Cannabis for Postherpetic Neuralgia: What the Evidence Shows
Postherpetic neuralgia (PHN) is persistent nerve pain that remains after a shingles rash has healed. It may feel burning, stabbing, or aching, and even light contact from clothing or a bedsheet can trigger pain. The condition usually affects the same area as the original rash and is more common—and often more severe—in older adults. The Centers for Disease Control and Prevention describes PHN as pain lasting more than 90 days after shingles begins.
Cannabis-based medicines have been studied as possible treatments for chronic neuropathic pain, the broad category that includes PHN. However, the evidence does not show that cannabis is an established treatment specifically for postherpetic neuralgia. The 2018 Cochrane review included 16 studies involving 1,750 people, but the trials covered several types of neuropathic pain rather than PHN alone. The researchers concluded that the potential benefits might be outweighed by adverse effects and that the evidence was limited.
A later Cochrane update reached similarly cautious conclusions: there is no clear evidence that THC-dominant or CBD-dominant cannabis medicines reliably produce at least 50% pain relief, and the certainty of the available evidence remains low or very low. These findings suggest that some patients may experience short-term benefit, but they do not establish cannabis as a proven or first-line therapy for PHN.
One small study is sometimes cited in support of topical cannabinoid treatment. In the 2010 report on topical therapy for facial PHN, eight patients used a cream containing N-palmitoylethanolamine, a compound related to the body’s endocannabinoid system. Five participants reported substantial pain reduction, and the treatment was well tolerated. Because the study was open-label, involved only eight people, and did not use a placebo comparison, its results should be considered preliminary. It also tested a specific topical compound—not standard medical cannabis—and cannot demonstrate that cannabis creams work for PHN generally.
Another relevant study was a randomized, double-blind, placebo-controlled crossover trial of 39 people with treatment-resistant central or peripheral neuropathic pain. The 2013 vaporized-cannabis study compared placebo with cannabis containing 1.29% or 3.53% THC. Both active doses reduced pain more than placebo during the short experimental sessions, and the lower dose was about as effective as the medium dose. The study did not focus specifically on PHN, did not measure long-term effectiveness, and also assessed psychoactive and neuropsychological effects. Its findings therefore provide evidence about short-term neuropathic pain relief—not proof that vaporized cannabis treats postherpetic neuralgia safely over months or years.
Standard PHN treatments include medicines for nerve pain, such as gabapentin, pregabalin, amitriptyline, or duloxetine, along with localized treatments such as lidocaine or capsaicin. The NHS overview of PHN treatments notes that medication choice depends on pain severity, location, other health conditions, and side effects. Cannabis products may interact with other medicines and can cause dizziness, drowsiness, impaired concentration, or other unwanted effects. In the United States, the Food and Drug Administration has not approved cannabis for treating PHN or any other disease, although it has approved certain prescription cannabinoid-related medicines for specific conditions.
Preventing shingles remains the most reliable way to reduce the risk of PHN. The CDC recommends the two-dose Shingrix vaccine for adults age 50 and older and for adults age 19 and older who are immunocompromised. In clinical trials, Shingrix reduced the risk of PHN by about 91% in adults age 50 and older. Anyone with persistent pain after shingles should discuss treatment options with a health care professional rather than relying on unregulated cannabis products or delaying proven care.
