http://insulinnation.com/treatment/why-walmart-insulins-arent-the-answer-to-high-insulin-prices/

There are three insulins available at Walmart for the price of $25 – NPH, Regular, and 70/30 (a mix of the two). NPH was first approved by the FDA in 1950, Regular was approved in 1982, 70/30 in 1989. That means NPH has been around for 66 years, Regular for 33 years, 70/30 for 27 years.