NIDA Review Finds Kratom Case Reports “Inadequate”

A case report is a detailed medical report of the symptoms, diagnoses, and treatment of an individual patient who presents to a healthcare professional. Case reports are an important part of evaluating the risks of psychoactive substances new to Western medicine, including possible toxicity, drug interactions, and effects on individuals with certain pre-existing conditions.

With the absence of human clinical trials, case reports have made up the bulk of clinical data on kratom. Being that those who experience manageable benefits from kratom use have no reason to see a doctor about it (and often don’t wish to share because of stigma), case reports tend to bias toward negative experiences.

A recently published review (Feldman et al., 2023) funded by the National Institute on Drug Abuse (NIDA) Intramural Research Program found kratom case reports lacking a complete and consistent picture of the patient’s kratom use. The review, “Omissions, Ambiguities, and Underuse of Causal Assessment Tools: a Systematic Review of Case Reports on Patients Who Use Kratom” appeared in Current Addiction Reports on March 2, 2023.

Summary We found considerable variation in reported information and in the thoroughness of the case reports. Reports
tended to be inadequate in full assessment of the patient’s kratom use. As kratom use continues to increase in the USA,
consistent and detailed reporting, usage of biospecimen testing and kratom product assays, consultation of experts to aid
with patient workup, usage of causality assessment tools, and acknowledgement of limitations will improve the quality of
case reports.

(Feldman et al., 2023)

Cells in the below table show reported (white), and unreported, incomplete, or unknown data (red, yellow, orange respectively).

“Fig. 2 Color-coded table… showing degree of completeness of data for each publication included in this review” (Feldman et al., 2023)

Out of 52 case reports/case series reviewed, and 67 patients examined, there were only five instances where kratom products were tested. Kratom was adulterated/contaminated in three cases: hydrocodone/morphine (both in one product), phenylethylamie (a stimulant), and cadmium (a metal that can be toxic if present in high amounts). The brand of kratom was not reported in nearly all cases. The dose of kratom ingested “was not reported or unclear for 31 patients”.

Forty-two patients were screened for the presence of other drugs, and 24 were negative for non-kratom substances. In the remaining cases (over one third of patients), the presence of other substances could not be ruled out, and, as the authors note, many kratom consumers are polysubstance users.

Liver injury was reported in 24 patients, seizure in 19, kidney injury in 9, rhabdomyolysis (“the breakdown of muscle tissue that leads to the release of muscle fiber contents into the blood” – Medline) in 6, and “suspected overdose” in 6. However, according to the authors, given the variation in alkaloid profile and contamination/adulteration in kratom products, linking symptoms to a cause is difficult “when product information is absent or incomplete, as it was for nearly half of the patients described in the reports we reviewed.”

Authors also noted the lack of usage of causality-assessment tools to determine whether kratom or some other cause led to symptoms.

Causality-assessment tools are particularly useful in cases involving drug-induced liver injury, which can be difficult to diagnose and typically relies on exclusion of other conditions that could mimic the injury.. In this sample, a standardized causality-assessment tool was used in the diagnosis of only 4 patients across 4 different case reports and in only 3 out of 24 diagnoses of liver injury in patients who used kratom.

(Feldman et al., 2023)

The authors concluded by urging those who read kratom case reports to consider bias, and for those who write them to include patient use histories, to screen patients and test kratom products for the presence of non-kratom substances, consult experts, use causality assessment tools, and to disclose the absence of any information.


Feldman, J.D., Schriefer, D., Smith, K.E. et al. Omissions, Ambiguities, and Underuse of Causal Assessment Tools: a Systematic Review of Case Reports on Patients Who Use Kratom. Curr Addict Rep (2023).

More information on kratom case reporting

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