Abstract for presentation at National Medicines Symposium 2006

Switching between brand name and generic medicines: the example of simvastatin

  • Ms Lisa Kalisch, Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute, University of South Australia, Australia
  • Associate Professor Elizabeth Roughead, Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute, University of South Australia, Australia
  • Professor Andrew Gilbert, Quality Use of Medicines and Pharmacy Research Centre, Sansom Institute, University of South Australia, Australia

    • Since introduction of the brand substitution policy to the Pharmaceutical Benefits Scheme (PBS) in 1994, use of generic medicines and the number of generics available has increased. In 2005 when over 400 generics were available, 56% of PBS prescriptions were dispensed at the patient co-payment price, compared to 17% in 1994. There is potential for patient confusion and harm when brands and generics are switched, particularly if switching is common. A small Australian study found that 56% of patients do not understand the difference between brand and generic names of medicines. Currently, the extent of switching between brand and generic medicines is unknown. This study aimed to identify simvastatin switching rates and associated factors. The first simvastatin generic was PBS listed in November 2004. Switching rates were compared pre and post generic simvastatin availability. A switch was identified if different brands or generics were dispensed consecutively. Analyses were conducted using Repatriation Pharmaceutical Benefits Scheme prescription claims data. Prior to generic availability when two non-substitutable brands were available, there was one switch per 279 prescriptions dispensed. This was most commonly associated with the use of a different prescription (87% of switches), rather than a repeat of the same prescription. The switching rate on individual prescriptions was one switch per 1,773 dispensings. Following introduction of the first generic the overall switching rate increased to one switch per 14 dispensings. Of these switches, 24% coincided with dispensing at a different pharmacy to the previous and 70% were associated with the use of a different prescription. When individual prescriptions were followed the switching rate was lower, with one switch per 38 dispensings. In 21% of these cases, the switch coincided with a change in pharmacy at which the medicine was dispensed. The introduction of a simvastatin generic appears to have increased switching. Further work will identify switching rates after August 2005 when ten simvastatin brands and generics were available.

    Conference Organiser - ICMS Pty Ltd