Botox (onabotulinumtoxinA) is a brand-name injection prescribed to help prevent headaches in adults with chronic migraine. This article covers topics such as side effects, dosage, and how Botox works.

Botox is a biologic that belongs to a drug class called neurotoxins. The drug is not available in a biosimilar version. A biosimilar is a medication that is similar to a biologic drug (known as the reference drug). Biosimilars are considered to be as safe and effective as the reference drug.

Boxed warning: Spread of toxin effects

Botox has a boxed warning for the spread of toxin effects. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Before receiving Botox” section.

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Using Botox to help prevent migraine headaches may cause mild or serious side effects. The following lists include some of Botox’s main side effects that may occur while using Botox for migraine headache prevention.

To learn about other possible side effects of the drug, talk with your doctor or pharmacist. You can also refer to Botox’s prescribing information.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medications safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect while receiving Botox and want to tell the FDA about it, visit MedWatch or call 800-332-1088.

Mild side effects

Botox injections for migraine can cause mild side effects. These side effects may be temporary, lasting for a few days or weeks. But if they last for a longer time, bother you, or become severe, it’s important to talk with your doctor or pharmacist.

Mild side effects of Botox injections for migraine can include:

You may be wondering whether Botox can cause long-term effects. Drooping eyelids caused by Botox injections usually go away on their own within a few weeks. But if you notice any side effects from Botox injections that don’t go away on their own, be sure to talk with your doctor. They can recommend treatments and adjust your medication plan as needed.

Serious side effects

Botox injections for migraine can cause serious side effects, though this is rare. Call your doctor right away if you develop serious side effects while using Botox. If the side effects seem life threatening or you think you’re having a medical emergency, call 911 or your local emergency number immediately.

Serious side effects of Botox injections for migraine can include:

  • allergic reaction
  • spread of toxin effects, which could cause life threatening problems with swallowing or breathing

Botox has a boxed warning for the spread of toxin effects. A boxed warning is the most serious warning from the FDA. For more information, see the “Before receiving Botox” section.

Botox is approved by the FDA to help prevent headaches in adults with chronic migraine.

Dosage

The recommended dose of Botox for migraine is 155 total units divided into 31 injections.

A healthcare professional will administer these injections in seven specific muscle areas in your head and neck. Each muscle area has several sites where the healthcare professional will inject 0.1 milliliters (mL) of Botox. In terms of units, 0.1 mL is about 5 units. The healthcare professional will administer the 155 units across 31 sites in your head and neck muscles.

You’ll likely receive the injections every 12 weeks.

Note: In addition to preventing headaches in adults with chronic migraine, Botox has other FDA-approved uses. Botox’s dosage differs for its other uses. For more information, talk with your doctor.

How Botox is given

Botox comes as a powder in a single-use vial. The drug is mixed into a liquid solution. For migraine headache prevention, you’ll receive the medication as intramuscular injections from a healthcare professional.

Injection sites

Because intramuscular injections are given directly into a muscle, you may be wondering about the injection sites for migraine headaches. The Botox injection sites for this use are:

  • between your shoulder and neck on your right and left sides
  • at the back of your neck, by the base of your skull on your right and left sides
  • the back of your head, behind each ear
  • the middle of your forehead, above each eye
  • the lower part of your forehead, right above your nose
  • the lower part of your forehead, near the inside edge of each eyebrow
  • behind each temple, above the ear

How often it’s given

To prevent headaches in adults with chronic migraine, you’ll typically receive Botox injections every 12 weeks. However, your doctor will recommend a dosing schedule that’s right for you.

Two clinical trials have demonstrated the effectiveness of Botox injections in preventing headaches in adults with chronic migraine.

In these trials, adults with chronic migraine received injections of Botox or a placebo (treatment with no active drug ingredient). They had two sets of injections, which they received 3 months apart.

Researchers compared the number of headache days people had at the start of the trial with the number they had after 6 months of treatment. The results showed that people who received Botox averaged fewer headache days than people who received a placebo.

How much Botox costs depends on several factors. These can include your prescribed treatment regimen, the insurance plan you have, and your location. The price also depends on the cost of the appointment to receive doses of Botox from your healthcare professional.

To learn more about Botox and cost, ask your doctor or pharmacist for more information.

Here are some frequently asked questions about using Botox for migraine.

Can using Botox for migraine also help with wrinkles? Does it change your face’s appearance?

Botox only relieves the specific nerves in the muscle groups it’s injected into. So receiving Botox injections to help prevent headaches is unlikely to affect wrinkles or change your face’s appearance.

However, it’s possible that Botox might cause your forehead to look slightly smoother. It’s also possible for some side effects of Botox to change how your face looks, such as drooping eyelids. Side effects are typically temporary.

A different medication called Botox Cosmetic can help smooth out wrinkles. Botox Cosmetic contains the same active ingredient (onabotulinumtoxinA) as Botox, but it’s given in lower doses. Botox Cosmetic is given in different injection sites for wrinkles than those used to help prevent headaches.

Note that the manufacturer warns against using Botox interchangeably with other botulinum toxin products. Also, Botox should not be used for conditions that haven’t been approved by the FDA. Doing so can result in serious side effects.

This means Botox should not be used for treating wrinkles. Likewise, Botox Cosmetic should not be used to help prevent migraine headaches. Also, other botulinum toxin products should only be used for conditions the FDA has approved them for.

If you have questions about using Botox to help prevent headaches or Botox Cosmetic for wrinkles, talk with your doctor.

What can I expect when I receive Botox injections for migraine?

Botox injections for migraine are generally safe, but they may cause some side effects. To learn more, see the “Botox side effects” and “Receiving Botox injections” sections, and talk with your doctor.

Botox is approved by the FDA to help prevent headaches in adults with chronic migraine.

The way Botox works

Botox is a type of drug called a neurotoxin, and it stops nerves from functioning.

Your nerves usually communicate with other areas of your body using acetylcholine, a neurotransmitter. (Neurotransmitters are chemical messengers.)

Botox works by stopping nerves from releasing acetylcholine. This means that your nerves can’t tell muscles to spasm (tighten). When used to help prevent migraine headaches, Botox blocks nerve signals that cause pain.

Some adults who receive Botox injections to help prevent migraine headaches experience improvements in their condition within 2 to 4 weeks. But keep in mind that it can take two sets of injections and a full 6 months before you feel the maximum effects from Botox.

Migraine explained

Migraine is a condition that can cause several symptoms, including severe headaches that can be pulsing and debilitating. These tend to occur on one side of your head and can last from a few hours to a few days. Migraine is considered chronic if you have headaches that last for at least 4 hours on 15 or more days each month.

Botox isn’t used for episodic migraine (which causes symptoms that occur on 14 or fewer days per month). The drug’s safety and effectiveness for this type of migraine isn’t known.

Symptoms of migraine

Migraine symptoms tend to occur in stages.

Before a migraine headache: It’s possible to have symptoms that begin hours or days before a headache. Some people may experience a sensory aura that involves vision changes, such as blind spots or light flashes. Other people have tingling or buzzing sensations or difficulty speaking.

During a migraine headache: This stage might involve a mild-to-severe pulsing, throbbing headache. This can last from a few hours to a few days. You may also experience nausea and vomiting. In addition, you may have increased sensitivity to light and sound.

After a migraine headache: Some people call this the “migraine hangover.” Tiredness and irritability are common and may last for up to 2 days. During this time, you may have difficulty performing regular activities due to lingering pain. Increased sensitivity to light or sound is also possible. In addition, you may have head pain that worsens with physical activity or straining.

Botox and children

Botox isn’t approved to help prevent headaches in children with chronic migraine.

Before you receive Botox injections to help prevent migraine headaches, there’s some important information to note. The drug may not be a safe option for you if you have certain medical conditions or other factors that affect your health. These are described in the following text.

Boxed warning: Spread of toxin effects

This drug has a boxed warning. This is the most serious warning from the FDA. A boxed warning alerts doctors and patients about drug effects that may be dangerous.

After Botox is injected, the drug may sometimes spread to other parts of the body. This can lead to a serious condition called botulism, which may cause symptoms such as:

  • muscle weakness
  • lack of energy
  • double vision
  • drooping eyelids
  • difficulty speaking
  • hoarse voice
  • difficulty swallowing
  • difficulty breathing
  • loss of bladder control

It’s possible for botulism to occur hours, days, or weeks after receiving Botox. If you experience any of the listed symptoms after having a Botox injection, you should talk with your doctor.

In rare instances, the difficulty swallowing or breathing that botulism may cause can be life threatening. If you already have difficulty swallowing or breathing, you may have an increased risk of these problems. Call your doctor immediately if you have difficulty swallowing or breathing after receiving a Botox injection. If you think your symptoms are life threatening, call 911 or your local emergency number.

Other warnings

In addition to a boxed warning, Botox has other warnings.

If any of the following medical conditions or other health factors apply to you, talk with your doctor before using Botox:

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.