Lipitor (atorvastatin) was the top-selling prescription medication in the United States in 2010, earning its manufacturer, Pfizer, more than $7 billion in total revenue. The overall market for prescription lipid-lowering drugs continues to grow; this drug class had greater prescription volume than any other class in 2010, with statins dominating the market.1 Lipitor's patent expired in June 2011, and the first generic version entered the market on November 30.
The financially constrained U.S. health care system is seeking ways to safely and effectively cut costs. Since generic drugs are cheaper than brand-name formulations and are generally considered bioequivalent to them, health plans commonly promote generic substitution in efforts to blunt the growth in prescription-drug spending. Over the next few years, as several other blockbuster drugs lose their patents, generic products will become increasingly available.
To explore the possible economic impact of the availability of generic atorvastatin, we examined past trends in statin use to project potential future cost savings. The similar scenario of the market entry of generic simvastatin when the patent for Zocor (Merck) expired in 2006 provided a historical example to guide our projections, including information on timing of generic-product use, changes in the average prices of generic and brand-name products, and the extent to which patients switched to other drugs within the statin class. We also considered the effect that the aging of the population would have on the demand for statins. We believe our estimates of cost savings with generic atorvastatin are conservative, given the historical simvastatin patterns. When generic simvastatin entered the market, Zocor had immense competition from Lipitor, a high-potency statin, whereas Lipitor has no competitor that offers an advantage over it. Crestor (rosuvastatin) (AstraZeneca), a new higher-potency statin, has not been shown to be superior to Lipitor in reducing risk and so is unlikely to command a large share of the market.
In the United States, Lipitor, Crestor, and generic simvastatin accounted for 77% of the statin market in 2009. Lipitor's market share dropped from 44% in 2006 to 26% in 2009, when simvastatin dominated the statin market, with a market share of 41%.
The current market shares of Lipitor and simvastatin are estimated at 21% and 51%, respectively. According to NEJM assumptions, generic atorvastatin will dominate the statin market as a result of patients' switching to it from simvastatin and from Crestor, and it will have an estimated market share of 44% by 3 years after market entry, Generic atorvastatin's lower price makes it less costly than Crestor and competitively priced with generic simvastatin, and atorvastatin doesn't pose the risk of myopathy that high-dose simvastatin does.
If Pfizer's agreements extending Lipitor's monopoly truly result in the provision of a brand-name drug at a generic price with savings realized by patients, pharmacy-benefits management and insurance companies and employers, the only short-term losers might appear to be the competing generics firms. But without the possibility of gaining some atorvastatin market share, generics companies may forgo competition, preventing the typically sharp long-term decline in generic prices and resulting in a lost opportunity for reducing systemwide spending. Whatever happens, Lipitor's generic transition should be watched closely, since Pfizer's strategies may set a new precedent for the other blockbuster drugs on the verge of losing their patents.
Source:[NEJM]
by
Akshaya Srikanth, Pharm.D Internee
Hyderabad, India
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