Science
Symptom science
Findings from poison-center surveillance, case reports and related literature. These are associations in published evidence, not a diagnosis checklist.
What the evidence shows
Sedation, coma, loss of consciousness
Proposed mechanism: Mu-opioid agonism in brainstem and cortex
Sleepiness or loss of consciousness reported by poison centers after 7-OH; 38.8% of single-substance 7-OH exposures had serious outcomes, 20.5% hospitalized.
Evidence type: surveillance; case report
Respiratory depression
Proposed mechanism: Mu-opioid effect on brainstem respiratory centers
IV 7-OH depressed breathing 4.5x more potently than morphine in rats; fully reversed by naloxone. Mitragynine alone did not (increased rate). One human case of cardiopulmonary arrest revived with naloxone. Poison centers list trouble breathing.
Evidence type: animal; case report; surveillance
Seizures
Proposed mechanism: Mechanism unclear: adenosine, adrenergic, serotonergic and proconvulsant effects proposed; withdrawal and co-ingestants also implicated
Systematic review: 42 articles screened, 11 included, 20 patients, little toxicology confirmation. Case series of 11 Malaysian users with recurrent seizures. Poison centers list seizures with 7-OH.
Evidence type: case report; surveillance
Myoclonus, tremor, abnormal movements
Proposed mechanism: Not established; opioid neurotoxicity, seizure mimic, withdrawal or toxin co-exposure are hypotheses (hypothesis only, not sourced)
ICU case after kratom product: intermittent generalized myoclonus and perioral twitching, EEG without seizures, resolved in 48 h (other drugs also detected). Neurology abstract: recurrent encephalopathy with abnormal movements in chronic kratom user. Reversible basal ganglia T1 hyperintensity with seizure in another case. No published tic-like case with 7-OH found.
Evidence type: case report
Nausea, vomiting, constipation
Proposed mechanism: Opioid effects on chemoreceptor trigger zone and gut
Somnolence, vomiting and nausea were the most common adverse events in a dose-finding study of leaf kratom up to 12 g. 7-OH and MGPI reduced GI transit in mice.
Evidence type: human trial; surveillance; animal
Tachycardia, hypertension, agitation, sweating
Proposed mechanism: Adrenergic activity of mitragynine; withdrawal; sympathetic activation
Poison centers list rapid heart rate, high blood pressure, agitation, sweating. Regular kratom users had higher odds of sinus tachycardia (OR 8.6).
Evidence type: surveillance; human cross-sectional
QT prolongation, Brugada pattern, ventricular arrhythmia
Proposed mechanism: hERG and sodium channel block (mitragynine IC50 0.3-2.5 uM in vitro)
Reversible Brugada pattern and QTc prolongation after kratom (case); Brugada pattern after chronic high-dose kratom; Brugada unmasked after smoking a kratom cigarette in a young man with a twin sibling's sudden death; VF during sport with kratom and caffeine; VT requiring ECMO. Users' ECGs overall similar to controls except borderline QTc and tachycardia.
Evidence type: in vitro; case report
Liver injury
Proposed mechanism: Idiosyncratic, mostly cholestatic
11 DILIN cases, all jaundiced, median latency 14 days, all recovered; systematic review of 32 cases.
Evidence type: case report; cohort
Hypogonadism, hyperprolactinemia
Proposed mechanism: Opioid suppression of GnRH
One case: low testosterone and raised prolactin normalized in 2 months off kratom. A study of 19 chronic tea users found no testosterone change.
Evidence type: case report; human cross-sectional
Psychosis, delirium, self-harm
Proposed mechanism: Substance-induced psychosis, withdrawal; contribution of co-ingestants
Case titled 7-OH-induced psychosis and delirium; self-amputation with cannabis and kratom products; withdrawal psychosis with 7-OH plus nicotine pouches requiring intubation; suicidal ideation in two 7-OH withdrawal cases.
Evidence type: case report
Insomnia and sleep disruption
Proposed mechanism: Opioid withdrawal; noradrenergic rebound
Sleep difficulty among commonly reported withdrawal symptoms in Malaysian users; insomnia in 7-OH withdrawal case.
Evidence type: survey; case report
Cognition, learning, memory
Proposed mechanism: Not established for 7-OH
No 7-OH human cognitive data retrieved.
Evidence type: none found
Adolescent and developing-brain effects
Proposed mechanism: Not studied for 7-OH or MGPI
Poison centers received 53 7-OH cases from 1 Feb to 30 Apr 2025, 6 in people under 18. Products have child-appealing flavors and packaging (69% of MGPI products). An adolescent medicine commentary calls for screening in vape-shop-exposed youth.
Evidence type: surveillance only
Dependence and tolerance
Proposed mechanism: Mu receptor adaptation
Tolerance within days and severe use disorder within weeks in case reports; rodent self-administration.
Evidence type: case report; animal; survey
Withdrawal (acute)
Proposed mechanism: Noradrenergic rebound after mu agonist removal
Onset within 8 h; COWS peak 14 in one case, 31 in an MGPI case; supportive care resolved acute signs in 72-96 h; precipitated withdrawal after buprenorphine start in one case; rodent withdrawal at least 5 days after mitragynine.
Evidence type: case report; animal
Pulmonary injury (ingested or inhaled)
Proposed mechanism: Hypersensitivity, alveolar hemorrhage, ARDS, secondary hypoxia
Systematic review of 24 reports: diffuse alveolar hemorrhage (3), ARDS (3), eosinophilic pneumonitis (2); all clinical patients survived. No vape-specific data.
Evidence type: case report; forensic series
Overdose death
Proposed mechanism: Respiratory depression, often with other depressants
DEA TOX: 85 cases since 2019 with 7-OH, 55 fatal, median age 36, mean 7-OH 463 ng/mL, often with other drugs. Los Angeles Medical Examiner: 3 fatal 7-OH overdoses with alcohol present. NPDS 2015-2025: 233 kratom-associated deaths, 79% in multi-substance reports. Civil complaint alleges a 36-year-old died after buying 7-OH tablets (allegation only).
Evidence type: surveillance; case report; allegation
Rhabdomyolysis and neurologic deficits after immobilization
Proposed mechanism: Prolonged unconsciousness
A 2026 case report of rhabdomyolysis, renal failure and chronic neurologic deficits after prolonged immobilization from a 7-OH product (abstract not reviewed).
Evidence type: case report
Neonatal withdrawal
Proposed mechanism: Placental transfer of opioid-active alkaloids
Neonatal abstinence syndrome after maternal kratom tea; six case reports reviewed.
Evidence type: case report; systematic review