Mitragynine and 7-hydroxymitragynine: Bidirectional effects on breathing in rats

Area of Science:

• Pharmacology
• Toxicology
• Respiratory Physiology

Background:

• Kratom use is rising for pain and opioid withdrawal, with products often containing 7-hydroxymitragynine (7-HMG).
• Understanding the respiratory effects of kratom alkaloids and naloxone's efficacy is crucial due to potential risks.

Purpose of the Study:

• To evaluate the respiratory depressant effects of 7-HMG and mitragynine (MG).
• To determine if naloxone can reverse these respiratory effects.

Main Methods:

• Respiratory parameters were measured in rats using whole-body plethysmography.
• Drugs (morphine, 7-HMG, MG, naloxone) were administered intravenously.

Main Results:

• 7-HMG and morphine induced significant respiratory depression; 7-HMG was 4.5-fold more potent than morphine.
• MG administration unexpectedly increased respiratory frequency.
• Naloxone reversed respiratory depression from morphine and 7-HMG but not the stimulant effect of MG.

Conclusions:

• 7-HMG exhibits potent opioid-like respiratory depressant effects reversible by naloxone.
• MG demonstrates respiratory stimulant properties via non-opioid pathways.
• Pharmacological differences highlight risks of high-7-HMG kratom and potential safety of MG.