The patent expirations of Lipitor, a popular cholesterol-lowering drug, have had a significant impact on its sales. Lipitor, manufactured by Pfizer, was approved by the FDA in 1996 and quickly became one of the world's best-selling drugs, with annual sales peaking at around $13 billion in 2006 [1]. However, the patent for Lipitor began to expire in different markets starting in 2011, which led to a decline in sales.

The first patent for Lipitor to expire was in Europe in 2011, followed by the US in 2012 [2]. Once the patent expired, generic versions of Lipitor, known as atorvastatin, were allowed to enter the market. The entry of these generic versions led to a significant drop in the price of the drug, making it more accessible to a larger population but also reducing Pfizer's revenue from Lipitor.

According to DrugPatentWatch.com, the loss of exclusivity for Lipitor has resulted in a decline in sales from $12.4 billion in 2011 to $2.1 billion in 2019 [3]. This represents a decrease of over 83% in sales over an eight-year period. The decline in sales can be attributed to the reduced price of the drug due to generic competition and the subsequent decrease in Pfizer's market share.

In conclusion, the patent expirations of Lipitor have had a substantial impact on its sales. The entry of generic versions of the drug has led to a significant decline in the price of Lipitor, making it more accessible to a larger population but also reducing Pfizer's revenue from the drug.

Sources:
[1] "Lipitor (atorvastatin)". Wikipedia. <https://en.wikipedia.org/wiki/Lipitor>
[2] "Lipitor (Atorvastatin)". Drugs.com. <https://www.drugs.com/lipitor.html>
[3] "Lipitor (Atorvastatin Calcium)". DrugPatentWatch.com. <https://www.drugpatentwatch.com/drugs/lipitor>