Increase in hospitalisation-associated methadone intoxication in France following first COVID-19 lockdown

At the beginning of the COVID-19 pandemic, the French Addictovigilance Network drew attention to the need to facilitate access to methadone while ensuring its safe use, in order to avoid the occurrence of overdoses and deaths. The objectives of the study were to assess the impact of the lockdowns on the incidence of methadone-use-related hospitalisations (MUHs) and describe the characteristics of patients and hospitalisations.

An interrupted time series using the unobserved components model was performed to predict the monthly incidence of MUHs in 2020 on the basis of previous years' data and compared with MUHs observed. Data were presented with prediction intervals (PI_95%).

This retrospective study was conducted on patients hospitalised in France for methadone between 2014 and 2020, using the French national database hospital discharge database. Patients' characteristics and hospitalisations were described over four periods: before lockdown, first lockdown, after first lockdown, and second lockdown.

Compared to the predictions, a higher incidence of MUH was found during the first lockdown, especially in March 2020 (66 cases vs. 51.3; PI_95%: 34-65), and there was a large increase during the month following the end of the first lockdown (79 cases vs. 61; PI_95%: 46-75). Coconsumptions (alcohol, cannabis, cocaine) were more frequent during the first lockdown, whereas patients aged over 30 years were more concerned thereafter. The second lockdown did not present any particularity.

The first lockdown had a significant impact on the incidence of MUHs. These results confirm the data from the reinforced national monitoring during first lockdown published in 2020, where methadone was the primary substance involved in overdoses and deaths.