American College of Medical Toxicology. ACMT Recommends Against Use of Post-Chelator Challenge Urinary Metal Testing

Trends in Shortages of Lead Chelators From 2001 to 2022

OBJECTIVE

The study aims to describe drug shortages affecting lead chelators in the United States from 2001 through 2022.

METHODS

Drug shortage data were retrieved from the University of Utah Drug Information Service from January 1, 2001, through December 31, 2022. Shortages of first- and second-line lead chelators were analyzed. Drug class, formulation, administration route, shortage reason, shortage duration, generic status, single-source status, and presence of temporally overlapping shortages were examined. Total shortage months, percentages of study period on shortage, and median shortage durations were calculated.

RESULTS

Thirteen lead chelator shortages were reported during the study period. Median duration was 7.4 months and the longest shortage (24.8 months) involved calcium disodium edetate. Calcium disodium edetate and dimercaprol had the greatest number of shortages, 4 each, and 61.5% of shortages involved parenteral medications. Median shortage duration was 14.2 months for parenteral agents and 2.2 months for non-parenteral agents. All shortages involved generic, single-source products. Supply/demand and manufacturing problems were the most common shortage reasons provided. Overlapping shortages occurred for 3.7% of the study period. Median shortage duration increased from 3 to 11 months in the second half of the study period, and 61.5% of shortages occurred in the second half of the study period.

CONCLUSIONS

All chelators experienced multiple shortages, which became increasingly frequent and prolonged over time. Concurrent shortages occurred, potentially hampering substitution between different agents. Health care stakeholders must build supply chain resilience and develop guidelines regarding how to modify chelation therapy based on shortage conditions.

Failure of chelator-provoked urine testing results to predict heavy metal toxicity in a prospective cohort of patients referred for medical toxicology evaluation

INTRODUCTION

Provoked urine testing (PUT), involving chelating agent administration prior to measuring urine metal excretion levels, is used by some alternative health care practitioners to diagnose patients with heavy metal poisoning. Multiple medical societies have advised against this practice due to its presumed unreliability, expense, and lack of validation. However, no prospective study of the predictive value of PUT for heavy metal poisoning has been undertaken.

METHODS

This study utilized the Toxicology Consortium's prospective case registry to evaluate the reliability of PUT for diagnosing heavy metal poisoning. Inclusion criteria were toxicology clinic patients with PUT results who were subsequently evaluated by a board-certified medical toxicologist and had a determination made regarding whether their signs and symptoms were likely related or unrelated to toxicologic exposures. The primary outcome was the positive predictive value of PUT for heavy metal toxicity as diagnosed by the evaluating medical toxicologist. Patients presenting to participating toxicology clinics without PUT served as a comparison group.

RESULTS

74 of 106 cases presenting with PUT results met inclusion criteria and were analyzed. 15 cases were determined by the examining toxicologist to be likely related to a toxicologic exposure. Only three cases were found to be related to heavy metal exposure, giving a positive predictive value of 4.3%. 20.2% of patients with PUT were found to have signs or symptoms related to any toxicologic exposure, compared to 14.3% of clinic patients without PUT. Demographics of toxicology clinic patients with and without PUT results were not significantly different except for age.

DISCUSSION

Our results provide empiric support that PUT is an inaccurate predictor of a diagnosis of heavy metal poisoning by a board-certified medical toxicologist. Given the inability to properly interpret PUT results along with the increased cost burden and risk of false positives, PUT should not be performed.