Generics Despite a decline in sales owing to the generic entry of most triptans, the launch of emerging acute treatments and the uptake of Allergan's Botox for prevention of chronic migraine will drive the market for migraine therapies to increase from $3.3 billion in 2011 to $5.8 billion in 2021 in the leading markets of the USA, France, Germany, Italy, Spain, the UK and Japan, according to health care advisory firm Decision Resources. 18 November 2012