There are subtypes of type A botulinum toxin, two of which (Botox and Dysport) are commonly used to treat sialorrhoea. These subtypes have different biological activities; thus, dose adjustments must be made accordingly (Botox 1:3 Dysport).46

Has a greater propensity for autonomic effects.46

Has a higher immunogenicity and so repeated use may have a greater risk of antibody-induced failure.47 48

Commonly used doses in trials to date: 100 MU of Botox, 250 MU of Dysport, 2500 MU of NeuroBloc.

Doses should be divided between the submandibular and parotid glands, with the parotid receiving a greater fraction of the total dose.

Optimal therapeutic dose not established. Titrate as appropriate.49

Confirms accurate delivery of the toxin

Practical and largely considered safe (figure 3)

Meta-analysis data supporting its clinical efficacy

Effective in patients with symptoms resistant to medications

Effects last for 3–6 months

Fewer side effects than anticholinergic medication

Minimally invasive

May decrease risk of aspiration pneumonia in neurologically impaired children.51

Common adverse effects: xerostomia, thickened bronchial secretions and viscous saliva, difficulty chewing and pain at the site of injection. Reverse slowly as toxin effect wears off.52

Dysphagia is a rare side effect.53

Repeat injections may result in antibody formation and fading efficacy.49

Patients with motor neurone disease may be more prone to adverse effects and shorter benefit duration compared with those with Parkinson’s disease.

Old age may be associated with longer benefit duration.53