As with any other type of medication, the manufacturers of the popular erectile dysfunction drug, Viagra, had to apply for a patent to sell the drug. Pfizer obtained the patent for Viagra back in 1992. It became the first oral treatment for male impotence to be sold in the United States. The patent for Viagra expired in 2012 in the US. This means that other companies can now manufacture the drug. Generic versions of the drug also appeared on the market in 2013 after Pfizer’s patent expired. Pfizer’s patent for Viagra expired in Brazil in 2010, and the patent has also recently expired in many other countries, including Denmark, the United Kingdom, Ireland, Italy and Spain.