Refining the excretion factors of methadone and codeine for wastewater analysis - Combining data from pharmacokinetic and wastewater studies.

Analysing drug residues in wastewater (wastewater analysis) to monitor the consumption of those drugs in the population has become a complementary method to epidemiological surveys. In this method, the excretion factor of a drug (or the percentage of drug metabolites excreted through urine) is a critical parameter for the back-estimation of the consumption of a drug. However, this parameter is usually derived from a small database of human pharmacokinetic studies. This is true for methadone and codeine, the two most commonly used opioids and also common substances of abuse. Therefore, we aimed to refine the current excretion factors used for estimating methadone and codeine by analysing published data from the literature on the excretion of methadone, its main metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), and codeine. Our review included both human drug pharmacokinetic studies and wastewater analysis studies. We found that while the commonly used excretion factor of methadone (~27.5%) was relatively accurate, the excretion factor of EDDP, a better biomarker for methadone consumption in sewer epidemiology, should be twice that of methadone (i.e. 55%) instead of the current equal or half values. For codeine, the excretion factor should be ~30% instead of 63.5% or 10% as previously used in wastewater analysis studies. Data from wastewater analysis studies could be used in this way to refine the excretion factors of the drugs of interest.

Challenges and opportunities in using wastewater analysis to measure drug use in a small prison facility.

INTRODUCTION AND AIMS: Wastewater analysis (WWA) is intended to be a direct and objective method of measuring substance use in large urban populations. It has also been used to measure prison substance use in two previous studies. The application of WWA in this context has raised questions as to how best it might be used to measure illicit drug use in prisons, and whether it can also be used to measure prescription misuse. We applied WWA to a small regional prison to measure the use of 12 licit and illicit substances. We attempted to measure the non-medical use of methadone and buprenorphine and to compare our findings with the results of the prison's mandatory drug testing (MDT). DESIGN AND METHODS: Representative daily composite samples were collected for two periods of 12 consecutive days in May to July 2013 and analysed for 18 drug metabolites. Prescription data and MDT results were obtained from the prison and compared with the substance use estimates calculated from WWA data. RESULTS: Daily use of methamphetamine, methadone, buprenorphine and codeine was detected, while sporadic detection of ketamine and methylone was also observed. Overall buprenorphine misuse appeared to be greater than methadone misuse. DISCUSSION AND CONCLUSIONS: Compared with MDT, WWA provides a more comprehensive picture of prison substance use. WWA also has the potential to measure the misuse of medically prescribed substances. However, a great deal of care must be exercised in quantifying the usage of any substance in small populations, such as in prisons.

Monitoring substance use in prisons: Assessing the potential value of wastewater analysis.

Prison substance use is a major concern for prison authorities and the wider community. Australia has responded to this problem by implementing the National Corrections Drug Strategy. Across Australia, the true extent of prison substance use cannot be determined. As a result, the effectiveness of the interventions employed as part of this strategy cannot be properly assessed. This has important implications for the allocation of corrective services resources and future policy development. This article explores the benefits and limitations, as well as the ethical and practical issues in using wastewater analysis (WWA) to measure levels of substance use in prisons. It reports results from the first application of WWA to an Australian prison, which supports the use of WWA in this context. Given the increasing concern for prescription misuse in prisons, we also highlight the novel use of WWA to measure the extent of prescription misuse by prisoners. The article concludes that as a result of its objectivity, sensitivity and cost-effectiveness, the use of WWA in prisons warrants further consideration in Australia.