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Botulism Following Botulinum Toxin Injection

Introduction
Pharmaceutical grade botulinum toxin type A or B (though B is not registered in HK) is being used for
cosmetic and therapeutic purposes. It is produced from culture of Clostridium Botulinum.

Botulinum toxin (BTX) irreversibly blocks the release of acetylcholine from presynaptic neurons and
prevents nerve impulse transmission. It acts at neuromuscular junctions, autonomic ganglia and
parasympathetic nerve terminals.

Adverse drug reactions (ADR) and toxicity of overdose
Onset of adverse drug reactions (ADR) after therapeutic dose use is expected to be delayed for 2‐3
days after injection.

Common BTX adverse effects
Commonly reported (1‐10%) adverse effects after therapeutic dose use include: fatigue,
influenza‐like‐illness and headache. The following adverse effects which are localized to the site of
injection could also occur: eyes discomfort, ptosis, eyelid oedema, increased or decreased lacrimation,
blurred vision, injection site pain / bruising / swelling / reddening, muscles pain, muscle twitching,
muscle weakness adjacent to the area of injection, dysphagia, dysphonia, gait disturbance, diarrhoea,
urinary incontinence.

Rare and life‐threatening BTX adverse effect / toxicity
Spreads of BTX beyond the site of local injection (botulism) have been very rarely reported in causing
generalized weakness, dysphagia, aspiration pneumonia, flaccid paralysis, respiratory muscle paralysis,
autonomic neuropathy etc. In rare occasion after receiving massive BTX dose, patient can present
with botulism 1‐2 days after exposure.

Botulism classically presented with progressive descending symmetrical flaccid paralysis, starting with
dysphagia, dysphonia, ptosis and blurred vision, followed by respiratory muscles paralysis. Autonomic
neuropathy may lead to postural hypotension, dry mouth and cardiovascular, gastrointestinal and
urinary autonomic dysfunction. Mental state and sensory functions are preserved.

Diagnosis
BTX adverse effects and toxicity is mainly a clinical diagnosis. Monitor bedside spirometry (e.g.: peak
expiratory flow rate) and blood gas in severe cases. Nerve conduction study in patient with botulism
typically shows reduced motor potentials amplitude with normal conduction velocity and normal
sensory potentials.

Management
In contrast to other forms of botulism (foodborne, infant, wound or inhalation botulisms), the
mainstay management of botulism following botulinum toxin injection is supportive. Monitor for
weakness progression and respiratory failure. Severe cases may require intubation and mechanical
ventilation.

Botulinum antitoxin cannot reverse established muscle weakness. It is generally NOT indicated in
cases presented with common BTX adverse effects.

In rare incidents of severe poisoning presented with progressive generalized weakness, swallowing
and breathing difficulty, the use of antitoxin should be considered. Please contact Hong Kong Poison
Information Centre (Tel: 2772 2211) or Prince of Wales Hospital Poison Treatment Centre (Tel: 2632
6209) for management advice.

Produced by the Hong Kong Poison Control Network
June 2016