Ayerst Labs

Pharmaceutical company founded in Montreal in 1925 as Ayerst, McKenna and Harrison and later run as Ayerst Laboratories within American Home Products, best known for the conjugated oestrogens sold as Premarin and for early work on vitamin D and reserpine. Merged with Wyeth to form Wyeth-Ayerst Laboratories and then simply Wyeth, whose business passed to Pfizer in 2009, and made prescription medicines with its own research laboratories and manufacturing in Canada and the United States.