This page summarizes controlled human studies evaluating kratom (Mitragyna speciosa) and its primary alkaloids, mitragynine and 7-hydroxymitragynine (7-OH).
Included are one FDA-registered clinical research result and peer-reviewed pharmacokinetic investigations examining safety, metabolism, subjective effects, and dose response under controlled laboratory conditions.
This was a randomized, double-blind, placebo-controlled study evaluating single and repeated daily oral doses of dried kratom leaf powder (MitraLeaf) in healthy adult volunteers.
The MitraLeaf product contained <0.01% 7-OH. The paper confirms that 7-OH detected in plasma primarily results from metabolic conversion of mitragynine (via CYP3A4), not from high 7-OH content in the plant material.
No serious adverse events or deaths were reported. Treatment-emergent adverse events (TEAEs) generally increased with higher dose levels.
Most common after single dose:
Most common after 15 daily doses:
Most TEAEs were mild in severity (approximately 90%+). A small number were moderate. Severe events were rare and resolved.
Abuse potential–related adverse events were monitored. Euphoric mood was reported in only three participants total (one in each active single-dose cohort and one in placebo).
No participant reported euphoric mood during the multiple-dose phase after receiving active kratom.
Only one withdrawal-related event (mild diarrhea) was reported during follow-up.
Six participants were withdrawn early:
ALT and AST elevations at the highest dose resolved after stopping dosing. No cases met FDA criteria for drug-induced liver injury (Hy’s Law).
No clinically significant changes were observed in blood pressure, heart rate, respiratory rate, oxygen saturation, or ECG parameters. No QTc prolongation above regulatory concern thresholds was reported.
The study was funded by NP Pharma. The clinical trial was conducted under institutional review board approval. Authors disclosed consultant relationships with the sponsor.
This study measured how mitragynine and 7-hydroxymitragynine (7-OH) appear in blood after a single dose and after repeated daily dosing (15 days) of oral, encapsulated dried kratom leaf powder.
The kratom powder contained very little pre-formed 7-OH (<0.01%), yet measurable 7-OH was still detected in plasma after dosing. This indicates 7-OH exposure largely reflects metabolic conversion of mitragynine inside the body.
Mitragynine showed a long terminal half-life that increased with dose (reported up to ~43 hours after the highest single dose and ~61 hours after repeated dosing in one cohort). 7-OH had a shorter half-life than mitragynine, but also increased with dose and showed variability at higher doses.
With repeated daily dosing, mitragynine accumulation was described as low to moderate, while 7-OH showed minimal accumulation compared with mitragynine.
The study reports it was funded by Johnson Foods, LLC (manufacturer of the MitraLeaf dried kratom leaf powder), and the clinical study was performed by SGS Nutrasource in Ontario, Canada. Authors disclosed consulting relationships with the sponsor.
This study is registered on ClinicalTrials.gov and evaluates single-dose oral kratom administration under controlled laboratory conditions. The results are publicly available in standardized reporting format.
The study enrolled healthy adult volunteers who met predefined eligibility criteria. Participants were screened for medical stability prior to enrollment. The registry does not indicate that this was a chronic-use or dependence study.
According to the ClinicalTrials.gov record, this study was sponsored by the U.S. Food and Drug Administration (FDA). The study was conducted in a controlled clinical research setting under federal oversight.
The ClinicalTrials.gov results page provides structured tables showing dose levels, laboratory measurements, subjective ratings, and safety events. These data characterize short-term pharmacologic effects under supervised conditions.
The study does not evaluate long-term daily use, dependence development, adolescent exposure, or retail product variability.
Controlled human studies of kratom remain limited in number, but the studies summarized here provide structured information on metabolism, short-term tolerability, and measurable subjective effects under supervised conditions.
Controlled trials are designed to measure effects under specific conditions. Surveillance systems (mortality, poison control, adverse event reporting) capture broader real-world patterns and are presented elsewhere on this site.