BOTOX® (onabotulinumtoxinA) is a prescription medicine that is injected into muscles and indicated to prevent chronic headaches. Botox® has been approved for treating headaches that are present more than 15 days per month. It is used to prevent headaches in adults with chronic migraine, who have 15 or more days each month with headache lasting 4 or more hours each day, in people 18 or older.
Also referred to as Botulinum toxin, it is a neurotoxin produced by clostridium botulinum, the bacteria that thrive in conditions without oxygen (ie: anaerbic state), and may produce severe food poisoning called Botulism. This is the toxin that paralyzes nerves by blocking the release of a substance called acetylcholine which blocks nerve signals to muscles and prevents them from contracting thereby causing relaxation. The toxin is a poison only if ingested with a spoiled food.
However, for medicinal use, Botox® is injected directly into muscles rather than absorbed from the stomach. The injected dose is a fraction of that which causes botulism. No single case of Botulism related to Botox has ever been reported.
Botox® is well known for its use in treatment of wrinkles. It has approval for use in treating facial tics and spasms, dystonia and other forms of spasticity in cerebral palsy for example. Its tolerability and safety record for these uses are excellent.
The discovery of Botox® for treatment of migraine was quite by accident. Several patients who were using Botox® for injection of wrinkles and also happened to have migraine. They reported improvement in headaches following injection into their brow and forehead muscles.
The mechanism of action involved in the alleviation of headache is not entirely clear. One possibility is that Botox® may decrease muscle contraction that may act as a trigger to migraine. Another theory is that Botox® may act on the brain chemicals called neurotransmitters and mediators that trigger pain and migraine.
Careful trials studying migraine and chronic headache patients continue to examine the efficacy of Botox®. Several clinical trials including a large placebo controlled study, have been completed and demonstrated effectiveness of this therapy. Botox® is approved by FDA and Health Canada for treatment and prevention of chronic migraine. Health Canada approved Botox® for the treatment of chronic migraines in 2011. More studies exploring Botox® benefits in migraine and other types of headaches, are ongoing.
The average dose is 100-200 units. The onset of action is usually within the first 2-3 weeks of injection. However, patients may require a set of 2-3 injections before a maximum benefit is seen. Injections are spaced at 12 week intervals.