Botulinum toxin type A (Botox) has received a UK licence from the Medicines and Healthcare products Regulatory Agency (MHRA) for the prophylaxis of headache in adults with chronic migraine, defined as headaches on at least 15 days of the month, of which at least eight are with migraine.

The licence follows on from the findings of the PREEMPT (Phase III REsearch Evaluating Migraine Prophylaxis Therapy) programme, involving 1384 adults with chronic migraine (Headache 2010; e-pub ahead of print). Patients were randomised to receive either placebo or 155-195 units of Botulinum toxin type A administered as 31 injections into seven specific head and neck muscles, with up to eight lower dose injections into three of these muscles as a ‘follow the pain’ strategy. After 24 weeks, patients who had received two injection cycles of Botulinum toxin type A experienced an average of 8.2 fewer migraine days compared with 6.2 days fewer in the placeo group. Patients treated with Botulinum toxin type A also experienced significantly fewer headache days compared with placebo. Following an open-label phase of the trial, in which patients received a further three injection cycles over a 32-week period, nearly 70 per cent of patients treated with Botulinum toxin type A experienced at least a 50 per cent reduction in number of migraine days. Treatment was generally well tolerated with discontinuation rates of 3.8 per cent and 1.2 per cent in the botulinum toxin and placebo arms respectively.