Benzodiazepine prescription for patients in treatment for drug use disorders: a nationwide cohort study in Denmark, 2000–2010

BACKGROUND: Benzodiazepines are frequently prescribed to patients with drug use disorders. However, it has previously been difficult to distinguish whether this frequent prescribing was due to underlying psychiatric disorders or inappropriate prescribing. In a nationwide cohort study, we investigated the prescribing of benzodiazepines to patients with drug use disorders in connection with treatment admission. METHODS: Benzodiazepine prescriptions to patients (N = 33203) aged 18 to 67 years admitting for outpatient treatment for drug use disorders in Denmark, 2000 to 2010, were studied by using linked data from nationwide health registries. Factors associated with increasing amounts of benzodiazepine use within the first year after admission were assessed by multinomial logistic regression. Proportions of very long-term benzodiazepine prescription were calculated. RESULTS: During the first year after admission to treatment, 26.2 % of patients were prescribed benzodiazepines. Of these, 35.5 % were prescribed benzodiazepines at dose levels that might indicate inappropriate use (>365 Defined Daily Dose per year), and 34.6 % were prescribed more than one type of benzodiazepines. Diazepam was the most commonly prescribed type. Among patients with opioid use, 43.2 % were prescribed benzodiazepines which were three times higher than for patients with cannabis (12.2 %) or central stimulating drugs (13.8 %) as their primary drug use. Admitting to treatment for a drug use disorder did not increase the specialized psychiatric treatment coverage of this patient group, disregarding use of prescribed benzodiazepines. 29.5 % were new users of prescribed benzodiazepines, and of these, 27.5 % continued into very long-term use (≥4 years after admission) during the study period. CONCLUSIONS: Benzodiazepines were commonly prescribed to patients admitting to treatment for drug use disorders, and included prescription of multiple and non-optimal types, high doses, and very long-term prescriptions. These findings point towards inappropriate prescribing of benzodiazepines in many cases more than treatment for psychiatric disorders.