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Botox: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Jan 5, 2023.

1. How it works

  • Botox is a brand name for a specific type of botulinum toxin, called onabotulinumtoxinA that may be used to treat a wide range of conditions, such as migraines, strabismus, and reducing frown-lines (Botox Cosmetic).
  • Botulinum toxins are neurotoxins produced by a type of bacteria called Clostridium botulinum and there are eight different types of botulinum toxins produced by C. botulinum; A, B, C1, C2, D, E, F, and G. Botox is a type A botulinum toxin and it works by blocking the release of acetylcholine, one of the most significant neurotransmitters in our body. Acetylcholine activates muscles, so blocking it causes muscle relaxation and paralysis. Botox injections place botulinum toxin directly into a specific muscle. There it has a direct effect on acetylcholine in nerve synapses, blocking signals that would normally cause the muscle to contract.
  • Botox belongs to the class of medicines known as skeletal muscle relaxants.

2. Upsides

  • Botox may be used to treat:
    • Chronic migraines that occur more than 15 days per month and last more than 4 hours each time. The recommended retreatment schedule is every 12 weeks
    • Focal dystonias - involuntary muscle contractions in a specific body area (such as in the neck) in people over the age of 16
    • Hemifacial spasm - involuntary twitching of muscles on one side of the face
    • Hyperhidrosis - excessive sweating
    • Hypersalivation - increased saliva
    • Overactive bladder symptoms such as incontinence when other medications are ineffective or not tolerated
    • Blepharospasm and strabismus (eye misalignment [one eye faces a different way to the other]) associated with dystonia in people aged 12 years and older
    • Neurogenic detrusor overactivity (an overactive bladder disorder caused by a dysfunction in the nerves that supply the bladder) in pediatric patients 5 years of age and older who do not respond to, or are intolerant of, anticholinergic medication.
  • Botox Cosmetic is FDA approved for moderate to severe glabellar lines (forehead furrows), canthal lines (crows feet), and forehead lines.
  • The only difference between Botox and Botox Cosmetic is that they are used to treat different areas of the body, and their concentrations (Botox is available in 100 units or 200 units, and Botox Cosmetic is available in 50 units and 100 units). They both work in the same way.
  • Botox and Botox Cosmetic are purified forms of botulinum toxin that when injected in tiny, controlled doses is very safe and effective at relaxing excessive muscle contraction, even though ingestion of food contaminated with C. botulinum causes botulism - an often fatal, paralytic-type illness.
  • Has been in use since the 1970s when it was first approved to treat strabismus - an abnormal alignment of the eyes.
  • Type A botulinum toxins (found in Botox, Botox Cosmetic, and some other brands) are the most potent and long-lasting forms of botulinum toxin.
  • Botox Cosmetic temporarily smoothes out lines, creases, and wrinkles on the face, chin, neck, and chest.
  • Several other types of spastic movement disorders and some other long-term conditions not effectively treated by other types of medical treatment also have reported success with botulinum toxins. The medical uses for botulinum toxins are likely to expand in the future.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Facial paresis, droopy eyelids, neck pain, muscle stiffness or weakness or pain, or injection site reactions are side effects that may be experienced, but these are uncommon. In rare instances, Botox has spread beyond the injection site and caused serious, potentially life-threatening, such as difficulty swallowing or breathing, overall muscle weakness, blurred vision, drooping eyelids, and voice changes. Children being treated for spasticity (muscle spasms) and people with certain underlying conditions are more at risk. Effects may occur hours to weeks after administration.
  • Tell your patient to call emergency services if they experience any problems swallowing, speaking, or breathing soon after botulinum toxin administration or other symptoms indicating toxin spread, such as muscle weakness, vision changes, eyelid drooping, or loss of bladder control.
  • Retrobulbar hemorrhages sufficient to compromise retinal circulation have occurred following the administration of Botox for strabismus. Decompress the orbit if necessary.
  • Do not use in people who are hypersensitive to any botulinum toxin product or any components of the vial. There should be no infection at the proposed injection site.
  • Must be administered by a licensed provider and reconstituted exactly as directed by the manufacturer.
  • Botox is NOT interchangeable with the other 3 types of botulinum toxin type A preparations available in the U.S., which are abobotulinumtoxinA [Dysport], incobotulinumtoxinA [Xeomin], and prabotulinumtoxinA-xvfs (Jeuveau), and the one botulinum toxin type B preparation (rimabotulinumtoxinB [Myobloc]). This is because each manufacturer uses assay methods specific to their company, so even though dosages may be quoted in similar-sounding units, potency can vary several fold between the different products. Care needs to be taken that the correct dosage stated is used for that particular product and the approved indications for the different products also vary.
  • Fraudulent Botox products may exist. Always check the translucent silver Allergan seal is intact on the Botox carton labeling. or the vial label contains a holographic film with the name Allergan with rainbow-colored horizontal lines on it, and there is a U.S. license number 1145 on the vial label and carton labeling.
  • When used to treat bladder dysfunction, patients should not have a post-void residual (PVR) urine volume of more than 200mL if they are not self-catheterizing, nor a urinary tract infection (UTI) at the time of the appointment. Prophylactic antibiotics, except aminoglycosides (eg gentamicin), should be administered 1-3 days pre-treatment, on the treatment day, and 1-3 days post-treatment to reduce the likelihood of procedure-related UTI. Patients should discontinue anti-platelet therapy at least 3 days before the injection procedure. Patients on anticoagulant therapy need to be managed appropriately to decrease the risk of bleeding. For those with an overactive bladder, intravesical instillation of diluted local anesthetic with or without sedation may be used before injection.
  • Monitor those with compromised respiratory status closely when they are being treated with Botox for spasticity. The change in forced vital capacity (FVC) (more than 15-20%) was greater with Botox than with placebo.
  • Vigorous blinking from Botox injection of the orbicularis muscle can lead to an epithelial defect and corneal ulceration. Consider protective drops, ointment, soft contact lenses, closure of the eye by patching or other means.
  • Because Botox contains albumin, a derivative of human blood there is a theoretical risk for transmission of Creutzfeldt-Jakob disease (CJD) and other viral diseases, but no cases of transmission have ever been identified.
  • There are no studies using Botox in pregnant women. In animal studies, Botox administration resulted in adverse effects on fetal growth (decreased fetal weight and skeletal ossification). There are no data on the presence of Botox in human milk or adverse effects on the developing infant. Consider the benefits of Botox versus the risks, and advise against breastfeeding unless the risk is justified.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

  • Botox is approved to treat many conditions, such as chronic migraine, involuntary muscle contractions or twitching, excessive sweating, increased saliva, and overactive bladder to name a few. Botox Cosmetic is approved to temporarily improve the appearance of forehead furrows and lines and crows feet. Botox must be injected by a licensed provider and the effects generally wear off within 2 to 4 months. Side effects are rare, but strenuous activity should be avoided immediately after each appointment.

5. Tips

  • Botox should only ever be injected by a licensed provider. Do NOT attempt to inject this at home yourself as serious and potentially life-threatening side effects may occur.
  • Licensed providers use a thin needle to inject Botox into the targeted muscle or gland. Dosages vary depending on the size of the muscle (larger muscles require higher dosages), who is being injected (some females may require lower dosages), and the presence of pre-existing muscle weakness. Electromyography (using a needle electrode to test muscle movement) may be used to guide injection in delicate areas.
  • Rest and avoid strenuous activity after each appointment to minimize toxins dislodging and traveling due to increased blood circulation. In addition, laser/IPL treatments, facials, and facial massage should be avoided for one to two weeks after injections or as directed by your licensed provider.
  • Call emergency services if you experience any problems swallowing, speaking, or breathing soon after botulinum toxin administration or other symptoms indicating toxin spread, such as muscle weakness, vision changes, eyelid drooping, or loss of bladder control.
  • Tell your doctor if you are pregnant, intending to become pregnant, or breastfeeding before being administered Botox because it may not be suitable for you.

6. Response and effectiveness

  • Only Type A and Type B botulinum toxins are commercially available.
  • Effects are usually seen within 24-72 hours, peak around ten days, and can last 2 to 4 months until new nerve terminals sprout and form new synaptic contacts.
  • Resistance to Botox may develop. This is because botulinum toxin type A found in Botox is a type of protein. As with any protein, antibodies can potentially develop with repeated exposure, because the body views it as an antigen, activating the immune response. Once formed, these antibodies block the effects of the botulinum toxin (Botox), neutralizing its action. Most case reports concern onabotulinumtoxinA (Botox, Botox Cosmetic), the first botulinum toxin to be marketed. In 1997, the original formulation was changed to reduce the protein load per dose, and since then treatment failure rates have dropped; however, experts estimate 0.3 to 6% of people are still at risk of antibody development. The risk is greatest when dosages of more than 200 units per session are used, and reinjection occurs within one month. Experts are unsure if neutralizing antibodies resolve over time or if injections of botulinum toxin type B products are useful in patients with neutralizing antibodies to type A.

7. Interactions

Medicines that interact with Botox may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with Botox. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Botox interacts with just over 110 different medications. Common medications that may interact with Botox include:

  • amikacin
  • aminoglycosides such as gentamicin
  • anticholinergics such as benztropine
  • antipsychotics, such as chlorpromazine or clozapine
  • atracurium
  • atropine
  • azatadine
  • baclofen
  • belladonna
  • glycopyrrolate
  • hydroxyzine
  • kanamycin
  • neomycin
  • oxybutynin
  • other botulinum toxin preparations, such as Dysport or Xeomin
  • other muscle relaxants, such as carisoprodol, dantrolene, or orphenadrine
  • pimozide
  • sedating antihistamines such as brompheniramine, diphenhydramine, or doxylamine
  • scopolamine
  • streptomycin
  • tobramycin
  • tricyclic antidepressants, such as amitriptyline, clomipramine, desipramine, or doxepin
  • vecuronium.

Note that this list is not all-inclusive and includes only common medications that may interact with Botox. You should refer to the prescribing information for Botox for a complete list of interactions.


Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Botox only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2023 Revision date: January 5, 2023.