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Dr. Todd S. Anhalt
“When you walk into places like CVS or Walgreens, you see lots of displays for CBD creams and oils,” Todd S. Anhalt, MD, said during the annual meeting of the Pacific Dermatologic Association. “The problem is, we don’t know what’s in them or who made them or how good they are. That’s going to be a problem for a while.”
According to Dr. Anhalt, clinical professor emeritus of dermatology at Stanford (Calif.) University, there are about 140 active cannabinoid compounds in cannabis, but the most important ones are THC and cannabidiol (CBD). There are three types of cannabinoids, based on where the cannabidiol is produced: endocannabinoids, which are produced in the human body; phytocannabinoids, which are derived from plants such as marijuana and hemp; and synthetic cannabinoids, which are derived in labs.
Dr. Anhalt described the endocannabinoid system as a conserved network of molecular signaling made of several components: signaling molecules (endocannabinoids), endocannabinoid receptors (CB-1 and CB-2), enzymes, and transporters. There is also overlap between cannabinoids and terpenes, which are responsible for flavor and aroma in plants and marijuana and can enhance the effects of CBD.
“For the most part, CB-1 receptors are in the central nervous system and CB-2 [receptors] are mostly in the periphery,” including the skin and digestive system, said Dr. Anhalt, who practices at the California Skin Institute in Los Altos, Calif. “This is interesting because one of the main conditions I recommend cannabidiol for is in patients with peripheral neuropathy, despite the fact they may be on all sorts of medications such as Neurontin and Lyrica or tricyclic antidepressants. Sometimes they don’t get much relief from those. I have had many patients tell me that they have had reduction of pain and increased functionality using the CBD creams.” CB-2 receptors, he noted, are located in keratinocytes, sensory receptors, sweat glands, fibroblasts, Langerhans cells, melanocytes, and sebaceous glands.
Recent research shows that the endocannabinoid system is involved in modulation of the CNS and in immune function, particularly skin homeostasis and barrier function. “We know that barrier function can be affected by the generation of oxidative species,” he said. “The stress that it causes can decrease barrier function and lead to cytokine release and itch. CBDs have been shown to enter cells, target and upregulate genes with decreased oxidation and inflammation, and protect membrane integrity in skin cells. Therefore, this might be helpful in atopic dermatitis.” Other potential uses in dermatology include wound healing, acne, hair growth modulation, skin and hair pigmentation, skin infections, psoriasis, and cutaneous malignancies, as well as neuropathic pain.
Evidence is strongest for neuropathic pain, he said, which is mediated by CB-1 receptors peripherally, followed by itch and atopic dermatitis. The authors of a 2017 systematic review concluded that “low-strength” evidence exists to suggest that cannabis alleviates neuropathic pain, with insufficient evidence for other types of pain.
Topical CBD comes in various forms: oils (usually hemp oil), creams, and lotions, Dr. Anhalt said. “I advise patients to apply it 2-4 times per day depending on how anxious or uncomfortable they are. It takes my patients 10 days to 2 weeks before they notice anything at all.”
For atopic dermatitis, it could be useful “not to use it instead of a moisturizer, but as a moisturizer,” Dr. Anhalt advised. “You can have a patient get big jars of CBD creams and lotions. They may have to try a few before they find one that they really like, but you can replace all of the other moisturizers that you’re using right now in patients who have a lot of itch.”
As for CBD’s effect on peripheral neuropathy, the medical literature is lacking, but some studies show low to moderate evidence of efficacy. For example, a Cochrane Review found that a 30% or greater pain reduction was achieved by 39% of patients who used cannabis-based treatments, vs. 33% of those on placebo.
“I would not suggest CBD as a first-line drug unless it’s very mild peripheral neuropathy, but for patients who are on gabapentin who are better but not better enough, this is an excellent adjunct,” Dr. Anhalt said. “It’s worth trying. It’s not too expensive and it’s really safe.”
The application of topical CBD to treat cutaneous malignancies has not yet shown evidence of significant efficacy, while using CBDs for acne holds promise. “The endogenous cannabinoid system is involved in the production of lipids,” he said. “Cannabinoids have an antilipogenic activity, so they decrease sebum production. CBD could help patients with mild acne who are reluctant to use other types of medications. For this and other potential dermatologic applications, lots more studies need to be done.”
Dr. Anhalt reported having no financial disclosures.