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Neurotoxin — Therapeutic / Cosmetic Pregnancy: There are no adequate data from the use of botulinum toxin type A in pregnant women. Studies in animals have shown reproductive toxicity and the potential risk for humans is unknown. BOTOX is not recommended during pregnancy and in women of childbearing potential not using contraception. Breast-feeding: there is no information on whether BOTOX is excreted in human milk and its use during breast-feeding cannot be recommended. Fertility: there are no adequate data on the effects on fertility in women of childbearing potential; studies in male and female rats have shown fertility reductions.

Botulinum Toxin Type A

Brand names: Botox (onabotulinumtoxinA), Dysport (abobotulinumtoxinA), Bocouture (incobotulinumtoxinA), Azzalure

A purified neurotoxin from Clostridium botulinum injected to produce localised muscle relaxation, used for therapeutic indications such as focal dystonia, spasticity, hyperhidrosis and chronic migraine, and for facial aesthetic and scar treatment in plastics.

Adult dose

Dose: BOTOX (onabotulinumtoxinA) 100 Allergan Units per vial. Allergan Units are NOT interchangeable with the units of any other botulinum toxin product. ADULT DOSES BY INDICATION. AESTHETIC (temporary improvement in appearance, when the severity has an important psychological impact): GLABELLAR LINES - 0.1 ml (4 Units) into each of 5 sites (2 in each corrugator muscle, 1 in procerus), total 20 Units. CROW'S FEET LINES - 0.1 ml (4 Units) into each of 3 sites per side (6 sites) of the lateral orbicularis oculi, total 24 Units in 0.6 ml (12 Units per side); treated together with glabellar lines, 24 + 20 = 44 Units in 1.1 ml. FOREHEAD LINES - 0.1 ml (4 Units) into each of 5 frontalis sites, total 20 Units in 0.5 ml; with glabellar lines 40 Units/1.0 ml; with glabellar and crow's feet lines 64 Units (20 + 20 + 24). PLATYSMA PROMINENCE - 2 Units/0.05 ml into each of 4 jawline sites per side (16 Units in 8 sites) plus 1 Unit/0.025 ml into each of 5 sites along each vertical neck band, 1 to 2 bands per side: total 26 Units (18 sites; 1 band each side), 31 Units (23 sites; 1 band on one side and 2 on the other) or 36 Units (28 sites; 2 bands each side). SEVERE PRIMARY AXILLARY HYPERHIDROSIS not controlled by topical antiperspirants - 50 Units intradermally into each axilla, evenly distributed over multiple sites about 1-2 cm apart, 0.1-0.2 ml per site. NEUROLOGICAL (specialist use): adult upper limb spasticity - up to 400 Units divided among the affected muscles; adult lower limb spasticity - 300 Units to 400 Units divided among up to 6 muscles; blepharospasm/hemifacial spasm - initial 1.25-2.5 Units (0.05-0.1 ml) at each site, into the medial and lateral orbicularis oculi of the upper lid and the lateral orbicularis oculi of the lower lid; cervical dystonia - tailored to the individual patient, with per-muscle Unit ranges by dystonia type in the SPC; chronic migraine prophylaxis - 155 Units to 195 Units as 0.1 ml (5 Units) injections to 31 and up to 39 sites. BLADDER (adults not adequately managed with anticholinergics): overactive bladder - 100 Units as 0.5 ml (5 Units) injections across 20 sites in the detrusor muscle; urinary incontinence due to neurogenic detrusor overactivity - 200 Units as 1 ml (~6.7 Units) injections across 30 sites in the detrusor muscle.
Route: Glabellar, crow's feet and forehead lines: injection into the named muscles (corrugator and procerus; lateral orbicularis oculi; frontalis). Platysma: superficially and intramuscularly. Axillary hyperhidrosis: intradermal. Spasticity, blepharospasm/hemifacial spasm and cervical dystonia: injection into the affected muscles. Chronic migraine: intramuscular. Overactive bladder / neurogenic detrusor overactivity: into the detrusor via a flexible or rigid cystoscope, avoiding the trigone and base.
Frequency: Glabellar, crow's feet and forehead lines, platysma prominence: treatment intervals not more frequent than every 3 months. Axillary hyperhidrosis: not repeated more frequently than every 16 weeks (clinical improvement generally within the first week and persisting 4-7 months). Spasticity: re-injection no sooner than 12 weeks after the previous injection. Blepharospasm/hemifacial spasm: each treatment lasts approximately three months; normally no additional benefit from treating more frequently than every three months. Cervical dystonia: treatment intervals of less than 10 weeks are not recommended. Chronic migraine: re-treatment every 12 weeks. Overactive bladder / neurogenic detrusor overactivity: reinjection no sooner than 3 months from the prior bladder injection.
Max: Adults treated for multiple indications: cumulative maximum 400 Units in a 12-week interval. Glabellar and crow's feet lines: do not exceed 4 Units per injection site or the number of sites (to reduce the risk of eyelid ptosis); glabellar lines, if the dose proves insufficient, a second session may adjust the total up to 40 or 50 Units. Platysma prominence: no more than 2 Units per jawline site and 1 Unit per vertical-band site; total not to exceed 26, 31 or 36 Units as above. Axillary hyperhidrosis: doses other than 50 Units per axilla cannot be recommended. Upper limb spasticity: 400 Units in total; lower limb spasticity: 400 Units in total. Blepharospasm: initial dose not to exceed 25 Units per eye; total not to exceed 100 Units every 12 weeks. Cervical dystonia: no more than 50 Units at any one injection site, no more than 100 Units to the sternomastoid, no more than 200 Units in total for the first course, up to a maximum total of 300 Units.
SOURCE AND SCOPE: UK SPC via MHRA Products — BOTOX 100 Units per vial (PL410420057), AbbVie Ltd. This is a class page, but the card covers BOTOX only; Dysport, Bocouture and Azzalure use different, non-interchangeable units and are NOT covered. Never convert Units between products. To be given only by an appropriately qualified healthcare practitioner with expertise in the relevant indication and equipment, in line with national guidelines; single use only. Generally valid optimum dose levels and numbers of injection sites have not been established for all indications: optimum doses are found by titration but the recommended maximum dose should not be exceeded; initial dosing in treatment-naive patients should start at the lowest recommended dose for the indication. Scar management, wound-tension reduction and drooling are not among the indications in SPC section 4.1 and no dose is given for them. NOT REPRODUCED: the SPC's per-muscle tables and injection-site diagrams (upper limb spasticity per-muscle Units, cervical dystonia by dystonia type, chronic migraine per-muscle Units, bladder injection diagrams); use the SPC for these. Reconstitution (SPC section 6.6) was not retrieved: bladder solutions are 100 Units/10 ml (overactive bladder) and 200 Units/30 ml (neurogenic detrusor overactivity); reconstitute only as the SPC directs (the SPC reports one fatal anaphylaxis after BOTOX was inappropriately diluted with 5 ml of 1% lidocaine). Neurogenic detrusor overactivity is licensed after subcervical spinal cord injury or multiple sclerosis; no urodynamic data beyond 2 treatments, so patients should not receive multiple treatments in the event of limited symptomatic improvement. AESTHETIC TECHNIQUE: use a sterile 30 gauge needle; ensure the product is not injected into a blood vessel; for glabellar lines place a thumb or finger firmly below the orbital rim, orient the needle superiorly and medially, avoid injections near levator palpebrae superioris and inject the corrugator at least 1 cm above the arch of the eyebrows; for crow's feet inject temporal to the orbital rim with the bevel up and away from the eye; for platysma inject at least 1 cm inferior to the lower mandibular border and not into structures deep to the platysma (to reduce facial paresis and dysphagia). Efficacy and safety of repeat aesthetic injections beyond 12 months have not been evaluated. In case of treatment failure or diminished effect after repeat injections (no significant clinical improvement at one month), investigate the cause and use alternative treatment methods if it persists; a second session needs a three-month interval. SPASTICITY / BLEPHAROSPASM: localise muscles with EMG, nerve stimulation or ultrasound (spasticity); at blepharospasm repeat sessions the dose may be increased up to two-fold if the response is insufficient, with little benefit from more than 5 Units per site. ELDERLY: dosages are the same as for younger adults; start at the lowest recommended dose for the indication and treat with caution when there is significant medical history or concomitant medication. CHILDREN: see paedDose; no posology can be recommended for any other paediatric indication.

Paediatric dose

Dose: Focal spasticity associated with cerebral palsy, children 2 years of age and older (upper limb: elbow, wrist and hand; lower limb: ankle and foot in ambulant children), as a total divided among the affected muscles: upper limb 3 Units/kg to 6 Units/kg body weight; lower limb 4 Units/kg to 8 Units/kg body weight
Route: Injection into the affected muscles (localisation by EMG, nerve stimulation or ultrasound is recommended)
Frequency: Re-injection no sooner than 12 weeks after the previous injection, when the clinical effect has diminished
Max: Upper limb: total per treatment session not to exceed 6 Units/kg body weight or 200 Units, whichever is lower. Lower limb: total per treatment session not to exceed 8 Units/kg body weight or 300 Units, whichever is lower. Upper and lower limbs, or both lower limbs, treated together: total not to exceed the lower of 10 Units/kg body weight or 340 Units in a 12-week interval (this also applies when treating paediatric patients for multiple indications).
These are the SPC's own paediatric figures for this one indication, not scaled from the adult dose; they are per-session totals given as a per-kg range, so no single per-kg value is stored. The SPC gives no figure below 2 years of age and states that no posology recommendation can be made for any paediatric indication other than focal spasticity associated with cerebral palsy. To be given only by practitioners experienced in assessing and treating paediatric focal spasticity, as part of a structured rehabilitation programme; BOTOX is not intended to substitute for usual standard-of-care rehabilitation. Local anaesthesia, or local anaesthesia with minimal or moderate sedation, may be used per local practice; safety and efficacy under general anaesthesia or deep sedation/analgesia have not been evaluated. Per-muscle dosing tables are in the SPC and not reproduced. Verify against a children's formulary and specialist advice before use.

Dose adjustments

Renal

Not stated — no renal-impairment dosing statement appears in the SPC text that was retrieved.

Hepatic

Not stated — no hepatic-impairment dosing statement appears in the SPC text that was retrieved.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Known hypersensitivity to botulinum toxin type A or to any of the excipients
  • Presence of infection at the proposed injection site(s)
  • Bladder disorders: urinary tract infection at the time of treatment
  • Bladder disorders: acute urinary retention at the time of treatment, in patients who are not routinely catheterising
  • Bladder disorders: patients not willing and/or able to initiate catheterisation post-treatment if required
  • Bladder disorders: presence of bladder calculi

Side effects

  • Spread of toxin effect distant from the site of administration, sometimes resulting in death and in some cases associated with dysphagia, pneumonia and/or significant debility; symptoms are consistent with the mechanism of action and have been reported hours to weeks after injection
  • Iatrogenic botulism has been reported following injection of botulinum toxin products
  • Exaggerated muscle weakness, including with therapeutic doses; local muscle weakness is the expected pharmacological action, but weakness of adjacent muscles and/or muscles remote from the injection site has been reported
  • Eyelid ptosis (glabellar and crow's feet injections near the levator palpebrae superioris, or blepharospasm injections) and diplopia (medial lower lid injections in blepharospasm) are named complications to avoid by technique
  • Facial paresis and dysphagia are named risks of platysma injections placed too close to or deep to the platysma
  • Dysphagia has been reported after injection to sites other than the cervical musculature
  • Injection-related: localised pain, inflammation, paraesthesia, hypoaesthesia, tenderness, swelling/oedema, erythema, localised infection, bleeding and/or bruising; needle-related pain or anxiety may cause vasovagal responses, including transient symptomatic hypotension and syncope
  • Fever and flu syndrome have been reported after injections of botulinum toxin
  • Rare serious and/or immediate hypersensitivity reactions including anaphylaxis, serum sickness, urticaria, soft tissue oedema and dyspnoea
  • Pneumothorax associated with the injection procedure has been reported after administration near the thorax
  • Formation of neutralising antibodies (one reason the recommended dosages and frequencies of administration should not be exceeded)
  • The SPC section 4.4 and 4.8 text was cut off at the source-fetch limit, so the frequency-by-indication tables are not available and this list is not complete

Interactions

  • Aminoglycoside antibiotics or spectinomycin, or other medicines that interfere with neuromuscular transmission (e.g. neuromuscular blocking agents): the effect of botulinum toxin may theoretically be potentiated
  • Other botulinum toxins: the effect of different botulinum neurotoxin serotypes given at the same time or within several months of each other is unknown; excessive neuromuscular weakness may be exacerbated by another botulinum toxin given before the effects of a previous one have resolved
  • Overactive bladder: no data on concomitant use of anticholinergics with BOTOX injections
  • No interaction studies have been performed; no interactions of clinical significance have been reported

Monitoring

  • Advise patients and caregivers to seek immediate medical advice if there are signs or symptoms of spread of the toxin effect or if swallowing, speech or respiratory disorders arise
  • Side effects can occur despite previous injections being well tolerated: take caution at every administration
  • Use with extreme caution and close supervision in patients with defective neuromuscular transmission (e.g. myasthenia gravis, Lambert-Eaton syndrome), peripheral motor neuropathic diseases (e.g. amyotrophic lateral sclerosis, motor neuropathy) or underlying neurological disorders; extreme caution in patients with a history of dysphagia and aspiration
  • Caution in the presence of inflammation at the proposed injection site(s) or when excessive weakness or atrophy is present in the target muscle
  • Understand the relevant anatomy (and any changes from prior surgery) before injecting and avoid vulnerable anatomic structures; caution when injecting near the lung, particularly the apices
  • Overactive bladder: observe the patient for at least 30 minutes post-injection and until a spontaneous void has occurred, and leave the visualisation saline in the bladder so the patient can demonstrate the ability to void before leaving the clinic; for both bladder indications see SPC section 4.4 for patient preparation and monitoring (not retrieved here)
  • Elderly and debilitated patients should be treated with caution; dose selection usually starts at the low end of the dosing range
  • Sedentary patients should be cautioned to resume activity gradually
  • If a hypersensitivity reaction occurs, stop further injection and institute appropriate medical therapy such as epinephrine immediately
  • Treatment failure: if there is no significant clinical improvement at one month after injection, verify the action of the toxin on the injected muscle(s) (EMG in a specialist setting may be used) and analyse the cause, such as choice of muscles, insufficient dose, poor technique, fixed contracture, weak antagonists or neutralising antibodies
  • Do not use for unapproved indications or injection sites: serious adverse events including fatal outcomes have been reported after off-label injection into salivary glands, the oro-lingual-pharyngeal region, oesophagus and stomach

Clinical monograph

How it works

It cleaves SNAP-25, blocking presynaptic release of acetylcholine at the neuromuscular junction and at cholinergic autonomic nerve endings, producing temporary, reversible chemodenervation.

Prescribing in practice

  • Toxin may spread beyond the injection site causing distant muscle weakness, dysphagia and breathing difficulty, so it must be administered only by trained clinicians and units are not interchangeable between brands.
  • Avoid in infection at the proposed injection site and in known hypersensitivity, and use with caution in neuromuscular disorders such as myasthenia gravis.
  • Effects are temporary and wear off over weeks to months, requiring repeat treatment.

Monitoring

Monitor for the intended functional response and for signs of unwanted local or distant muscle weakness after each treatment cycle.

Counselling the patient

  • The effect develops over several days and is temporary, lasting some months.
  • Seek urgent help for swallowing, speaking or breathing difficulty, or generalised weakness.
  • Avoid rubbing the treated area immediately after injection.

Evidence & guidelines

The MHRA highlights that botulinum toxin products are not interchangeable and carry a risk of toxin spread, reflected in product labelling.

Reference: MHRA Botulinum Toxin Guidance; BAPRAS (British Association of Plastic, Reconstructive and Aesthetic Surgeons) Scar Management Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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