A long-awaited kratom clinical study conducted by the U.S. Food and Drug Administration (FDA) has been published in the Journal of Clinical Psychopharmacology. The pilot study (defined as “a preliminary investigation designed to test the feasibility and design of a larger, more comprehensive study”) involved healthy adult participants who were administered an ascending dose of plain leaf kratom in capsules from a single source to be consumed in a five-minute period. There were five cohorts with eight participants each, for a total of 40 participants. Six of the participants per cohort received kratom, and 2 received a placebo.
According to the abstract:
“The starting dose was 1 g and doses of 3, 8, 10, and 12 g were administered after safety reviews after each dose. After dosing, pupillometry and assessments of subjective effects were performed, and blood samples were collected. Safety assessments included adverse events (AE) monitoring, laboratory tests, vital signs, ECG assessments, physical examination findings, and assessment of suicidality.”
No serious adverse events were reported, though as expected, nausea resulted in the atypical higher doses. Most regular consumers of plain leaf kratom do not consume 8, 10, or 12 grams in a short, five-minute period of time.
According to the study, the 12 g dose also “produced increases on several subjective measures including ratings of ‘drug liking.'”
The lead contributor, FDA scientist Chad Reissig, first announced this study via livestream at the Third Scientific Kratom Symposium held at the University of Florida, Lake Nona, in 2024. A contributor to Kratom Science was in attendance along with scientists from around the world, legal experts, and kratom industry representatives.
Dr. Reissig explained that the broader study would start at the end of 2024 and results would be published approximately two years later (end of 2026). The broader study is a Human Abuse Potential (HAP) study on kratom. This is also a randomized, placebo-controlled clinical trial that the FDA uses to determine drug scheduling and requires for New Drug Applications (NDAs).
FDA has been criticized by the American Kratom Association (AKA) and other kratom advocates for leaving outdated information about the dangers of kratom on its official website, prompting local and state kratom prohibitions. In 2025, the FDA announced that it is recommending the Drug Enforcement Administration (DEA) place 7-hydroxymitragynine, but not plain leaf kratom, on its list of Schedule I controlled substances. This signals a shift in policy since 2016, when the FDA made the same recommendation about all kratom. The DEA decided to make kratom Schedule I, but reversed its decision after a grassroots mass movement opposed it.
The entire preliminary single ascending dose study is currently behind a paywall, and therefore blood test and other results are not yet freely available to the public.
Study Citation
Reissig, C. J., Chen, L., Nallani, S. C., Hawkins, E. G., Galati, S., Bonson, K., Kanumuri, S. R. R., McCurdy, C. R., Sharma, A., Setnik, B., Milovan, D., Kelsh, D., & Chiapperino, D. (2026). A Pilot, Dose-Finding, Pharmacodynamic and Pharmacokinetic Study of Orally Administered Botanical Kratom. Journal of clinical psychopharmacology, 10.1097/JCP.0000000000002158. Advance online publication. https://doi.org/10.1097/JCP.0000000000002158