Botulinum toxin type A

How it works

It cleaves the SNARE protein SNAP-25 at cholinergic nerve terminals, blocking acetylcholine release and producing temporary, localised muscle relaxation.

Prescribing in practice

• An MHRA warning highlights the risk of toxin spread beyond the injection site causing dysphagia, aspiration and breathing difficulties, which can be life-threatening, particularly in those with pre-existing neuromuscular disease.
• Product preparations and units are NOT interchangeable, so the specific brand and its unit definition must always be specified to avoid serious dosing errors.
• Use with caution in disorders of neuromuscular transmission such as myasthenia gravis or Eaton-Lambert syndrome, which may exaggerate the systemic effect.

Monitoring

Monitor clinically for local and distant spread of effect (notably swallowing and respiratory function) and reassess muscle tone and function before each re-treatment cycle.

Counselling the patient

• The effect is temporary and wears off over weeks to months, requiring repeat injection.
• Seek urgent help for difficulty swallowing, speaking or breathing after treatment.
• Mild local weakness, bruising or ptosis near the injection site can occur.

Evidence & guidelines

Botulinum toxin type A is a NICE-recognised treatment for focal dystonias, spasticity and chronic migraine, supported by randomised trial evidence in each indication.