Evaluation of thallium levels in opioid substance users: A case–control study

Aims: Drug abuse is one of the major problems threatening human health. The presence of heavy metals (e.g., lead and thallium) in illicit drugs has raised concerns. This study was designed and performed to indicate the status of thallium in the urine of opioid users with symptoms similar to thallotoxicosis and compare them with the control group. Materials and Methods: This case–control study was conducted in Kashan with the participation of 200 people (including 100 people in the opioid user group and 100 people in the control group). Then, electrothermal atomic absorption spectrometry was used to determine the concentrations of urinary thallium. Findings: In the opioid group, the median (interquartile range) urinary thallium concentrations was 72/29 ± 49/33 μg/l, whereas in the control group, it was 5/57 ± 3/015 μg/l. There was a significant difference in the concentrations of urinary thallium between the opioid group and the control group. Furthermore, the prevalence of thallotoxicosis-related clinical symptoms was significantly higher in the opioid group with high urinary thallium concentrations compared with the control group (weakness, fatigue, paresthesia, ataxia, vertigo, memory deficits, tremor, aggressiveness, tinnitus, sweating, rashes, dry skin, constipation, nausea, vomiting, abdominal pain, and diarrhea). Conclusions: The results of the present study indicated that the levels of urinary thallium in patients using illicit opioids are significantly higher, which can be due to contamination of drugs with thallium.