Campaigners welcomed the move which will see patients receive injections of the muscle-paralysing toxin on their face, head and neck every 12 weeks to prevent the onset of migraines and reduce pain.
It is thought that around 3,764 people in Scotland will be eligible for the treatment annually, at a cost of £1,380 per patient.
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However, the Scottish Medicines Consortium expects that the actual uptake will be around 83 patients in the first year, adding an estimated £99,000 to the NHS drugs bill, and rising to 232 patients and a cost of £278,000 after five years. Additional costs for specialist nurses to administer the injections are estimated at £119,000 in the first year rising to £335,000.
The decision to approve Botox for migraine treatment brings Scotland into line with the rest of the UK, and comes after two previous rejections by the SMC. Migraine patients in England and Wales have had access to the treatment since 2012.
Dr Alok Tyagi, a consultant neurologist at the Queen Elizabeth University Hospital in Glasgow said: “We welcome this decision. The routine availability of this treatment will lead to a significantly improved quality of life for patients reducing their unnecessary suffering, use of NHS resources and days missed from work.”
Hannah Verghese, advocacy, policy and campaigns manager at The Migraine Trust, added: “Increasing the number of treatment options for people with this highly debilitating and disabling condition offers the prospect of reduced pain, reduced social isolation and a greater quality of life, particularly for those who find the current available treatment options ineffective.
"Although this decision is a positive one the Scottish Parliament and NHS Scotland must still commit to do more to ensure that the hundreds of thousands of people suffering from headache and migraine in Scotland receive the best possible care throughout the health system.”
Chronic migraines are defined as having at least 15 headaches per month lasting four or more hours - at least eight of which are migraine attacks.
Migraines are thought to be caused by changes in the chemicals of the brain, in particular serotonin. As well as an intense throbbing pain, symptoms can include visual distortions such as zigzag or flashing patterns, nausea, vomiting or increased sensitivity to bright light, noise or smell.
While Botox is still better known as a cosmetic "wrinkle-freezing" treatment popularised by celebrities, doctors are increasingly discovering alternative uses for it - including a potential therapy for depression, abnormal heartbeat and severe neck spasms.
It is unclear why it appears to counteract migraine, but it has been suggested that Botox may reduce blood pressure within the brain by relaxing muscles around the head or that it could reduce the nerves’ ability to send pain signals during a migraine.
Scottish migraine sufferer Elaine Bell, 50, has suffered from the debilitating attacks all her life, as did her mother, grandmother and great-grandmother.
She said: "As a young child at school the only medication available to me was paracetamol, which I used to swallow by the bucket load but it had no effect on my migraine at all. I can recall my grandfather when I was very young applying cold compresses to my head and using his hands to tightly hold my head in order to give me some relief."
Ms Bell said Botox, which she has been funding privately for two years, has "significantly" reduced the severity and frequency of her migraines.
She said: "After decades of missed family events, opportunities, work, education and social functions I am finally experiencing an overall improvement in the quality of my life and that of my family.
"I have received two treatments since January 2015 but my private healthcare provision restricts the number of treatments to two and I have been increasingly worried that without Botox my life would once again recede."
Professor Jonathan Fox, chairman of the SMC, said: “For those suffering with chronic migraine for which other treatments have not been effective, botulinum toxin type A (Botox) fulfils an unmet need."