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Botox Side Effects

Generic name: onabotulinumtoxinA

Medically reviewed by Philip Thornton, DipPharm. Last updated on Dec 25, 2023.

Note: This document provides detailed information about Botox Side Effects associated with onabotulinumtoxinA. Some dosage forms listed on this page may not apply specifically to the brand name Botox.

Applies to onabotulinumtoxinA: powder for solution.

Important warnings This medicine can cause some serious health issues

Injection route (powder for solution)

Distant spread of toxin effects - The effects of onabotulinumtoxinA and all botulinum toxin products may spread from the area of injection to produce symptoms consistent with botulinum toxin effects.

These symptoms have been reported hours to weeks after injection.

Swallowing and breathing difficulties can be life threatening and there have been reports of death.

The risk of symptoms is probably greatest in children treated for spasticity but symptoms can also occur in adults, particularly in those patients who have an underlying condition that would predispose them to these symptoms.

Precautions

It is very important that your doctor check your or your child's progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to receive it. Blood and urine tests may be needed to check for unwanted effects.

Serious muscle reactions have occurred within hours to weeks after receiving this medicine. If you start to have muscle weakness, loss of bladder control, or trouble with swallowing, talking, or breathing, call your doctor right away. In some patients, these problems could be life-threatening and may require an immediate treatment in a hospital or clinic.

This medicine may make your muscles weak and cause vision problems (eg, bleeding inside the eye). Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

This medicine may reduce blinking of the eye which can lead to an increased risk of eye problems (eg, corneal exposure and ulcers). Tell your doctor right away if you have a reduced blinking of the eye.

This medicine may cause serious allergic reactions, including anaphylaxis, which can be life-threatening and requires immediate medical attention. Call your doctor right away if you have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth while you are receiving this medicine.

After you have received this medicine and your vision or muscle spasms are better, you may find that you are a lot more active than you were before. You should slowly increase your activities to allow time for your body to get stronger. Also, before you start an exercise program, check with your doctor.

This medicine may increase your chances of having bronchitis or upper respiratory tract infections when given for upper limb spasticity. Tell your doctor right away if you have trouble breathing, sneezing, sore throat, coughing, or a fever.

This medicine may cause a condition called autonomic dysreflexia in patients with nervous system disorders (eg, spinal cord injury). It can be a life-threatening condition and requires immediate medical attention. Call your doctor right away if you have headache, increased sweating, slow heartbeat, warmth or redness in your face, neck, or arm, or have problems in urinating while using this medicine.

This medicine is made from donated human blood. Some human blood products have transmitted viruses to people who have received them, although the risk is low. Human donors and donated blood are both tested for viruses to keep the transmission risk low. Talk with your doctor about this risk if you are concerned.

Check with your doctor right away if you have difficulty urinating or a burning sensation while urinating after receiving this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of Botox

Along with its needed effects, onabotulinumtoxinA (the active ingredient contained in Botox) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking onabotulinumtoxinA:

More common side effects

  • difficulty with swallowing

Rare side effects

  • difficulty with breathing or speaking
  • muscle weakness

More common—for blepharospasm

More common—for upper limb spasticity

More common—for urinary incontinence caused by an overactive bladder

Less common—for blepharospasm

Less common—for forehead lines

Less common—for glabellar lines

Less common—for lateral canthal lines

Less common—for upper limb spasticity

Other side effects of Botox

Some side effects of onabotulinumtoxinA may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common—for blepharospasm

More common—for cervical dystonia

More common—for chronic migraine

More common—for forehead lines

More common—for hyperhidrosis

More common—for strabismus

More common—for upper limb spasticity

Less common—for blepharospasm

Less common—for chronic migraine

Less common—for forehead lines

Less common—for lower limb spasticity

Less common—for strabismus

For healthcare professionals

Applies to onabotulinumtoxinA: injectable powder for injection.

General adverse events

The more commonly reported adverse reactions have included localized pain and headache, otherwise reactions vary based on condition being treated. Local weakness of the injected muscle(s) represents the expected pharmacological action while weakness of nearby muscle may also occur due to spread of toxin.[Ref]

Gastrointestinal

Deaths as a complication of severe dysphagia have been reported with botulinum toxin. In cervical dystonia patients, dysphagia was reported in 19% of patients. Most dysphagia was reported as mild or moderate, however, dyspnea accompanied dysphagia in about 20% of these cases.[Ref]

Respiratory

Patients in the upper limb spasticity trials who had stable, reduced respiratory function at baseline experienced a greater event rate change in forced vital capacity (15% or greater or 20% or greater decline) compared with placebo at weeks 1, 6, and 12. These differences from placebo were not statistically significant, but noticeable. Among patients with restrictive lung disease of neuromuscular aetiology and detrusor overactivity associated with a neurologic condition, the event rate of decreased forced vital capacity (FVC) of 15% or 20% or more was also greater in treated patients compared with placebo. Bronchitis has been reported more frequently in patients treated for upper limb spasticity (3% vs 1%) compared with placebo. In patients with reduced lung function treated for upper limb spasticity, upper respiratory tract infections were reported more frequently in treated patients compared with placebo (up to 11% vs 6%). In patients treated for lower limb spasticity, upper respiratory tract infections were reported more frequently compared with placebo (2% vs 1%). In pediatric patients treated for upper limb spasticity, upper respiratory tract infections were reported more frequently compared with placebo (17% [6 units/kg]; 10% [3 Units/kg]; 9% [placebo]).[Ref]

Nervous system

Genitourinary

In trials in patients with overactive bladder (OAB), the more commonly reported adverse reactions within the first 12 weeks after intradetrusor injection were urinary tract infection (UTI; 18%), dysuria (9%), urinary retention (6%), bacteriuria (4%) and residual urine volume (3%). A higher incidence of UTI was observed in patients with diabetes than those without (31% vs 26%). The incidence of UTI increased in patients who experienced a maximum post-void residual (PVR) urine volume over 200 mL following injection compared to those whose PVR urine volume was 200 mL or less (44% vs 23%).

Among patients with detrusor overactivity associated with a neurologic condition, urinary tract infection and urinary retention occurred in 24% and 17%, respectively.

Musculoskeletal

Cardiovascular

Botulinum Toxin:

Local

Ocular

Hypersensitivity

A fatal case of anaphylaxis has been reported; in this case, lidocaine was used as the diluent and therefore, the causal agent cannot be determined.

Other

Dermatologic

Immunologic

Hematologic

Psychiatric

See also:

References

1. "Product Information. Botox (onabotulinumtoxinA)." Allergan Inc

2. (2022) "Product Information. Botox Cosmetic (onabotulinumtoxinA)." Allergan Inc

Frequently asked questions

Further information

Botox side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.