Background and Importance It has been shown that the Medication-Regimen-Complexity-Index (MRCI) is a useful and reliable tool for calculating the complexity of the pharmacotherapeutic regimen (CPR). Furthermore, high MRCI is associated with lower adherence. However, MRCI in opioid-dependent patients (ODP) has not been studied.

Aim and Objectives Calculate the methadone-maintenance-programme (MMP) persistence and the MRCI score in a ODP cohort. Second, to analyse its relationship and association with other variables.

Material and Methods An observational study including adults with a confirmed diagnosis of opiate-dependence according to the DSM-5 in a MMP centre was carried out from November 2021 to April-2022.

To define MMP-persistence, a group was created with the researchers who defined five weighted items according to the importance agreed.

The variables collected were sex, age, social/work situation, comorbidities, substances consumption, methadone treatment (doses, frequency, duration, number of dropouts/interruptions since the MMP onset). MRCI score and MMP-persistence were calculated. They were collected and managed using REDCap. Statistical analysis was carried out using SPSS® Statistics (v.27).

The study was approved by the Ethics Committee.

Results 84 patients signed the informed consent. 79.8% were male (median age:51(46–56)). 25.4% had a job and 14.9% was homeless. 57.0% had any comorbidity. 62.5% had infectious disease and almost 40% mental health disorder.

Substances consumption was tobacco (81.4%), benzodiazepines (74.0%), cocaine (65.0%), alcohol (42.4%), heroin (33.9%) and cannabis (28.3%). 2.9% were intravenous-drug-users (IVDU). Median methadone dose was 60mg (40–80). 63.1% received maintenance doses. 38.1% received methadone for>10 years. None of the patients abandoned MMP at any time.

The median MRCI score was 13.5 (8.5–21.8) (maximum:40.5).

Regarding MMP-persistence, a patient was considered persistent with a score ≥90% according to our definition. We found 77.4% persistent patients.

No association was found between MRCI and MMP-persistence (p=0.74). However, the following variables had relationship: age (p=0.04), comorbidity (0.002) and patients receiving maintenance doses (p=0.024).

Regarding MRCI, we found association with age (p=0.04), homeless (p=0.002), comorbidity (p=0.0), HBV (p=0.003), mental health disorder (p=0.006), active heroin consumption (p=0.03) and IVDU(p=0.03).

Conclusion and Relevance A new MMP-persistence definition has been created. We identified age, comorbidities, and receiving methadone maintenance doses as successful predictors for MMP-persistence.

MRCI does not seem to be a useful tool to determine the MMP-persistence, probably because there are multiple factors that influence in addition to the CPR. It is necessary to continue searching for more precise selection and stratification tools for ODP to improve their persistence. However, it should not be an obstacle to implementing measures to optimise their pharmacotherapy.

Conflict of Interest No conflict of interest