San Francisco has recorded its first fatal overdose tied to MGM-15, a potent synthetic opioid derived from kratom that has been turning up in mislabeled herbal supplements sold at smoke shops and gas stations. The San Francisco Office of the Chief Medical Examiner detected the compound in an adult who died in late September, and toxicology testing found MGM-15 both in the person's body and in the packaging of the product they had consumed.
According to KRON4, the product involved was branded “Script Botanical x Maui labs.” The San Francisco Department of Public Health, which issued the health alert via a SF Public Health post, says ingesting too much MGM-15 can result in a fatal opioid overdose. The department also says the Drug Enforcement Administration has designated MGM-15 a Schedule I substance, making it illegal to sell.
The station's report notes that MGM-15 has been found in products marketed as Uncaria tomentosa, commonly known as cat's claw, which are sold for sale in smoke shops and gas stations. Per the same account, the drug had previously been linked to overdoses in Utah and Washington before this case. MGM-15 is not approved for any medical use, according to the same source.
How a Jungle Herb Became an Opioid Risk
MGM-15 is not kratom itself but a semi-synthetic compound built from it. Researchers writing in a study published by Wiley Analytical Science Journals describe MGM-15 as a synthetic derivative of 7-hydroxymitragynine developed through medicinal chemistry efforts, and note it shows greater binding affinity to human mu-opioid and delta-opioid receptors than that parent compound. The same study found MGM-15 is currently sold in the United States for human consumption as a so-called research chemical in tablet form, despite the absence of any described human studies or FDA approval.
A safety alert from the Washington Poison Center warns that MGM-15 and a related compound, mitragynine pseudoindoxyl, are semi-synthetic compounds created in labs, and that taking too much of these substances can slow or stop breathing, while regular use can lead to physical dependence and severe withdrawal symptoms. The alert says recent investigations into products labeled as Cat's Claw have turned up undisclosed 7-hydroxymitragynine, MGM-15, mitragynine pseudoindoxyl, and other potent kratom-derived compounds, sold in vape shops, gas stations, convenience stores, and online. The Utah Poison Control Center has reported four confirmed deaths in Utah involving cat's claw products.
Part of a Shifting Overdose Landscape in San Francisco
The MGM-15 death comes as San Francisco has also confirmed its first overdose death linked to a separate synthetic opioid, cychlorphine, described as more potent than fentanyl, according to the San Francisco Examiner. The paper reports at least 25 overdose deaths nationwide have been linked to cychlorphine as of January, including three in California. It also notes that San Francisco recorded 148 overdose deaths between January and March this year, down from 199 during the same stretch last year and 204 in 2024.
The emergence of new, unregulated synthetic opioids adds another layer of risk to a crisis that has already proven deadly in the city. If someone cannot be awakened, call 911 and administer naloxone if available. The San Francisco Department of Public Health also offers connections to treatment programs and addiction specialists for those struggling with opioid use disorder, and can be reached for treatment help at 888-246-3333.
