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Botox (onabotulinumtoxin A)

Reviewed by: HU Medical Review Board | Last reviewed: May 2023 | Last updated: May 2023

Botox® (onabotulinumtoxin A) is an injectable preventive treatment. It is approved to treat people with chronic migraine. Chronic migraine is defined as headache occurring on 15 or more days per month for more than 3 months, where at least 8 of those headache days have migraine features.1,2

What are the ingredients in Botox?

The active ingredient in Botox is onabotulinumtoxinA.1

How does Botox work for migraine?

Botox works by binding to receptors on nerves and muscle fibers. This blocks the release of specific brain chemicals, including acetylcholine. This, in turn, blocks muscle activity. It is not completely known how Botox reduces headache pain and stiffness. A potential reason might be that Botox blocks nerves that send pain messages to the brain and relaxes muscles so they are less sensitive to pain.1

Botox is injected into the muscles of the neck and face by a doctor. There are 31 injection sites. The recommended treatment schedule is every 12 weeks. Your doctor will talk to you about what is right for your specific case.1

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What are the possible side effects?

The most common side effects of Botox include:1

  • Neck pain
  • Headache

Botox has a boxed warning, the strictest warning from the US Food and Drug Administration (FDA). It has this warning because the effects of Botox and all botulinum toxin products may spread from the area of injection to produce symptoms such as:1

  • Trouble swallowing
  • Muscle weakness
  • Double vision
  • Drooping eyelids
  • Blurry vision
  • Slurred speech
  • Breathing problems
  • Trouble moving the eyes

These symptoms may occur hours to weeks after injection. Get emergency help if you have swallowing or breathing problems since they can be life-threatening.1

These are not all the possible side effects of Botox. Talk to your doctor about what to expect when receiving Botox. You also should call your doctor if you have any changes that concern you when receiving Botox.

Other things to know

You should not receive Botox injections if you:1

  • Are allergic to any of the ingredients in Botox
  • Had an allergic reaction to any other botulinum toxin product such as Myobloc®, Dysport®, or Xeomin®.
  • Have a skin infection at the planned injection site.
  • Are being treated for urinary incontinence and have a urinary tract infection (UTI).
  • Are being treated for urinary incontinence and you cannot empty your bladder on your own

Before starting treatment with Botox, tell your doctor if you have:1

  • A disease that affects your muscles and nerves, such as ALS/Lou Gehrig's disease, myasthenia gravis, or Lambert-Eaton syndrome
  • Had side effects from any botulinum toxin product in the past
  • Current or previous breathing problems, such as asthma or emphysema
  • Current or previous swallowing problems
  • Current or previous bleeding problems
  • Plans to have surgery
  • Previous surgery on your face
  • Weakness of your forehead muscles, such as trouble raising your eyebrows
  • Drooping eyelids
  • Any other change in the way your face normally looks
  • Symptoms of a urinary tract infection (UTI) and are being treated for urinary incontinence
  • Problems emptying your bladder on your own and are being treated for urinary incontinence

There is not enough data to know if Botox is safe to receive while pregnant or breastfeeding. Before receiving Botox, tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding. They can help you decide if Botox is right for you.1

Using Botox with certain other medicines may cause serious side effects. Before receiving Botox, tell your doctor if you:1

  • Have received any other botulinum toxin product in the last 4 months
  • Have received injections of botulinum toxin, such as Myobloc, Dysport, or Xeomin in the past
  • Have recently received an antibiotic by injection
  • Take muscle relaxants
  • Take an allergy or cold medicine
  • Take a sleep medicine
  • Take anti-platelets (aspirin-like products) or blood thinners

Before beginning treatment for migraine, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of Botox.