England players allowed to take Viagra before World Cup clash against Mexico

England players have reportedly been allowed to take Viagra (Sildenafil), if needed, before their FIFA World Cup Round of 16 match against Mexico at Estadio Azteca. The drug could help manage altitude-related fatigue in Mexico City, which is 7,350 feet above sea level. Sildenafil is not banned by WADA and is permitted in competition for athletes.