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Consider it a testament to the ubiquity and flexibility of the endocannabinoid system: we can inhale medicinal cannabinoids via combustion or vaporization; ingest them via food or drink; and absorb them directly through the skin, the body\u2019s largest organ.<\/p>\n
This latter category is broader and more complex than many of us give it credit for. Inside the mouth, it includes both buccal (between the gums and cheek, as with a lozenge) and sublingual (under the tongue, as with a tincture) modes of absorption.<\/p>\n
Everywhere else, it includes two additional routes that work in very different ways: topically, via cannabinoid receptors and secondary targets including TRP (\u201ctrip\u201d) channels, PPARs (nuclear receptors), and serotonin receptors that are expressed widely<\/a> in skin cells and superficial tissues; and transdermally, by entering the bloodstream through the skin.<\/p>\n Traditional topicals \u2013 including water-based lotions and creams and oil-based balms and salves \u2013 offer a quick onset time, no psychoactivity, and the potential to treat not only aches, pains, and inflammation, but also skin conditions like psoriasis and eczema. On the other hand, they\u2019re short-acting, relatively low in bioavailability, and limited to the area to which they\u2019re applied.<\/p>\n Transdermal or \u201cskin-crossing\u201d formulations, meanwhile, are systemic. They act on the entire body (and thus may produce mild psychoactivity if THC is involved); they also last longer, and take effect more slowly. Such products rely on chemical enhancers (called \u201cexcipients\u201d) like ethanol, propylene glycol, oleic acid, and even terpenes to help cannabinoids sneak past the skin barrier and into the bloodstream. They also employ special delivery systems like adhesive patches, hydrogels, and nano-emulsions.\u00a0<\/p>\n Of course, what matters most to patients and clinicians is whether topical and transdermal cannabinoids really work. Much of the research to date has focused on testing cannabidiol or CBD\u2019s ability to treat various forms of pain through a variety of molecular mechanisms \u2013 either locally, as with arthritis, muscle soreness, or inflammatory skin conditions; or systemically, for chronic ailments requiring a more controlled and sustained release.<\/p>\n So what do the studies say?<\/p>\n A May 2024 article in the International Journal of Molecular Sciences<\/em><\/a> assesses efforts thus far using CBD to treat inflammatory pain (such as in arthritis) via transdermal delivery systems. It reviews about half a dozen such studies, plus another ten looking at transdermal CBD for other conditions, including drug addiction, neurodegeneration, skin cancer, wound healing, and epilepsy.<\/p>\n Though the Canada-based authors conclude that transdermal delivery of CBD \u201cshows great promise\u201d and represents \u201ca potential novel treatment for chronic inflammatory pain,\u201d they also acknowledge that the jury is still out on its ability to achieve that key benchmark of offering \u201ctangible clinical benefits.\u201d<\/p>\n \u201cA lot of work remains to be done,\u201d they write.<\/p>\n About nine months earlier, another review by a team of Thai researchers appeared in the journal Cannabis and Cannabinoid Research<\/em><\/a> . In this case, the focus was on both topical (local) and transdermal (systemic) formulations. The authors identified a total of just eight studies that met their criteria. Ultimately, they concluded that the available data on pain and other outcomes was unreliable, with a high risk of bias. \u201cNew clinical trials are urgently needed,\u201d they repeat in a familiar refrain.<\/p>\n In our own literature review, Project CBD identified four newer studies that were not included in the abovementioned reviews. Three address strictly topical\/local formulations and one addresses a transdermal formulation. The findings are mixed.<\/p>\n A July 2024 article in Cannabis and Cannabinoid Research<\/em><\/a> <\/em> Next the researchers administered questionnaires and a few exercise tests to ascertain muscle soreness and physical performance. Their findings after three days of repeating the protocol? Placebo recipients reported the most recovery and relief, while the CBD cream appeared to have no significant effects.<\/p>\n A 2022 paper in The<\/em> Journal of Arthroplasty<\/em><\/a> <\/em> On postoperative days 0, 1, 2, 7, 14, and 42, researchers with Thomas Jefferson University in Philadelphia collected data on patient pain, sleep, and opioid use. But upon analyzing the data, they found no significant relationship between CBD use and any of these outcomes.<\/p>\n However, other studies from the last few years have come to opposite conclusions. For example, a phase-two double-blinded, randomized, controlled trial of topical CBD for the treatment of arthritis of the thumb, written up in the Journal of Hand Surgery<\/em><\/a> in July 2022 underscores CBD\u2019s analgesic potential.\u00a0<\/p>\n Treatment with topical CBD led to significant improvements in a variety of self-reported measures including pain and disability.<\/strong><\/p>\n<\/blockquote>\n\n University of Virginia researchers randomized 18 participants to receive a twice-daily treatment of either shea butter alone or shea butter with CBD. After a one-week washout period, participants switched groups. This time the results indicated that treatment with topical CBD led to significant improvements in a variety of self-reported measures including pain and disability.<\/p>\n Finally, a May 2024 article in Scientific Reports<\/em><\/a> Self-reported pain ratings significantly declined over time. Self-reported fatigue, stiffness, and anxiety all improved. And grip strength as measured by a Bluetooth-connected squeeze ball increased. During a subsequent one-week washout phase, pain and grip strength reverted back towards baseline.<\/p>\n \u201cTransdermal CBD gel may have a beneficial effect on pain and grip strength in participants with symptomatic hand osteoarthritis, but requires further exploration,\u201d the authors conclude. \u201c[Future] research should incorporate a double-blind, randomized study design with greater participant numbers and more comprehensive pharmacokinetic and biomarker analysis.\u201d<\/p>\n Nate Seltenrich, Project CBD contributing writer, is the author of the column\u00a0<\/em>Bridging the Gap<\/em><\/strong><\/a>.\u00a0An independent science journalist based in the San Francisco Bay Area, he covers\u00a0a wide range of subjects, including environmental health, neuroscience, and pharmacology.<\/em><\/p>\n Project CBD feedback request: Have you used a CBD-rich topical product? What\u2019s been your experience?<\/em><\/strong> Let us know<\/a><\/p>\n References:<\/p>\n 1.\u00a0Lefebvre, \u00c8.; Tawil, N.; Yahia, L. Transdermal Delivery of Cannabidiol for the Management of Acute Inflammatory Pain: A Comprehensive Review of the Literature.\u00a0Int. J. Mol. Sci.<\/em>\u00a02024<\/strong>,\u00a025<\/em>, 5858. https:\/\/doi.org\/10.3390\/ijms25115858<\/a><\/p>\n 2. \u00a0Scholfield, CN; Waranuch, N; Kongkaew, C. Systematic Review on Transdermal\/Topical Cannabidiol Trials: A Reconsidered Way Forward<\/a> Cannabis and Cannabinoid Research\u00a02023\u00a08:4,\u00a0589-602<\/p>\n 3. \u00a0Pastina JT, Abel, MG, Bollinger, LM, Best, SA. Topical Cannabidiol Application May Not Attenuate Muscle Soreness or Improve Performance: A Randomized, Double-Blinded, Placebo-Controlled Pilot Study. Cannabis and Cannabinoid Research 9 July 2024, \u00a0https:\/\/doi.org\/10.1089\/can.2024.001<\/a><\/p>\n 4. \u00a0Haffar, Amer et al., Topical Cannabidiol (CBD) After Total Knee Arthroplasty Does Not Decrease Pain or Opioid Use: A Prospective Randomized Double-Blinded Placebo-Controlled Trial, Journal of Arthroplasty, Volume 37, Issue 9, 1763 \u2013 1770<\/p>\n 5. \u00a0Heineman, John T. et al. A Randomized Controlled Trial of Topical Cannabidiol for the Treatment of Thumb Basal Joint Arthritis. Journal of Hand Surgery, Volume 47, Issue 7, 611 \u2013 620<\/p>\n 6.\u00a0Bawa, Z., Lewis, D., Gavin, P.D.\u00a0et al.<\/em>\u00a0An open-label feasibility trial of transdermal cannabidiol for hand osteoarthritis.\u00a0Sci Rep<\/em>\u00a014, 11792 (2024). https:\/\/doi.org\/10.1038\/s41598-024-62428-x<\/a><\/p>\nAdvantages and disadvantages<\/strong><\/h2>\n
Clinical benefits?<\/strong><\/h3>\n
Literature review\u00a0<\/strong><\/h3>\n
A killer app for pain?<\/strong><\/h3>\n
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