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Diagnostic pitfalls and laboratory test interference after hydroxychloroquine intoxication: A case report.
Joshua B Radke1, Jennie M Kingery2, Jon Maakestad2
1Department of Emergency Medicine, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA, 52242, USA.
Toxicology Reports
|November 2, 2019
Summary
Hydroxychloroquine overdose can cause severe hypokalemia and ECG changes. High urine hydroxychloroquine levels may interfere with drug of abuse screening and other urine assays.
Area of Science:
- Toxicology
- Clinical Pharmacology
- Analytical Chemistry
Background:
- Hydroxychloroquine (HCQ) is used for autoimmune diseases.
- HCQ overdose is rare, with limited data compared to chloroquine.
- Monitoring recommendations often extrapolate from chloroquine overdose experiences.
Observation:
- A case of intentional hydroxychloroquine overdose (12g) in an adolescent.
- Clinical features included hypokalemia and ECG abnormalities (widened QRS/QT).
- Urine hydroxychloroquine concentrations exceeded 500 mg/L, triggering false positives in drug screens.
Findings:
- High urine hydroxychloroquine concentrations (>500 mg/L) are possible after overdose.
- Hydroxychloroquine can cause significant bias or alarms in 6 of 24 urine assays tested.
- Assays affected include qualitative drug screens (buprenorphine, cotinine, oxycodone, THC) and quantitative assays (microalbumin, myoglobin).
Implications:
- Clinicians should be aware of potential laboratory assay interference following hydroxychloroquine overdose.
- Elevated urine hydroxychloroquine levels can lead to false-positive drug test results.
- Further research is needed to understand the full spectrum of analytical interferences from hydroxychloroquine.
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