A new treatment is in being studied for fibromyalgia (FM) that delivers medication through a skin patch. The drug candidate is called ZYN001 and is under development by Zynerba Pharmaceuticals, based in Devon, Pennsylvania. ZYN001 contains a prodrug medication that the body converts to tetrahydrocannabinol (THC), the active ingredient in marijuana.

Fibromyalgia is a painful disorder that healthcare providers have sometimes failed to recognize as an actual medical condition. Characterized by extreme fatigue and chronic pain, often in localized body regions, fibromyalgia can be hard to distinguish from conditions like arthritis. An estimated 5.6 million individuals in the United States suffer from fibromyalgia.

Once oral medications are absorbed by the gastrointestinal system, they can be present at variable levels in the blood, and may be broken down to some extent in the liver. This is called “first-pass” metabolism. Skin (transdermal) patches could potentially bypass some of these problems.

According to Zynerba Pharmaceuticals, because ZYN001 comes in a patch form it may supply the drug in a more consistent manner than an oral medication. This could allow for fewer psychological effects that are normally associated with THC, since the patch formulation does not permit a peak blood level of THC.

So far, Zynerba has investigated ZYN001 in animal models, as reported on their website. The studies examined the use of subcutaneous medication in rats to assess blood levels of the medication and to examine safety for respiratory symptoms. In a rat pharmacokinetic (blood level) study, researchers noted that ZYN001 “crosses the blood-brain barrier more easily than THC, and low levels in plasma may reduce the likelihood that patients will experience treatment-emergent psychotropic effects.” The blood-level effects will need to be evaluated further in human subjects, however.

A study of respiratory effects in rats found that ZYN001 appeared to be safe, noting “ZYN001 produced no significant changes in the three core measures of respiratory dynamics.” Respiratory depression can be a common side effect of opiate medications, which are commonly used to treat painful conditions, including fibromyalgia.

Many physicians are reluctant to recognize or manage fibromyalgia, which has only recently been recognized by the medical community. New, effective, and safe methods for relieving fibromyalgia are needed. The ZYN001 patch may add to the possible treatments for fibromyalgia. But there are downsides to dermal medications, including skin reactions at the patch site, stigma associated with wearing a patch, and delayed onset of medication delivery compared to oral medications.

ZYN001 is also under study for neuropathic pain, which refers to pain from nerve or central nervous system damage.