Kratom is not an MAOI. Its alkaloids do not inhibit monoamine oxidase, the enzyme that MAOIs target. The confusion likely stems from the fact that kratom can still contribute to serotonin syndrome and has dangerous interactions with antidepressants, which are risks people typically associate with MAOIs. But the mechanism behind these risks is different.
How Kratom Actually Works in the Brain
Kratom’s primary alkaloid, mitragynine, is a partial agonist at mu-opioid receptors, the same receptors targeted by opioid painkillers. It also binds to several adrenergic receptors (alpha-1A, 1B, 1D, and alpha-2C), which influence blood pressure and alertness. This is why kratom can feel both stimulating at low doses and sedating at higher ones.
Two other major kratom alkaloids, speciogynine and paynantheine, bind with high affinity to serotonin receptors (specifically the 5-HT1A and 5-HT2B subtypes). Mitragynine itself has weak serotonin receptor binding, but these companion alkaloids are present in meaningful amounts in kratom leaf. This serotonin activity is one reason kratom can cause problems when combined with other drugs that raise serotonin levels, even though it doesn’t do so through MAO inhibition.
Why Kratom Still Poses Serotonin Risks
MAOIs cause serotonin syndrome by preventing the breakdown of serotonin in the brain. Kratom doesn’t do this. Instead, it creates risk through two different pathways: direct activity at serotonin receptors and interference with how your body processes other drugs.
Mitragynine is a potent inhibitor of CYP2D6, a liver enzyme responsible for metabolizing many common antidepressants, antipsychotics, and other psychiatric medications. It also acts as a time-dependent inhibitor of CYP3A, another major drug-metabolizing enzyme. When kratom blocks these enzymes, medications that are normally cleared from the body at a predictable rate can build up to dangerous levels in the bloodstream. A study in the Journal of Pharmacology and Experimental Therapeutics estimated that even a modest 2-gram dose of kratom could increase blood levels of a CYP3A-processed drug by nearly six-fold.
This enzyme inhibition, not MAO inhibition, is the primary way kratom precipitates serotonin syndrome. If you’re taking an SSRI, SNRI, or other serotonergic medication, kratom can cause those drugs to accumulate far beyond their intended concentration. The result can mimic what happens with an MAOI interaction, but the underlying cause is pharmacokinetic (how the drug is processed) rather than pharmacodynamic (how the drug acts on brain chemistry).
Serotonin Syndrome Cases Involving Kratom
Published case reports illustrate this risk clearly. In one case, a 36-year-old man taking venlafaxine (an SNRI) and quetiapine alongside roughly 90 grams of kratom per day developed serotonin syndrome and heart rhythm abnormalities. Clinicians attributed the reaction to kratom inhibiting the CYP2D6 and CYP3A enzymes that normally metabolize those medications, causing them to accumulate.
In another case, a 63-year-old man was taking five serotonergic medications (bupropion, buspirone, desvenlafaxine, trazodone, and ziprasidone) along with kratom. He arrived at the emergency department with a fever of 106°F, confusion, facial drooping, hyperreflexia, clonus, and tremors. His symptoms initially looked like a stroke. Once serotonin syndrome was recognized, treatment with cyproheptadine (a serotonin-blocking drug) rapidly improved his confusion, speech problems, and facial symptoms.
These cases don’t prove kratom alone causes serotonin syndrome. In each instance, other serotonergic drugs were involved. But kratom appears to act as an amplifier, pushing those drugs to toxic levels by slowing their metabolism and adding its own serotonin receptor activity on top.
No Tyramine Reaction Risk
One practical consequence of kratom not being an MAOI: it does not carry the classic dietary restrictions associated with MAOIs. Traditional MAOIs prevent the gut and liver from breaking down tyramine, an amino acid found in aged cheeses, cured meats, fermented foods, and certain wines. Eating high-tyramine foods while on an MAOI can trigger a dangerous spike in blood pressure called a hypertensive crisis. No published evidence links kratom to this type of reaction, which is consistent with its lack of MAO-inhibiting activity.
Why the Distinction Matters
Knowing that kratom is not an MAOI doesn’t make it safe to combine with psychiatric medications. In some ways, its CYP450 enzyme inhibition creates a broader and less predictable set of drug interactions. MAOIs interact with a well-known list of substances, and prescribers can plan around them. Kratom’s enzyme-blocking effects are dose-dependent, vary between individuals, and affect multiple drug classes, including opioids, benzodiazepines, antidepressants, antipsychotics, and antihistamines.
The FDA has not approved kratom for any medical use, and the agency has specifically called for more research into its safety profile when combined with other drugs. Because kratom is sold as an unregulated botanical product, the alkaloid content varies significantly between brands, batches, and preparation methods. This makes predicting its interaction potential with any given medication especially difficult.