Patentová historie přípravku Viagra®
Viagra® (sildenafil citrate) is one of the most sold drugs for erectile dysfunction treatment. The patents of Pfizer Inc. relating to sildenafil expired in Europe and Canada in 2013. At present, a generic sildenafil can be sold all over the world, except for the USA. The district court in Norfolk, VA confirmed that US patent 6,469,012 is valid and enforceable. Moreover, the additional six months of the exclusivity of Viagra® has been granted due to the clinical trial of sildenafil to be used for treatment of paediatric pulmonary arterial hypertension. Therefore the protection of Viagra® for the largest market, USA, remains till April 2020.