Is Kratom the New 'Legal High' on the Block?: The Case of an Emerging Opioid Receptor Agonist with Substance Abuse Potential.

Kratom is an unscheduled opioid receptor agonist that comes in the form of dietary supplements currently being abused by chronic pain patients on prescription opioids. Active alkaloids isolated from kratom such as mitragynine and 7-hydroxymitragynine are thought to act on mu- and delta-opioid receptors as well as alpha-2 adrenergic and 5-HT2A receptors. Animal studies suggest that kratom may be more potent than morphine. Consequently, kratom consumption produces analgesic and euphoric feelings among users. In particular, some chronic pain patients on opioids take kratom to counteract the effects of opioid withdrawal. Although the Food and Drug Administration has banned its use as a dietary supplement, kratom continues to be widely available and easily accessible on the Internet at much less expensive rates than some opioid replacement therapies like buprenorphine. There are no federal regulations monitoring the sale and distribution of this drug, yet kratom has been associated with severe signs and symptoms such as hallucinations, delusions, depressions, myalgias, chills, nausea/vomiting, respiratory hepatoxicity, seizures, coma, and death. A search of the pain literature shows past research has not described the use and potential deleterious effects of this drug. Many pain physicians are not familiar with kratom and as providers who take care of high-risk chronic pain patients using prescribed opioids, knowledge of current unregulated opioid receptor agonists with abuse potential is of paramount importance. The goal of this article is to introduce kratom to pain specialists and to spur a conversation on how pain physicians may take the lead to help curb the opioid abuse and overdose epidemic. Further studies may be required to help better understand the clinical and long-term effects of kratom use among chronic pain patients.Key words: Opioid receptor agonist, Kratom, Mitragynine, opioid overdose, chronic pain, substance abuse.