A RECORD number of drug patents will expire over the next few years, which should heighten competition from generic drugs and force down prices. In 2009, $26 billion of sales were at risk from patent expiries. This will nearly double in 2011 according to EvaluatePharma, a consultancy. The price of any given drug falls by more than 85% within a year of a patent expiring in markets like America. About 13% of global drug sales are at risk from generic competition over the next two years.