FDA Researchers Complete First Pilot Pharmacokinetic and Pharmacodynamic Study of Botanical Kratom in Humans

Why it matters

This is the first study in which FDA scientists themselves systematically tested kratom in human volunteers — a major step toward evidence-based regulation that neither dismisses nor exaggerates the plant's risks.

The big picture

Kratom is currently unscheduled federally, but regulatory pressure on its potent derivative 7-OH has intensified. Critics have argued that most kratom safety data comes from case reports or animal studies. This FDA-led clinical trial used botanical kratom leaf with naturally low 7-OH levels, offering the first controlled human pharmacokinetic and pharmacodynamic dose-finding data directly from the agency tasked with regulating it.

Key findings

• Study enrolled 40 recreational polydrug users (6 active, 2 placebo per cohort) given single oral doses of 1 g to 12 g kratom
• No deaths or serious adverse events occurred at any dose
• Kratom caused pupillary constriction at doses of 3 g or more — a classic opioid effect
• The 12 g dose produced elevated drug-liking, euphoria, and high ratings on visual analog scales
• Nausea, vomiting, and somnolence were the most common side effects reported
• Alkaloid concentrations showed generally orderly, dose-related effects

What they say

According to FDA researchers, "Kratom produced some opioid-like effects including pupillary constriction, and the 12 g dose produced effects commonly associated with drugs of abuse such as VAS ratings of drug liking, good effects, and high."

Bottom line

FDA's own clinical study confirms botanical kratom has measurable opioid-like effects at high doses — providing a scientific foundation for regulatory decisions rather than relying solely on case reports.