One factor that influenced Lipitor use is patent protection [1]. Lipitor, a statin medication used to lower cholesterol, was first approved by the FDA in 1997 and was initially marketed by the pharmaceutical company Pfizer. According to DrugPatentWatch.com, the original patent for Lipitor expired in 2011 [2]. However, follow-on patents, known as "second-wave" or "second-generation" patents, extended the patent protection for the drug's active ingredient until 2017 in some countries.
The patent protection led to a significant increase in Lipitor's sales, making it one of the highest-grossing prescription drugs of all time [3]. Once the patent expired, generic versions of Lipitor became available, leading to a decrease in sales for the original formulation.
Sources:
[1] DrugPatentWatch.com (www.drugpatentwatch.com)
[2] DrugPatentWatch.com (www.drugpatentwatch.com) - Lipitor patent expiration date
[3] Pfizer's Lipitor (www.pfizer.com) - historical sales data