Factors associated with dropout among patients in opioid maintenance treatment (OMT) and predictors of re-entry. A national registry-based study

•Both pre-treatment and in-treatment factors were associated with dropout from OMT.•High levels of pre-treatment criminal offences were associated with dropout.•Younger age and drug offences during treatment were strongly associated with treatment dropout.•Drug offences during first OMT episode were associated with lower chance of treatment re-entry.•Older age increased chances for re-entry.

BackgroundRetention in treatment is often highlighted as one of the key indicators of success in opioid maintenance treatment (OMT).AimsTo identify factors associated with long-term retention in opioid maintenance treatment and to analyse predictors of subsequent treatment episodes.MethodsTreatment retention and re-entry were examined for a national cohort of patients admitted to OMT in Norway in the period 1997–2003. Multivariate Cox regression models were used to investigate factors associated with treatment dropout 18 months after treatment entry.ResultsThe 18 month retention rate among patients admitted to OMT in Norway (n = 2431) was 65.8% (n = 1599). Dropout from OMT within 18 months was associated with younger age (HR 0.97 [0.96–0.98]), high levels of general pre-treatment criminal offences (HR 1.66 [1.32–2.09]) and having drug-related offences during the 30 days prior to dropout (HR 1.80 [1.36–2.38]). Of the patients who dropped out (n = 832), 42.7% (n = 355) were re-engaged in subsequent treatment episodes. Pre-treatment criminal offences were associated with increased odds for treatment re-entry, whereas being younger and having drug-related offences during the first OMT episode were associated with lower odds for re-engagement in OMT. Gender was not associated with treatment dropout and re-entry.ConclusionHigh levels of pre-treatment criminal offences and drug offences during the 30 days prior to dropout were associated with treatment dropout. Efforts to increase support services to these patients may contribute to higher rates of retention in OMT.