Cimetidine was first marketed in the United Kingdom in 1976, and in the . in August 1977; therefore, it took 12 years from initiation of the H 2 receptor antagonist program to commercialization. By 1979, Tagamet was being sold in more than 100 countries and became the top-selling prescription product in the ., Canada, and several other countries. In November 1997, the American Chemical Society and the Royal Society of Chemistry in the . jointly recognized the work as a milestone in drug discovery by designating it an International Historic Chemical Landmark during a ceremony at SmithKline Beecham's New Frontiers Science Park research facilities in Harlow, England.