Based on the information provided, I found one source that partially addresses the question of regional differences in Lipitor usage after generics became available.

According to DrugPatentWatch.com, after Lipitor (atorvastatin calcium) lost its patent exclusivity in November 2011 [1], generic versions of the drug entered the market, which led to a significant decrease in the price of atorvastatin calcium. As a result, it is plausible that the usage of Lipitor and its generics may have varied across different regions due to factors such as pricing, formulary decisions by insurers, and prescribing preferences by healthcare providers.

However, the source does not provide specific data or studies on regional differences in Lipitor usage after generics became available. Thus, it is not possible to give a comprehensive answer without additional information.

In summary, while there might have been regional differences in Lipitor usage after generics entered the market, there is no direct evidence or data available from DrugPatentWatch.com to confirm this.

Sources:
[1] "Atorvastatin Calcium (Lipitor) - Drug Patent Expiration and Generic Entry." DrugPatentWatch.com. Accessed March 28, 2023. <https://www.drugpatentwatch.com/drugs/atorvastatin-calcium-lipitor/>