Examining the adequacy of quantities available for subsidized antidepressant prescriptions in Australia

In Australia the Pharmaceutical Benefits Scheme (PBS), a national drug insu rance plan, aims to provide around a month's therapy for medication used in chronic conditions. However, there are marked differences among the most c ommonly used antidepressants in the number of days supply represented by th e PBS maximum quantity after adjustment for the defined daily dose (DDD). T he DDD is the assumed adult daily dose for a drug and is a WHO drug utiliza tion standard. Whereas the selective serotonin re-uptake inhibitors (SSRIs) and moclobemide largely provide around a month's supply at the DDD, most t ricyclic antidepressant (TCA) items provide considerably less than this. A patient tracking study was conducted to determine the average length of t ime between prescription re-supplies for a number of tricyclic antidepressa nts and newer antidepressants as a means of measuring the efficiency of PBS supply for the different classes of antidepressant. The number of days bet ween dispensings was similar for patients no matter whether they were takin g TCAs, SSRIs or moclobemide, although for the older antidepressants presum ably at a much lower prescribed daily dose than the DDD. Care needs to be taken when adjusting usage with the DDD/1000/day unit of m easurement in cases where thr: DDD does not reflect the prescribed daily do se (PDD). Copyright (C) 1999 John Wiley & Sons, Ltd.