Magazine article Clinical Psychiatry News

Old Drugs in New Role: Relieving Chronic Pruritus; Cannabinoid Agonists, Opioid Receptor Antagonists Have Attracted the Attention of Dermatologists

Magazine article Clinical Psychiatry News

Old Drugs in New Role: Relieving Chronic Pruritus; Cannabinoid Agonists, Opioid Receptor Antagonists Have Attracted the Attention of Dermatologists

Article excerpt

PARIS -- Cannabinoid agonists and opioid receptor antagonists are among the novel treatments being explored for chronic pruritus, Dr. med. Sonja Stander, reported at the Fourth International Academy of Cosmetic Dermatology World Congress.

Cannabinoid receptors are promising therapeutic targets because they play an important role in a variety of processes, including metabolic regulation, pain, craving, and anxiety. They can be influenced directly by agonists or antagonists, or indirectly through manipulation of the endocannabinoid metabolism.

Two cannabinoid receptors, CB1 and CB2, are the primary targets of endogenous cannabinoids, and are expressed in central and peripheral neurons.

Recent research by Dr. Stander and colleagues at the University Hospital in Munster, Germany, has provided evidence that CB1 and CB2 are also present in abundance in human cutaneous nerve fibers and mast cells (J. Dermatol. Sci. 2005;38:177-88).

"Since cannabinoid receptors are expressed on cutaneous nerve fibers, topical cannabinoid agonists directly inhibit the transmission of pruritus and therefore represent a promising new therapeutic modality," Dr. Stander said.

In a pilot study, 22 patients with chronic pruritus, aged 25-82 years, were treated with one application of a topical cream that contained a cannabinoid receptor agonist.

Itching was significantly reduced in 14 of 22 patients (63.6%), 8 patients were completely healed, and 8 were nonresponders.

Overall the response was very rapid, with patients experiencing relief within 2 days to 2 weeks, she said. The treatment was effective even in patients with a long history of itching.

Opioid receptor antagonists, developed to treat patients with opioid and alcohol dependence, represent another potential treatment. They block opioid receptors in the brain and spinal cord and activate pain-transmitting nerves, which themselves inhibit itch-transmitting neurons. …

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