Neuromuscular Blocking Agent (Botulinum Toxin) Pregnancy: Avoid — insufficient data; theoretical risk of systemic spread; no established safe dose; localised injection may carry lower risk but avoid unless clearly necessary

Botulinum Toxin Type A (ENT)

Brand names: Botox, Dysport, Xeomin

Adult dose

Dose: Sialorrhoea: 30–100 units into each parotid gland (50 units per parotid is typical); Frey's syndrome: 2.5–5 units intradermally per cm² of affected area; Spasmodic dysphonia: 0.5–2.5 units into thyroarytenoid muscle

Route: Intraglandular / intradermal injection (specialist)

Frequency: Every 3–6 months (as effect wanes)

Max: Varies by indication and brand

Units are NOT interchangeable between brands (Botox ≠ Dysport ≠ Xeomin units); specialist-only procedure; ultrasound guidance recommended for parotid injections

Paediatric dose

Dose: Sialorrhoea (e.g. cerebral palsy): 20–30 units/parotid; specialist use units/kg

Route: Intraglandular

Frequency: Every 4–6 months

Max: Varies by weight and indication

Paediatric sialorrhoea: NICE TA107 (Botox licensed for chronic sialorrhoea in neurological conditions ≥2 years)

Dose adjustments

Renal

No dose adjustment required — minimal systemic absorption

Hepatic

No dose adjustment required

Paediatric weight-based calculator

Patient weight (kg)

Paediatric sialorrhoea: NICE TA107 (Botox licensed for chronic sialorrhoea in neurological conditions ≥2 years)

Clinical pearls

Frey's syndrome (auriculotemporal syndrome): aberrant reinnervation of parotid skin sweat glands by parasympathetic fibres after parotidectomy — flushing and sweating on eating (gustatory sweating); intracutaneous botulinum toxin is first-line treatment (Minor's starch-iodine test confirms diagnosis and maps injection area)
Sialorrhoea in neurological disease (ALS, cerebral palsy, Parkinson's): intraglandular botulinum toxin into parotid ± submandibular glands achieves 3-6 months of salivary flow reduction — ultrasound guidance improves accuracy and reduces dysphagia risk
Spasmodic dysphonia (adductor type): laryngeal EMG-guided injection into thyroarytenoid muscle — produces a temporary breathy voice period for ~2-4 weeks before therapeutic effect of reduced voice breaks begins; lasts 3-4 months; highly effective (>90% improvement)
Brand non-equivalence: Botox (onabotulinumtoxinA), Dysport (abobotulinumtoxinA), and Xeomin (incobotulinumtoxinA) have different unit systems — Dysport doses are approximately 3× Botox units for equivalent effect; prescribe by brand name always
MHRA 2012 guidance: botulinum toxin products are prescription-only medicines; cosmetic use requires face-to-face medical consultation; all therapeutic indications require specialist assessment

Contraindications

Neuromuscular junction disorders (myasthenia gravis, Lambert-Eaton syndrome)
Active infection at injection site
Known hypersensitivity to botulinum toxin or human albumin excipient

Side effects

Parotid injection: dry mouth (anticholinergic — dose-dependent), transient dysphagia, injection site pain
Frey's syndrome injection: mild bruising, transient skin effects
Spasmodic dysphonia: breathy voice, dysphagia (if spread to pharyngeal muscles)

Interactions

Aminoglycosides (gentamicin) — potentiate neuromuscular blockade
Anticholinergic drugs — additive dry mouth with parotid injection

Monitoring

Clinical response duration (schedule re-injection at effect wearing off)
Swallowing assessment (dysphagia risk with parotid/submandibular injections)
Dry mouth severity
Voice quality (spasmodic dysphonia)

Reference: BNFc; BNF 90; MHRA Botulinum Toxin Guidance 2012; NICE TA107 (chronic sialorrhoea); Borodic et al. Laryngoscope 1992 (spasmodic dysphonia); BAO-HNS Frey's Syndrome Guideline. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways