Antidepressants: prevalence of duplicate therapy and avoidable drug interactions in Australian veterans

This study assessed the prevalence of duplicate antidepressant prescribing and avoidable potential antidepressant drug interactions in the Australian war veteran population.

The Department of Veterans' Affairs Pharmacy Claims database was interrogated, using specific criteria, to identify antidepressant duplication. In addition, potential drug interactions where safer alternative therapies were available were assessed. These included anticholinergic agents with tricyclic antidepressants and tramadol with antidepressants. Episodic tramadol dispensings with antidepressants were also assessed.

A total of 46,859 veterans had antidepressants regularly dispensed to them in the period 1 April-31 July 2005. Overall, 4037 potential interactions were identified in 3818 veterans (8.1%) to whom were dispensed antidepressants regularly. Antidepressant and tramadol co-prescribing was the most common potential interaction identified among 3.6% of veterans. Two or more interactions were identified in 212 veterans (0.5%). Analysis of episodic tramadol dispensings with antidepressants suggested a much higher prevalence of 7.7%.

The increasing use of antidepressants and the high level of potentially avoidable interactions detected in the present study, highlight the necessity of ongoing vigilance concerning the use of potentially inappropriate drug combinations, particularly in the elderly.