How did rofecoxib withdrawal influence overall non-steroidal anti-inflammatory drug (NSAIDs) and paracetamol prescribing in Australia?
Aim: The COX-2 inhibitors (COX-2), celecoxib, rofecoxib and meloxicam were introduced on the Australian market in 2000, 2001 and 2002, respectively. COX-2 introduction led to significant changes in drug consumption, probably due to marketing activity. The aim of this study was to measure COX-2 uptake and the impact on conventional NSAIDs and paracetamol prescribing. The effect of the voluntary rofecoxib withdrawal from the market (2004) on overall NSAID and paracetamol consumption was also evaluated.
Method: Dispensing data were downloaded from the Medicare Australia website for concession beneficiaries for paracetamol, non selective NSAIDs and COX-2 subsidized by the Pharmaceutical Benefit Scheme (PBS) over the period 1997-2005. Dispensing data were converted to WHO Anatomical Therapeutic Chemical (ATC)/Defined Daily Dose (DDD)(2005) and expressed as DDD/1000 concession beneficiaries/day. Drug Utilisation 90%(DU90%) was calculated.
Result: Non-selective NSAID usage decreased sharply with the introduction of COX-2. COX-2 increased the overall consumption of total NSAIDs in the first 3 years following their introduction (from 80 to 90 DDD/1000 beneficiaries/day). After rofecoxib withdrawal, the overall total NSAIDs use slightly declined (to about 75DDD/1000 beneficiaries/day). However, non-selective NSAIDs use increased in 2005. Celecoxib use slightly declined while there was an increase in meloxicam use in 2005 (to 20 DDD/1000 beneficiaries/day). Use of paracetamol was steady over the period 1997-2004 (around 40 DDD/1000 beneficiaries/day), with a small increase in 2005 after paracetamol sustained release was PBS listed. DU90% showed that paracetamol was the most used in 1997 and in 2005. However, COX-2 took over as the second and third most used drugs, displacing the non-selective NSAIDs.
Conclusion: The introduction of COX-2 at first increased the total NSAIDs use in concessionary beneficiaries in Australia. However, the total overall dispensing of NSAIDs in 2005 went back to similar value registered before COX-2 introduction. COX-2 replaced a big part of the non-selective NSAIDs dispensing and this is demonstrated by the changed composition of the products which make up the top 90% of the usage (DU90%).