American Pain Foundation (APF) released the results of a national survey at the American Pain Society Annual Meeting that indicate that most Americans are unaware of the risks and symptoms of postherpetic neuralgia (PHN), or after-shingles pain. The survey also revealed that only one third of these individuals reported being warned by a health care professional about the possibility of developing PHN.

The reawakening of the chickenpox virus affects approximately 1 million people in the United States annually. One in 5 of those who have this condition may develop PHN, the result of nerve damage caused by the shingles rash. The elderly population is most commonly affected by PHN, which is one of the most common causes of pain-related suicide in older Americans. Said Will Rowe, chief executive officer of the APF, “The results of this new survey demonstrate the lack of knowledge about PHN among people who have had shingles.”

Key findings of the survey included that 51% of respondents reported experiencing pain shortly after or within months after their shingles rash went away. More than one half said that the pain they experienced after having shingles was more frustrating than shingles itself. While 60% said their physician mentioned burning, aching, sharp, or itching pain related to the shingles rash, only one third said that their health care provider told them about the possibility of developing PHN.

As a result of the survey, the APF has joined forces with the Patchwork Hope Network to raise awareness of PHN for both the public and health care professionals. Live educational events, training programs for aging and for health care professionals, and an interactive Web site—www.AfterShingles.com— are available to learn more about the condition and its aftereffects.