Herb Poisoning Workup

Updated: Jan 12, 2021
  • Author: David Vearrier, MD, MPH; Chief Editor: Michael A Miller, MD  more...
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Approach Considerations

When evaluating critically ill patients with unknown ingestions, a number of laboratory tests should be considered to help identify the possible toxic effects and severity of illness caused by the material ingested. Laboratory tests can include the following:

  • Complete blood count (CBC) and peripheral blood smear - Anemia and basophilic stippling should raise a suspicion of lead contamination/exposure
  • Electrolyte level - Elevated potassium level should raise a suspicion of cardiac glycoside exposure
  • Blood urea nitrogen (BUN) level
  • Creatinine level
  • Glucose level
  • Creatine phosphokinase (CPK or CK) should be obtained in patients with psychomotor agitation or increased musculoskeletal tone to assess for rhabdomyolysis
  • Liver function tests (LFTs)
  • Electrocardiogram (ECG) - To evaluate for evidence of cardiac glycoside effects (bradycardia, AV blocks, suprajunctional rhythms, PR prolongation, "scooping" of ST segment)
  • Urinalysis
  • Urine and serum toxicologic screens (including aspirin and acetaminophen levels)
  • Pregnancy test

Evaluate serum digoxin levels with exposure to plants containing cardiac glycosides, such as Digitalis lanata. Serum digoxin levels in these circumstances reflect exposure only and do not correlate with toxicity (see Cardiac Glycoside Plant Poisoning).

A careful history of herbal products the patient takes is vital not only for identifying direct toxicity but also for guiding therapeutic drug monitoring. For example, multiple herbal products can interfere with digoxin assay results, resulting in either falsely elevated or decreased digoxin serum concentrations.

Use urine drug screens (eg, thin-layer chromatography, gas chromatography, mass spectrometry) to detect adulterants. Ephedra use may be detected as phenylpropanolamine (which was recalled from the US market) or may turn the amphetamine screen on a urine drug screening test positive.

Heavy metal screens may be appropriate with specific clinical presentations. See the following:

Radiographs can assist with diagnosing heavy metal ingestion if opacities are seen with the gastrointestinal tract. Even a radiograph of the herbal product itself may reveal the presence of a heavy metal.

Consider a computed tomography scan of the brain for patients with altered mental status. Consider a lumbar puncture for patients with altered mental status of unclear etiology, especially if fever and/or nuchal rigidity is present.