Generic substitution of commonly used medications: Australia-wide experience, 2007-2008.
OBJECTIVE
To study the extent of brand substitution and switching in three commonly used classes of drugs available on the Pharmaceutical Benefits Scheme (PBS).


METHODS
Assessment of PBS claim records for a 1-year period from 1 August 2007 to 31 July 2008 for long-term concession cardholders drawn from a 10% random sample of the Australian population. The target drug classes were: statins (pravastatin, simvastatin), calcium channel blockers (CCBs) (amlodipine, felodipine, nifedipine), and selective serotonin reuptake inhibitor (SSRI) antidepressants (fluoxetine, fluvoxamine, paroxetine, sertraline).


METHODS
Proportion of patients who were non-switchers (single brand only) and multiple switchers (two or more brand switches).


RESULTS
We retrieved information relating to 935 334 prescriptions for 122 000 patients. Of those patients filling at least four prescriptions for a product, 41 174 patients received statins, 27 230 received CCBs and 21 342 received SSRIs. More than half the patients received only one brand during the study period: 57% for statins, 60% for CCBs, and 63% for SSRIs. Multiple switching was recorded for 24% of patients with statins, 19% with CCBs, and 21% with SSRIs, with smaller proportions receiving three or more brands: 14% for statins, 10% for CCBs, and 12% for SSRIs. Multiple switching was more common among younger patients for all drug classes (28% for those aged < 50 years v 18% for those aged >/= 80 years).


CONCLUSIONS
Generic substitution with multiple switches is occurring in a small proportion of patients being treated with statins, CCBs or SSRIs. The potential for patient confusion appears to be relatively small, but this may change with recent incentives included in pharmacy reimbursement arrangements.
Ortiz
Michael
M
Solvay Pharmaceuticals, Sydney, NSW, Australia.
Simons
Leon A
LA
Calcino
Gordon
G
D000368:Aged; D000369:Aged, 80 and over; D000928:Antidepressive Agents; D001315:Australia; D002121:Calcium Channel Blockers; D016568:Drugs, Generic; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008297:Male; D008875:Middle Aged; D055656:Prescriptions / Q000706:statistics & numerical data; D017367:Selective Serotonin Reuptake Inhibitors
D000928:Antidepressive Agents; D002121:Calcium Channel Blockers; D016568:Drugs, Generic; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D017367:Selective Serotonin Reuptake Inhibitors