A real-world systematic review of the forensic implications regarding serum testing in compliance monitoring

The purpose of this systematic review is to study the correlation between the daily dose of oral opioids/ intrathecal opioids and resultant serum levels in relation to established blood toxicity levels used forensically. Between April 2018 and October 2022, serum opioid test results of 1,583 patients were analyzed from our clinical private practice. A broad literature search was conducted with the key words, “Blood concentrations of opioids”, which returned 7,993 results in PubMed. A smaller search was performed in PubMed with the key words, “cytochromes that metabolize opioids”, which yielded 1,387 results. Additionally, a confidential Excel spreadsheet was created by the American Institute of Toxicology Laboratories in Denton, Texas and was provided to our clinical practice. Simple linear regression was performed in Excel to determine the correlation coefficient, R-squared value, for each prescribed opioid. The result was an unexpected weak correlation between the daily opioid dose and serum concentration. The most surprising finding is an “overlap” between measured serum levels of all opioid groups with the toxic range in Baselt. In conclusion, the endpoint of opioid prescribing should focus on maximizing activities of daily living and achievement of functional goals utilizing serum level analysis, tempered by Centers of Disease Control guidelines. Serum testing can suppress physician vulnerability created by patients dying, (who were taking prescribed opioids). Future research analyzing the concentration of oral opioids in the cerebrospinal fluid in comparison to the concentration of opioids in the cerebrospinal fluid in the same patient after intrathecal opioid monotherapy would be interesting.