The introduction in 1990 of the Minimum Pricing Policy without allowing generic substitution had a relatively small impact on the selection of medicines within the Pharmaceutical Benefits Scheme. However the effect of generic substitution at the pharmacist level, which was introduced in December 1994, resulted in a marked increase in the percentage of eligible PBS items dispensed at benchmark. Case studies showed a larger premium resulted in a greater shift of patients from drugs with a brand premium to the benchmark alternative.

General practitioners are the major providers of treatment for depression in Australia. When writing prescriptions for tricyclic antidepressants GPs use doses lower than those recommended for major depression, however, most management in primary care is not for conditions regarded by the GP as major depression. A significant number of prescriptions for the newer antidepressants may not accord with the Pharmaceutical Benefits Scheme (PBS) restrictions for use.

Objective:To evaluate the impact of increasing the minimum re‐supply period for prescriptions on the Pharmaceutical Benefits Scheme (PBS) in November 1994. The intervention was designed to reduce the stockpiling of medicines used for chronic medical conditions under the PBS safety net. Methods:Interrupted times series regression analyses were performed on 114 months of PBS drug utilisation data from January 1991 to June 2000. These analyses assessed whether there had been a significant interaction between the onset of the intervention in November 1994 and the extreme levels of drug utilisation in the months of December (peak utilisation) and January (lowest utilisation) respectively. Both serial and 12‐month lag autocorrelations were controlled for. Results:The onset of the intervention was associated with a significant reduction in the December peak in drug utilisation; after the introduction of the policy there were 1,150,196 fewer prescriptions on average for that month (95%Cl 708,333–1,592,059). There was, however, no significant change in the low level of utilisation in January. The effect of the policy appears to be decreasing across successive post‐intervention years, though the odds of a prescription being dispensed in December remained significantly lower in 1999 compared to each of the pre‐intervention years (11% vs. 14%) Conclusion:Analysis of the impact of increasing the re‐supply period for PBS prescriptions showed that the magnitude of peak utilisation in December had been markedly reduced by the policy, though this effect appears to be decreasing over time. Continued monitoring and policy review is warranted in order to ensure that the initial effect of the intervention be maintained.

Aims To determine the frequency with which the selective serotonin re-uptake inhibitor (SSRI) antidepressants are used as add-on therapy to the tricyclic antidepressants (TCA) rather than as replacement therapy. Methods The data analysed were pro®les of prescription records by date of supply to the patient. From within the national administrative dispensing claims database, the subset eligible for social security entitlements was identi®ed as individuals by means of their coded permanent identi®cation numbers (PINs). Following the initial supply of an SSRI in January 1996, the subsequent 6 months dispensing of SSRI and TCA antidepressants to these individuals was examined. The main outcome measure was the proportion of individuals to whom SSRIs and TCAs were dispensed concurrently, as an indirect measure of coprescription. In instances where a patient was receiving prescriptions for SSRIs and TCAs that had been written by the one doctor only, the major specialty of the doctor was investigated.Results 55 271 PINs were dispensed 63 865 SSRI prescriptions in January 1996 which represented over half (52%) of the total community SSRI prescriptions dispensed in that month. The number of these patients meeting the criteria for coprescription of SSRIs and TCAs over the next 6 months was 2773 (5%). The coprescribing instances were highest in Queensland and the prescribers most frequently involved had psychiatry major specialty codes. Conclusions Among SSRI users there is a cohort of patients who, within the same time frame, are receiving supplies of a TCA, the nonselective drug that the SSRIs were designed to replace. This is indirect evidence of probable coprescription. Such combination use is of uncertain clinical and cost effectiveness, and carries additional risks. The SSRIs were included on the subsidy list in Australia on the basis of reasonable cost effectiveness as monotherapy compared with the TCAs. Our data imply that for some patients, antidepressant prescribing is inconsistent with the basis on which government subsidy was approved.

In 2000, only 40% of patients started on an antidepressant continued to be prescribed some antidepressant therapy 6-8 months later. Patients were more likely to continue on SSRIs as a class than on TCAs and the difference in continuation between these two classes occurred within the first 2 months of therapy. However, patients starting on an individual SSRI or TCA were equally likely to change to another antidepressant.