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A botulinum toxin shot sold as Botox, FDA approved for migraine, eye-muscle spasms and facial lines; its effects can spread.
The botulinum toxin type A product approved in the United States as Botox and Botox Cosmetic, with potency Units specific to this preparation and a boxed warning for distant spread of toxin effect.
The label directs storage of unopened vials in a refrigerator at 2 to 8 °C.
Side effects and warnings
Boxed warning: the toxin's effects can spread from the injection spot, hours to weeks later. Trouble swallowing or breathing can be life threatening. Deaths have been reported.
Spread can cause weakness, double or blurry vision, droopy eyelids, trouble speaking and loss of bladder control. The risk of swallowing and breathing problems is highest in children treated for muscle stiffness (spasticity).
Common side effects depend on the use. For migraine: neck pain and headache. For facial lines: droopy eyelids or brows. For bladder uses: urine infections, pain when passing urine, and trouble emptying the bladder, which may need a tube (catheter).
A summary of the sources on this page, not medical advice.
Also called: botulinum toxin type A, BoNT/A, Oculinum
Regulatory (US)
FDA approval:approved
503A compounding:not-applicable Not a compounding question (approved finished product or supply).
Oculinum (original name of Botox) — Strabismus and blepharospasm associated with dystonia in patients 12 years and older (US, 1989)
Botox Cosmetic — Temporary improvement in the appearance of moderate to severe glabellar lines in adults (US, 2002)
Botox — Prophylaxis of headaches in adults with chronic migraine (US, 2010)
Botox Cosmetic — Temporary improvement in the appearance of moderate to severe lateral canthal lines in adults (US, 2013)
Botox Cosmetic — Temporary improvement in the appearance of moderate to severe forehead lines in adults (US, 2017)
Botox Cosmetic — Temporary improvement in the appearance of moderate to severe platysma bands in adults (US, 2024)
Molecule
MW: 150 kDa dichain neurotoxin (~100 kDa heavy chain and ~50 kDa light chain), formulated as a purified neurotoxin type A complex
Origin
Discovered by: Alan B. Scott, Smith-Kettlewell Eye Research Institute
Year: 1989
Developer: Allergan, now part of AbbVie
What it is
OnabotulinumtoxinA is the generic name of a botulinum toxin type A product. In the United States it is sold as Botox. For cosmetic uses it is sold as Botox Cosmetic. It is a protein made by a germ called Clostridium botulinum. The protein is cleaned up and supplied as a powder. A clinician mixes the powder with salt water (saline) before the injection.
When it is injected into a muscle, it blocks the signal that tells the muscle to tighten. The muscle relaxes for a few months. Then the nerve endings grow new connections, and the muscle works again. This is how both the medical and cosmetic uses work. Medical uses include neck muscle spasms (dystonia) and an overactive bladder. In cosmetic use, relaxing a frown muscle softens the line above it.
The strength of the product is measured in Units. These Units apply to this product only. They cannot be swapped for the Units of any other botulinum toxin product.
OnabotulinumtoxinA is a purified botulinum neurotoxin type A produced by fermentation of Clostridium botulinum type A (Hall strain) and supplied as a sterile vacuum-dried neurotoxin complex with human albumin and sodium chloride. The core neurotoxin is a 150 kDa dichain protein: a ~100 kDa heavy chain and a ~50 kDa light chain joined by a disulfide bond.
The heavy chain binds SV2 and polysialogangliosides on presynaptic cholinergic terminals and mediates endocytosis and translocation of the light chain into the cytosol. The light chain is a zinc-dependent endopeptidase that cleaves SNAP-25, a SNARE protein required for fusion of acetylcholine vesicles with the presynaptic membrane. Transmission is blocked until new terminals sprout and SNAP-25 is replenished, which is why clinical effect is temporary and the label sets minimum retreatment intervals.
Potency is assigned by a manufacturer-specific assay. The label states explicitly that Units of BOTOX are not interchangeable with those of other botulinum toxin products.
Who made it and when
Alan B. Scott was an eye doctor. In the 1970s he began injecting cleaned-up botulinum toxin into eye muscles. He wanted a way to fix a squint without surgery. He called the product Oculinum, which roughly means “eye aligner”. The FDA licensed Oculinum in December 1989. It was approved for a squint (strabismus). It was also approved for blepharospasm, where the eyelids close on their own.
Allergan had been handing out the product. It bought the product in 1991 and renamed it Botox. Over the next three decades, the list of approved uses grew in two ways. Nerve and bladder uses were added under the Botox name. Facial line uses were added under Botox Cosmetic, starting with frown lines in 2002. Allergan is now part of AbbVie.
Scott’s work at the Smith-Kettlewell Eye Research Institute, published from 1980 onward, established intramuscular botulinum toxin type A as a reversible chemodenervation agent. Oculinum was licensed under BLA 103000 on 29 December 1989 for strabismus and blepharospasm associated with dystonia in patients 12 years and older. Allergan acquired Oculinum Inc. in 1991 and rebranded the product BOTOX.
Subsequent US approvals under the same BLA include cervical dystonia, severe primary axillary hyperhidrosis, upper and lower limb spasticity in adults and in paediatric patients, urinary incontinence due to detrusor overactivity associated with a neurologic condition, overactive bladder, paediatric neurogenic detrusor overactivity from 5 years of age, and prophylaxis of headaches in chronic migraine (15 October 2010). The cosmetic franchise adds glabellar lines (2002), lateral canthal lines (2013), forehead lines (2017) and platysma bands (October 2024).
What the data say
There is an unusually large amount of evidence for this injection. That is because each use needed its own trials. For long-term (chronic) migraine, there were two matching trials called PREEMPT 1 and PREEMPT 2. Together they included nearly 1,400 adults. People got injections in a set pattern of 31 spots. The total was at least 155 Units every 12 weeks. Other people got a dummy treatment (placebo). When the results were combined, the Botox groups had fewer headache days than placebo. This result is why Botox is approved for migraine.
The newest approval is for the up-and-down neck bands called platysma bands. It is based on two trials of roughly 400 people each, reported in 2024. These trials also used a placebo. Across all uses, most side effects happen near the injection spot. But the label has a boxed warning, the FDA’s strongest warning. This is because the toxin’s effects can show up away from the injection spot.
PREEMPT 1 (NCT00156910, n=679) and PREEMPT 2 (NCT00168428, n=705) used identical 24-week double-blind phases followed by a 32-week open-label phase, with a fixed-site fixed-dose paradigm of 155 to 195 Units per cycle. PREEMPT 1 missed its original primary endpoint of headache episodes but met headache-day endpoints; PREEMPT 2 met its primary endpoint of change in headache days, and the pooled analysis, which supported registration, reported a significant between-group difference in headache days at week 24 with a tolerability profile dominated by neck pain and muscular weakness.
The platysma programme comprised two multicentre placebo-controlled phase 3 studies, M21-309 (NCT04949399, n=408) and M21-310 (NCT04994535, n=426), with a co-primary of investigator- and participant-assessed improvement. Participants were randomised by baseline severity to a single treatment of 26, 31 or 36 Units, or placebo, with the primary assessment at day 14. Immunogenicity remains a recognised limitation across indications: neutralising antibody formation can reduce response with repeated high-dose exposure.
Regulatory picture
In the United States, only two FDA-approved products contain onabotulinumtoxinA. They are Botox and Botox Cosmetic, both made by Allergan, an AbbVie company. Nothing else with this ingredient is approved here. Some botulinum toxin products are only licensed in other countries. When these are brought in or sold online for injection, they are not FDA approved.
The FDA has taken action on this many times. In April 2024 it warned the public that fake Botox had reached patients in several states. The CDC reported harmful reactions in 19 people in nine states. In November 2025 the FDA announced 18 warning letters. They went to websites selling unapproved and wrongly labelled botulinum toxin products. Pharmacies cannot make their own copies (compounding) of this kind of licensed product.
OnabotulinumtoxinA is licensed under BLA 103000. As a biological product it is not eligible for the 503A bulk drug substances route, and no legal pathway exists for a pharmacy to compound a copy, so the compounding field is recorded here as not applicable rather than restricted.
Unapproved botulinum toxin products entering the US market are unapproved new drugs under section 505 and misbranded under section 502 of the FD&C Act. FDA’s April 2024 alert described counterfeit material bearing an outer carton naming the active ingredient as “Botulinum Toxin Type A” instead of “OnabotulinumtoxinA” and strengths not produced by the manufacturer. The November 2025 action targeted 18 websites offering unapproved and misbranded botulinum toxin products in the United States. Clinical harm reported to CDC in 2024 was consistent with systemic botulinum toxin effect, and four patients received botulism antitoxin.
Dose
Doses reported in trials and studies
How dosing worked in the studies
The PREEMPT 1 and 2 trials are finished. They included 679 and 705 adults with long-term (chronic) migraine. They compared onabotulinumtoxinA with a dummy treatment (placebo). People got at least 155 Units as 31 injections into muscle. The injections went into set spots across seven head and neck areas. Some got up to 195 Units across 39 injections. This was repeated every 12 weeks. The M21-309 and M21-310 trials are also finished. They included 408 and 426 adults with prominent neck bands (platysma prominence). People were assigned by chance to one treatment into muscle, or to salt water (saline). The dose was 26, 31 or 36 Units, based on how severe the bands were at the start. Other studies that assigned people by chance tested 25 U or 75 U into head muscles against an inactive injection. One tested 50 U per armpit, injected into the skin, against placebo. Another tested 20, 40, 60 and 80 U in the frown-line area.
Label dosing (FDA-approved products)
The BOTOX label recommends 100 Units injected into the detrusor for overactive bladder (which it calls the maximum recommended dose), 200 Units per treatment into the detrusor for adult detrusor overactivity associated with a neurologic condition, 155 Units given intramuscularly for chronic migraine as 5 Units per site across 7 head and neck muscle areas and re-treated every 12 weeks, 50 Units per axilla injected intradermally for primary axillary hyperhidrosis, and up to 400 Units divided among affected muscles for adult upper limb spasticity. It says that in adults treated for one or more indications the maximum cumulative dose should not exceed 400 Units in a 3-month interval, and in children the total should not exceed the lower of 10 Units/kg body weight or 340 Units in a 3-month interval. (BOTOX (onabotulinumtoxinA) prescribing information, DailyMed (revised 11/2023))
The BOTOX Cosmetic label gives intramuscular total doses of 20 Units for glabellar lines (4 Units into each of 5 sites), 24 Units for lateral canthal lines (12 Units per side), 40 Units for forehead lines treated together with glabellar lines, and 26, 31 or 36 Units for platysma bands, depending on whether one or two bands are treated on each side. It says the safety and effectiveness of dosing more often than every 3 months have not been clinically evaluated. (BOTOX Cosmetic (onabotulinumtoxinA) prescribing information, DailyMed (revised 10/2024))
Doses reported in studies, exactly as the cited trial reported them. They are not personal dosing instructions. Population, route and schedule matter more than the number.
PREEMPT 1: 679 adults with chronic migraine. Dose: Minimum 155 Units across 31 fixed-site fixed-dose intramuscular injections in seven head and neck muscle areas, up to 195 Units across 39 injections, repeated every 12 weeks. Result: Pooled PREEMPT analysis reported a significantly greater reduction in headache days with onabotulinumtoxinA than placebo at 24 weeks
PREEMPT 2: 705 adults with chronic migraine. Dose: Minimum 155 Units across 31 fixed-site fixed-dose intramuscular injections in seven head and neck muscle areas, up to 195 Units across 39 injections, repeated every 12 weeks. Result: Met the primary endpoint of change from baseline in headache days versus placebo (Diener et al., Cephalalgia 2010)
M21-309: 408 adults with moderate to severe platysma prominence. Dose: Single intramuscular treatment of 26, 31 or 36 Units of onabotulinumtoxinA according to baseline severity, versus saline injection (FDA label). Result: Supported the 2024 platysma bands approval; investigator and participant assessments both favoured active treatment
M21-310: 426 adults with platysma prominence. Dose: Single intramuscular treatment of 26, 31 or 36 Units of onabotulinumtoxinA according to baseline severity, versus saline injection (FDA label). Result: Second of the two pivotal platysma studies supporting the 2024 approval
Minimum 155 Units across 31 fixed-site fixed-dose intramuscular injections in seven head and neck muscle areas, up to 195 Units across 39 injections, repeated every 12 weeks
Pooled PREEMPT analysis reported a significantly greater reduction in headache days with onabotulinumtoxinA than placebo at 24 weeks
Minimum 155 Units across 31 fixed-site fixed-dose intramuscular injections in seven head and neck muscle areas, up to 195 Units across 39 injections, repeated every 12 weeks
Met the primary endpoint of change from baseline in headache days versus placebo (Diener et al., Cephalalgia 2010)
Single intramuscular treatment of 26, 31 or 36 Units of onabotulinumtoxinA according to baseline severity, versus saline injection (FDA label)
Second of the two pivotal platysma studies supporting the 2024 approval
Doses in other published studies
Published studies not listed in the trials table above: smaller or unregistered human studies first, then animal and cell studies. Doses are shown exactly as each study reported them. Animal studies report weight-based doses, absolute amounts or concentrations; none translates directly to people, and none is converted here.
Subjects
Design
Dose
Finding
Source
Humans: 123 subjects with a history of two to eight moderate-to-severe migraine attacks per month, with or without aura (episodic migraine)
Double-blind, vehicle-controlled randomised study (BOTOX Migraine Clinical Research Group)
Single administration of vehicle or botulinum toxin type A (BOTOX), 25 U or 75 U, injected into multiple sites of pericranial muscles at the same visit; daily diaries for a 1-month baseline and 3 months after injection
The 25 U group had significantly fewer migraine attacks per month than vehicle, and only the 75 U group had a significantly higher rate of treatment-related adverse events than vehicle.
Prospective, double-blind, randomised, parallel-group dose-ranging study
Total dose of 20, 40, 60 or 80 U of botulinum toxin type A (BOTOX, BOTOX Cosmetic or Vistabel) in the glabellar area; assessed at baseline, 2 and 4 weeks, then monthly
The 40, 60 and 80 U doses were consistently more effective than 20 U, with a dose-dependent increase in response rate at maximum frown and duration of effect, and adverse event incidence did not increase with higher doses.
Humans: subjects with crow's feet (lateral canthal lines); number not stated in the abstract
Double-blind, randomised, placebo-controlled, parallel-group dose-response study
Single bilateral treatment of 18, 12, 6 or 3 U of botulinum toxin type A (Botox/Vistabel) or placebo injected into the lateral aspect of the orbicularis oculi muscle; the authors' conclusion expresses dose per side; ratings on day 7 and at 30-day intervals from day 30 to day 180
All doses improved crow's feet severity versus placebo with a dose-dependent magnitude and duration of effect, but no clear difference was seen between 18 U and 12 U, and adverse event incidence did not differ significantly from placebo.
Humans: 320 patients aged 18-75 with bilateral primary axillary hyperhidrosis randomised at 17 dermatology and neurology clinics in Belgium, Germany, Switzerland and the UK (307 completed)
Botulinum toxin type A (Botox) 50 U per axilla or placebo, given as 10-15 intradermal injections evenly distributed within the hyperhidrotic area of each axilla (defined by Minor's iodine starch test); outcomes at 4 weeks and week 16
Responders (at least 50% reduction in spontaneous axillary sweat production) were 94% versus 36% with placebo at 4 weeks and 82% versus 21% at week 16, with adverse events in 11% versus 5% (P>0.05).
Humans: 313 patients with idiopathic overactive bladder and urinary urgency incontinence (8 or more episodes a week and 8 or more micturitions daily at baseline) not adequately managed with anticholinergics
Intradetrusor onabotulinumtoxinA (BOTOX) 50, 100, 150, 200 or 300 U, or placebo; 7-day bladder diary; primary end point at week 12
Dose groups of 100 U or more showed durable efficacy, doses above 150 U contributed minimal additional improvement in symptoms, and changes in post-void residual urine volume and use of clean intermittent catheterisation were dose dependent.
Doses described in clinical or compounding practice
From FDA labels and documents, other regulators, published reviews and professional references, as each source states them. Unless a source says otherwise, these describe practice or proposals, not results tested in trials. Reading doses safely: how concentration and syringe markings work.
The BOTOX label recommends 100 Units injected into the detrusor for overactive bladder (which it calls the maximum recommended dose), 200 Units per treatment into the detrusor for adult detrusor overactivity associated with a neurologic condition, 155 Units given intramuscularly for chronic migraine as 5 Units per site across 7 head and neck muscle areas and re-treated every 12 weeks, 50 Units per axilla injected intradermally for primary axillary hyperhidrosis, and up to 400 Units divided among affected muscles for adult upper limb spasticity. It says that in adults treated for one or more indications the maximum cumulative dose should not exceed 400 Units in a 3-month interval, and in children the total should not exceed the lower of 10 Units/kg body weight or 340 Units in a 3-month interval. (BOTOX (onabotulinumtoxinA) prescribing information, DailyMed (revised 11/2023), FDA label)
The BOTOX Cosmetic label gives intramuscular total doses of 20 Units for glabellar lines (4 Units into each of 5 sites), 24 Units for lateral canthal lines (12 Units per side), 40 Units for forehead lines treated together with glabellar lines, and 26, 31 or 36 Units for platysma bands, depending on whether one or two bands are treated on each side. It says the safety and effectiveness of dosing more often than every 3 months have not been clinically evaluated. (BOTOX Cosmetic (onabotulinumtoxinA) prescribing information, DailyMed (revised 10/2024), FDA label)
The Global Aesthetics Consensus Group, which gives its dose recommendations for onabotulinumtoxinA, recommended lower minimum doses and fewer injection points than earlier guidelines. For example, it gives three to seven injection points for the glabella with a total of 12 to 40 units in most cases, and lower than 12 units when indicated. This is expert panel opinion (the paper grades its evidence as level V), and the paper notes that off-label aesthetic use is common. (Sundaram H et al. Global Aesthetics Consensus: Botulinum Toxin Type A. Plastic and Reconstructive Surgery, 2016, Peer-reviewed)
This review reports that studies in Asian individuals used total doses between 10 and 45 U of BoNT-A per side for masseter muscle prominence. It gives that range for BoNT-A in general and does not name the product used in each study. The authors write that in their experience "40 U or more of onabotulinumtoxinA per side" may suit moderate to severe cases better. They state that this use is not officially approved in any country, and Allergan funded the research and editorial support for the manuscript. (Wu Y, Zeng D, Wu S. Botulinum Toxin Type A for the Treatment of Masseter Muscle Prominence in Asian Populations. Aesthetic Surgery Journal Open Forum, 2023, Peer-reviewed)
Doses reported in online communities (untested)
Unverified, and not a recommendation. These are amounts people describe in online forums such as Reddit, collected so researchers can see how practice differs from the evidence. These forum accounts are not clinical evidence, even where they overlap studied doses. Products sold online as "research peptides" are not FDA approved, and their identity, purity and strength are not verified; they can be mislabeled, contaminated or wrongly dosed.
What people report
In the threads reviewed, migraine posts described the 155-Unit protocol given every 12 weeks, with some reporting 170 to 200 Units or more with extra sites in the head, neck or jaw. Cosmetic posts described about 14 to 60 Units for frown lines, forehead and crow's feet, repeated about every 3 to 6 months. Commenters disagreed on whether 50 or more Units at a first visit was normal. Reported problems included neck weakness, eyelid or brow droop, lower-face laxity after masseter treatment, and loss or lack of effect.
How this compares with the studies
Some migraine totals fall within the 155 to 195 Unit per-cycle range used in PREEMPT; higher totals and extra sites were not part of those trials. Cosmetic totals often combined several facial areas, so they do not match single study arms. Threads anchor migraine amounts to the 155-Unit protocol, and cosmetic posters often could not confirm which product or dilution they received; because Units are product-specific, exposure cannot be compared.
Open questions a study would need to answer
Do Units added outside the 31-site PREEMPT pattern, as described in some threads, change headache outcomes or rates of neck weakness and eyelid droop?
How often do reports of little or no effect at cosmetic doses reflect product identity, dilution or neutralising antibodies rather than the number of Units?
Is the loss of effect some people describe after repeated rounds of migraine treatment associated with measurable neutralising antibodies?
2024-04-16 · Safety alert: FDA alerted the public that counterfeit versions of Botox had been found in multiple states and administered to consumers. FDA listed identifiers of the counterfeit material, including an outer carton naming the active ingredient as "Botulinum Toxin Type A" rather than "OnabotulinumtoxinA" and unit strengths not made by the manufacturer. (source)
2024-04-15 · CDC media alert: CDC reported that, as of 15 April 2024, 19 people in nine states had harmful reactions after counterfeit botulinum toxin injections or injections given by unlicensed or untrained individuals or in non-healthcare settings. Nine were hospitalized and four were treated with botulism antitoxin. (source)
2026-10-08 · CDC report: CDC's MMWR described a Colorado medical spa that injected an unapproved botulinum toxin product (approved abroad, bought online) into 52 clients; three had short-lived neurological symptoms and none were hospitalised. The state issued a public health order and a licensing complaint. (source)
2025-11-05 · Warning letters: FDA announced 18 warning letters to owners of websites illegally marketing unapproved and misbranded botulinum toxin products in the United States. (source)
Side effects and warnings
Boxed warning: the toxin's effects can spread from the injection spot, hours to weeks later. Trouble swallowing or breathing can be life threatening. Deaths have been reported.
Spread can cause weakness, double or blurry vision, droopy eyelids, trouble speaking and loss of bladder control. The risk of swallowing and breathing problems is highest in children treated for muscle stiffness (spasticity).
Common side effects depend on the use. For migraine: neck pain and headache. For facial lines: droopy eyelids or brows. For bladder uses: urine infections, pain when passing urine, and trouble emptying the bladder, which may need a tube (catheter).
Serious allergic reactions can happen. These include anaphylaxis (a severe, sudden allergic reaction), hives and swelling.
It should not be used by people allergic to any botulinum toxin product or its ingredients. It should not be used where there is an infection at the injection spot.
Some antibiotics (aminoglycosides) and other botulinum toxin products may make its effects stronger. Muscle relaxants may cause too much weakness. Anticholinergic drugs may have stronger effects of their own.
Full lists are in the .
Reported side effects
Boxed warning: the effects of BOTOX and all botulinum toxin products may spread from the area of injection to produce symptoms consistent with botulinum toxin effects. Symptoms have been reported hours to weeks after injection, swallowing and breathing difficulties can be life threatening, and there have been reports of death
Dysphagia and breathing difficulties, with the greatest reported risk in children treated for spasticity
Spread-of-effect symptoms including asthenia, generalised muscle weakness, diplopia, blurred vision, ptosis, dysarthria and loss of bladder control
Hypersensitivity reactions, including anaphylaxis, serum sickness, urticaria and angioedema
Cervical dystonia: dysphagia, upper respiratory infection, neck pain and headache
Chronic migraine: neck pain and headache
Axillary hyperhidrosis: injection site pain and haemorrhage, non-axillary sweating, pharyngitis
Bladder indications: urinary tract infection, dysuria and urinary retention; the label warns that patients may require catheterisation
Glabellar and other facial line indications: eyelid ptosis, brow ptosis and injection site reactions
Corneal exposure and ulceration reported with reduced blinking after injection near the eye
Interactions
Aminoglycoside antibiotics and other agents interfering with neuromuscular transmission may potentiate the effect of botulinum toxin
Anticholinergic drugs may potentiate systemic anticholinergic effects
Other botulinum neurotoxin products administered concurrently or within several months may potentiate the effect
Muscle relaxants may produce excessive neuromuscular weakness
Contraindications
Known hypersensitivity to any botulinum toxin product or to any component of the formulation
Infection at the proposed injection site
Intradetrusor injection: urinary tract infection, and urinary retention or post-void residual volume above 200 mL in patients not routinely catheterising
Storage
Unopened: The label directs storage of unopened vials in a refrigerator at 2 to 8 °C.
Reconstituted / in use: The label directs that reconstituted product be stored in a refrigerator at 2 to 8 °C and administered within 24 hours.
Product characteristics
Form: Sterile vacuum-dried powder in single-dose vials, reconstituted with sterile preservative-free 0.9% sodium chloride injection before intramuscular, intradetrusor or intradermal administration as specified by the label
Stability: The label states that potency Units of BOTOX are specific to the preparation and assay method used and are not interchangeable with other botulinum toxin products
Compound information
Purified neurotoxin type A produced by fermentation of Clostridium botulinum type A (Hall strain). The core neurotoxin is a 150 kDa dichain zinc endopeptidase whose light chain cleaves SNAP-25. UniProt entry P0DPI1 (BXA1_CLOBH). The approved product is formulated with human albumin and sodium chloride.
Molecule, patents, enforcement history, full trial tables and compound details are in the .
Common questions
What is OnabotulinumtoxinA?
OnabotulinumtoxinA is the generic name of a botulinum toxin type A product. In the United States it is sold as Botox. For cosmetic uses it is sold as Botox Cosmetic. It is a protein made by a germ called Clostridium botulinum. The protein is cleaned up and supplied as a powder. A clinician mixes the powder with salt water (saline) before the injection.
Is OnabotulinumtoxinA FDA approved?
FDA approved as Botox and Botox Cosmetic, for uses including chronic migraine prevention, eye-muscle spasms, and frown lines, crow's feet, forehead lines and neck bands.
What have studies found?
In two large migraine trials (PREEMPT 1 and 2), people who got Botox had fewer headache days than those who got a placebo. Two neck band trials (M21-309 and M21-310) supported the 2024 approval.
Other studies found it helped frown lines, crow's feet, heavy armpit sweating and overactive bladder. For armpit sweating, 94% of people had at least 50% less sweat at 4 weeks, versus 36% with placebo. For the bladder, doses of 100 U or more kept working.
How was it dosed in studies?
The PREEMPT 1 and 2 trials are finished. They included 679 and 705 adults with long-term (chronic) migraine. They compared onabotulinumtoxinA with a dummy treatment (placebo). People got at least 155 Units as 31 injections into muscle. The injections went into set spots across seven head and neck areas. Some got up to 195 Units across 39 injections. This was repeated every 12 weeks. The M21-309 and M21-310 trials are also finished. They included 408 and 426 adults with prominent neck bands (platysma prominence). People were assigned by chance to one treatment into muscle, or to salt water (saline). The dose was 26, 31 or 36 Units, based on how severe the bands were at the start. Other studies that assigned people by chance tested 25 U or 75 U into head muscles against an inactive injection. One tested 50 U per armpit, injected into the skin, against placebo. Another tested 20, 40, 60 and 80 U in the frown-line area.
What are the side effects and warnings?
Boxed warning: the toxin's effects can spread from the injection spot, hours to weeks later. Trouble swallowing or breathing can be life threatening. Deaths have been reported.
Spread can cause weakness, double or blurry vision, droopy eyelids, trouble speaking and loss of bladder control. The risk of swallowing and breathing problems is highest in children treated for muscle stiffness (spasticity).
Common side effects depend on the use. For migraine: neck pain and headache. For facial lines: droopy eyelids or brows. For bladder uses: urine infections, pain when passing urine, and trouble emptying the bladder, which may need a tube (catheter).
Serious allergic reactions can happen. These include anaphylaxis (a severe, sudden allergic reaction), hives and swelling.
It should not be used by people allergic to any botulinum toxin product or its ingredients. It should not be used where there is an infection at the injection spot.
Some antibiotics (aminoglycosides) and other botulinum toxin products may make its effects stronger. Muscle relaxants may cause too much weakness. Anticholinergic drugs may have stronger effects of their own.
References
This page summarises the published sources below. PeptideBasics101 does no original research. Trial doses and results are reported as the cited study or label reported them. Sources can themselves be wrong or superseded; if you find a statement here that does not match its source, please tell us through our corrections process. Sources were last checked on 2026-11-01.
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