New JPET Study: Mitragynine Stimulates Breathing While 7-OH Suppresses It—Opposing Respiratory Effects Explained

Why it matters

This research helps explain why kratom is considered less lethal than classic opioids in terms of overdose risk—while also clarifying why products concentrated in 7-OH are dramatically more dangerous, a distinction critical for clinicians, regulators, and consumers.

The big picture

Respiratory depression—the fatal slowing of breathing—is the primary mechanism of opioid overdose death. For years, kratom was thought to be safer because it appeared to cause less respiratory depression than classical opioids. However, the rapid emergence of 7-OH-enriched products has challenged that assumption. This paper, published in JPET's May 2026 issue, provides mechanistic insight into why the two principal kratom alkaloids have opposite effects on respiration.

Key findings

• Mitragynine (MG), kratom's most abundant alkaloid, unexpectedly increases respiratory frequency—an atypical, stimulatory response not seen with classical opioids.
• 7-hydroxymitragynine (7-OH) induces dose-dependent respiratory depression similar to morphine and other classical opioids.
• The opposing respiratory profiles mean a product's danger depends heavily on its alkaloid ratio and concentration.
• Traditional kratom leaf has relatively low 7-OH content; semi-synthetic and concentrated 7-OH products have far higher levels and thus higher overdose risk.
• The study appears in The Journal of Pharmacology and Experimental Therapeutics (Vol. 393, Issue 5, May 2026) by Wells, Paul, Ramos-Gonzalez, and Majumdar.

What they say

According to the authors, the findings reveal that "MG unexpectedly increases respiratory frequency, and 7-OH induces dose-dependent respiratory depression, similar to classical opioids"—highlighting the urgent need to distinguish between kratom alkaloid profiles in safety assessments.

Bottom line

Kratom's opposing respiratory effects—stimulation from mitragynine, suppression from 7-OH—explain why concentrated 7-OH products carry overdose risks far exceeding those of traditional kratom leaf.