Data compiled on the top 100-selling drugs in the US in the first quarter of 2012 revealed mixed results for atorvastatin products, with generic sales of the cholesterol-lowerer up 90 per cent while Pfizer's Lipitor brand saw its sales cut in half.
Bristol-Myers Squibb's Plavix (clopidogrel) stole the top slot from Lipitor, with sales up almost 3 per cent to $1.62bn, while Pfizer's product slipped to 14th place with $841m in quarterly sales after losing patent protection in the US last year.
At the same time generic versions of atorvastatin rocketed ahead to reach 9th place with sales of $950m, even though only Watson and Ranbaxy have been authorised to sell generics in the first six months following Lipitor's patent expiry at the end of November 2011.
Plavix's reign at the top looks set to be short-lived, meanwhile, as the effect of recently launched generics will start to show an impact in the coming quarters, according to Drugs.com which compiled the survey.
Rounding out the top 5 drugs are AstraZeneca's gastrointestinal drug Nexium (esomeprazole), BMS' antipsychotic Abilify (aripiprazole), Merck & Co's Singulair (montelukast) for asthma and another antipsychotic, AZ's Seroquel (quetiapine).
All these drugs are at or near the end of period of exclusivity, with the patent on Seroquel already expired and generic versions of the drug expected in the third quarter of this year.
"The most recent sales data … highlights the continued stronghold of several branded medications," said Philip Thornton, Drugs.com's chief executive.
"However, with generic versions of Plavix and Lipitor now available and with a number of established brands moving to first-time generic status in the coming years, lower-cost medications will enable patients to have greater access to lifesaving treatments and save billions in healthcare dollars."
Aside from generic atorvastatin, other products rising through the ranks included AZ/Medimmune's respiratory syncytial virus (RSV) treatment Synagis (palivizumab), Merck/Johnson & Johnson's Remicade (infliximab) for arthritis and Crohn's disease and Eli Lilly's antidepressant Cymbalta (duloxetine).
Synagis rose 38 per cent to $110m in the quarter, while Remicade added 10 per cent to reach $82m and Cymbalta was up 8 per cent at $73m.
Among the big decliners are Eli Lilly's Zyprexa (olanzapine) - which closed the quarter with sales of $194m, down 49 per cent - and Forest Laboratories' antidepressant Lexapro (escitalopram) which fell 32 per cent to $491m.