Allergan has received a boost with the news that regulators in the USA have given the green light to the firm's wrinkle smoother Botox as a treatment for the prevention of chronic migraine in adults.

The US Food and Drug Administration has approved Botox (onabotulinumtoxin A) for the prophylactic treatment of headaches in adults with chronic migraine, characterised by severe headaches on 15 or more days per month, lasting four hours or longer.Allergan noted  that Botox is the first prophylactic to be given the thumbs-up by the FDA "specifically for this debilitated patient population".

When injected in the head and neck, Botox is expected to produce results lasting up to three months, the company said. The approval was based on the PREEMPT programme, the largest ever in chronic migraine, which consisted of two trials involving 1,384 adults from 122 study sites in North America and Europe.

In both PREEMPT studies, patients treated with Botox experienced a significantly greater decrease in the frequency of headache days from baseline compared to those on placebo at the week 24 primary endpoint (7.8 and 9.2 fewer days versus 6.4 and 6.9 days). Also at week 24, Botox patients reported a total cumulative reduction in headache hours by 107 and 134 hours, respectively, compared to 70 and 95 hours with placebo.

Botox, best-known for its cosmetic use (but also other medical conditions such as excessive sweating) has been used 'off-label' for migraine for many years, and analysts believe that getting the new approval could add around $1 billion a year to Allergan's coffers. The US thumbs-up comes four months after the UK became the first country in the world to approve Botox as a preventive treatment for chronic migraine.