Botox (onabotulinumtoxin A) is an injectable muscle paralytic drug used for migraine prevention. It had been approved as a medical treatment for severe muscle rigidity and for cosmetic use to smooth out wrinkles before it was approved by the U.S. Food and Drug Administration (FDA) in 2010 for the prevention of chronic migraines.
When used for migraine prevention, Botox injections are scheduled about every three months because the effects are not permanent. With time, most people who experience a decrease in migraine frequency and severity with Botox are able to have less frequent injections.
Botox is derived from a toxin produced by the bacteria Clostridium botulinum. The toxin temporarily blocks the release of chemicals involved in nerve signaling, decreasing muscle activity.
Accidentally ingesting the toxin through spoiled food can cause an illness known as botulism, which produces dangerous muscle paralysis throughout the body. This can be fatal because it may interfere with breathing and heart function long before the effects of the toxin wear off.
But when used properly for therapeutic or cosmetic purposes, botulinum toxin is isolated and placed into a liquid solution for a carefully targeted injection that only paralyzes the injected muscles, greatly reducing the concerns associated with systemic effects.
The muscle paralysis produced by Botox treatments lasts for a few months, so repeated injections may be necessary.
How Botox Helps Migraines
The understanding of how Botox may help migraines is still developing. However, the way Botox works as a migraine preventive has nothing to do with its effect on muscle. Instead, it’s believed to work at nociceptive (pain) recepetors via a mechanism inhibiting release of inflammatory mediators and preventing central sensitization.
Some evidence suggests that botulinum toxin may also have an impact on neurotransmitter release in the brain and on the brain's pain receptors.
Research on Prevention
For those who suffer from chronic migraine, which is defined as 15 or more days of headache per month for at least three consecutive months, studies suggest that Botox has a small to moderate positive effect when it comes to preventing migraines. There have been many small trials examining the effect of Botox injections on migraine frequency and severity.
For example, a study in Spain included 69 participants who had chronic migraines. Each received an average of two botulinum toxin injections. The study authors reported that participants experienced a significant reduction in their pain intensity and number of headache days over the 16-month duration of the study.
A larger review included data from 28 trials, including a total of 4190 participants. The researchers only included randomized double-blind controlled trials, a standard that is considered the most reliable and unbiased method of testing a medication. Participants received various brands of botulinum toxin injections.
The researchers who investigated this large compilation of studies reported that participants who received botulinum toxin injections experienced an average reduction of three headache days per month, while participants who received a placebo injection experienced an average of one less headache day per month, suggesting that botulinum toxin has an impact.
So far, the science and evidence regarding the effectiveness of Botox injections for chronic migraine prevention is promising, but not overwhelmingly so.
Injections: What to Expect
Botox injection for chronic migraine prevention should take no longer than five to 15 minutes. During the procedure, several sites around the head and neck are injected. While you may feel a slight burning or pinprick sensation with each injection, the discomfort is short-lived, and most people tolerate it well.
When you undergo a Botox treatment, your healthcare provider will likely place at least 31 injections into seven key muscles of the head and neck. These seven areas of muscles include:
- Corrugator: Located at the inner end of each eyebrow
- Procerus: Located between the eyebrows
- Frontalis: Located at the front of the head (forehead)
- Temporalis: Located on each side of the skull (the muscle used for chewing)
- Occipitalis: Located near the back of the skull
- Cervical paraspinal muscle group: Located at the top and back of the neck surrounding the spine
- Trapezius: Located at the upper back and back of the neck
Additional muscles may be injected depending on the location of your typical headaches.
The injections generally need to be repeated every 12 weeks. It usually takes more than one Botox treatment and can take up to six months to see a therapeutic benefit when Botox is used for migraine prevention.
Side Effects and Warnings
Botox can produce side effects. It should always be injected by a trained professional. If your anatomy is asymmetric, or if the dose you receive is not exactly equal on your left and right sides, you may develop a slightly lopsided facial appearance for a few months until the medication starts to wear off.
Other side effects that can occur include:
- Muscle weakness
- Blepharoptosis (eye drooping)
- Skin tightness
- Paresthesia (unusual skin sensations)
- Neck stiffness
- Neck pain or soreness
Technically, Botox is a toxin, not an infection. But some people develop an immunity to the toxin, making it ineffective. You can develop this reaction whether you are getting Botox for muscle disease, cosmetic reasons, or migraine prevention.
There are also some rare, but potentially serious and life-threatening adverse events that can occur after a Botox injection. These effects may occur as a result of very high injection doses, unusual sensitivity to the medication, or to spreading of the medication to other areas beyond the injected muscle.
These adverse events may occur hours to weeks after injection and require immediate medical attention.
Get emergency medical attention if you experience any of the following:
- Problems swallowing, speaking, or breathing
- Loss of muscle strength
- Double vision, blurry vision, inability to open one or both eyelids
- A hoarse voice, slurred speech
- Loss of bladder control
Keep in mind that Botox can be quite expensive. Many insurance companies require extensive documentation proving that other preventive migraine therapies have been ineffective before covering the cost of Botox. Some payers do not cover it all, regardless of the situation.
A Word From Verywell
Treatment of chronic migrainesfocuses on a combination of behavioral interventions, such as trigger avoidance, and pharmacological treatments. Injections, such as Botox, muscle relaxants, and local anesthetics, as well as interventional surgical procedures, are growing in popularity.
Botox appears to provide some benefit in preventing chronic migraines. One of the advantages is that you can use Botox even if you continue to take medications for migraine treatment or prevention because they do not interact with each other.
Prescription Medications for Migraine Prevention
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Colleen Doherty, MD
Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.
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