Complications/Adverse Reactions

Side effects most often reported during clinical trials included headache, respiratory infection, blepharoptosis, nausea, and flu syndrome. Less frequently occurring adverse reactions included pain in the face and erythema at the injection site. In rare cases, botulinum injections have caused transient relaxation of injected or nearby muscles, resulting in blepharoptosis (eyelid ptosis) or asymmetry of facial expression. Blepharoptosis is a short-lived side effect that can be reversed by treating with an alpha-1-adronergic agent. Asymmetry of facial expression can be corrected by relaxing the contralateral muscles. Unlike blepharoptosis, asymmetry of facial expression can be a prolonged side effect. The risk of any side effects depends on which muscles are injected. Because treatment is completely reversible, side effects related to excessive relaxation are temporary, lasting only days or weeks [14]. The human median lethal dose (LD50) is estimated to be 40 U/kg (2,800 U for an average 70-kg individual) [34].