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

BACKGROUND Retention in treatment is often highlighted as one of the key indicators of success in opioid maintenance treatment (OMT). AIMS To identify factors associated with long-term retention in opioid maintenance treatment and to analyse predictors of subsequent treatment episodes. METHODS Treatment 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 18months after treatment entry. RESULTS The 18month retention rate among patients admitted to OMT in Norway (n=2431) was 65.8% (n=1599). Dropout from OMT within 18months 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 30days 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. CONCLUSION High levels of pre-treatment criminal offences and drug offences during the 30days 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.