The results of our three patients would indicate that injections of greater than 600 units of Botox with follow-up injections occurring every three months may lead to an increased risk. It may be more likely that risk for systemic effects is related to total injection dose and injection frequency.

A review of the literature and reported cases indicate that risk of developing systemic effects does not appear to be related to dose based on body weight.

Previously reported occurrences are discussed, and three new cases of patients who developed systemic weakness following administration of BoNT-A (Botox®), despite having tolerated similar injections on several prior occasions, are presented. While most side effects are mild, systemic effects, manifested by generalized weakness distant from the site of injection, have been reported. The use of intramuscular injections of Botulinum neurotoxin A (BoNT-A) is common in the treatment of hypertonicity and movement disorders.