Adjuvant topical therapy with a cannabinoid receptor agonist in facial postherpetic neuralgia

Postherpetic neuralgia is a frequent adverse event in herpes zoster patients and difficult to treat. Conventional analgetic therapy often fails to reduce the burning pain transmitted by unmyelinated nerve fibers. These nerves express cannabinoid receptors which exert a role in modulation of nociceptive symptoms. Therefore, topical therapy with cannabinoid receptor agonist seems likely to suppress local burning pain.

In an open-labeled trial, 8 patients with facial postherpetic neuralgia received a cream containing the cannabinoid receptor agonist N-palmitoylethanolamine. The course of symptoms was scored with the visual analog scale.

5 of 8 patients (62.5 %) experienced a mean pain reduction of 87.8 %. Therapy was tolerated by all patients. No unpleasant sensations or adverse events occurred.

Topical cannabinoid receptor agonists are an effective and well-tolerated adjuvant therapy option in postherpetic neuralgia.