Adult Spasticity of the Arm Post-Stroke:
Muscle weakness is the most commonly reported adverse event in clinical studies and in the literature, for this patient population. In the 2 pivotal studies using Dysport for arm spasticity post-stroke, the most frequent adverse events were infection (8.2%), flu syndrome (6.1%), dry mouth, myasthenia, pain, constipation, diarrhoea, pharyngitis and somnolence (each with an incidence of 4.1%). The majority of events resolved within 2 weeks.
Dysphagia has been reported at doses in excess of 2700 units given in 1 dose or when given as a divided dose 12 weeks apart. No cases were reported in pivotal studies.
Paediatric Cerebral Palsy Spasticity:
Adverse event incidence has been assessed by 3 prospective studies involving 142 patients treated with Dysport and 75 patients treated with placebo. Adverse events with an incidence of ≥5% following Dysport treatment were leg pain (8%), pharyngitis (8%), accidental injury (7%), bronchitis (6%) and fever (6%). Those with an incidence of 1-5% were viral infection (5%), infection (4%), rhinitis (4%), convulsion (4%), upper respiratory tract infection (4%), asthenia (3%), asthma (3%), cough (3%), vomiting (3%), cold (2%), diarrhoea (2%), urinary incontinence (2%), abnormal gait (1%), gastroenteritis (1%), laryngitis (1%) and somnolence (1%).
The incidence of many of these adverse events (pharyngitis, bronchitis, fever, viral infection, rhinitis, upper respiratory tract infection, cough, vomiting, cold) was similar in placebo-treated patients and probably indicates the typical spectrum of illness in a paediatric population. Also, the incidence of convulsions was identical in placebo-treated patients and reflects one of the most frequent concomitant problems associated with cerebral palsy.
The incidence of accidental injury (falls) demonstrated the biggest difference with placebo-treated patients (1%), and it is likely that these adverse events are due to overweakening of the target muscle and/or the local spread of Dysport to other muscles involved in ambulation and balance. The reports of abnormal gait may also be the result of such an effect. Another local side effect was leg pain, predominantly, calf pain. Although this pain appears to be distinct from any pain experienced from the injection itself, it was also reported for 5% of placebo treatments. Asthenia and urinary incontinence were associated with higher doses of Dysport (20-30 units/kg) and may be the result of systemic spread of the toxin.
Side effects may occur mainly from deep or misplaced injections temporarily paralysing other nearby muscle groups. The injections have been associated with a burning sensation which lasts for 1-2 min after injection. In patients treated for torticollis, dysphagia is the most frequently reported adverse event. In a double-blind, placebo-controlled trial, the incidence of dysphagia was 29% following treatment with Dysport 500 units and 10% in the placebo group. This appears to be dose-related and occurs most frequently following injection into the sternomastoid muscle. A soft diet may be required until symptoms resolve. In those patients severely affected, laryngoscopy has identified pooling of saliva. Aspiration may occur rarely and be of potential concern in those patients with preexisting respiratory problems. Less frequently reported events include weakness of the neck muscles, dryness of mouth and voice changes. A more generalised weakness and visual disturbances (including diplopia and blurred vision) have occasionally been reported. Respiratory difficulties have been noted on rare occasions in association with high doses. These side effects may be expected to resolve within 2-4 weeks. Allergic reactions eg, skin rashes and influenza-like symptoms have occasionally been noted.
Blepharospasm and Hemifacial Spasm:
Side effects may occur from deep or misplaced injections of Dysport, temporarily paralysing other nearby muscle groups. They may also occur from exacerbation of preexisting eyelid abnormalities or from an initial overcorrection. Ptosis is the most common unwanted effect.
A few patients may also experience diplopia or symptoms from spread of the paralytic effect to midfacial muscles.
These side effects may be expected to resolve within 2-4 weeks. Keratitis and dry eyes due to reduced blinking have also been reported for which the use of artificial tears could be considered. Minor bruising and lid swelling may occur but are short-lived. Reversible external ophthalmoplegia has been reported after excessive dosing. The injections have been associated with a burning sensation which lasts for 1-2 min after injection. Allergic reactions eg, skin rashes and influenza-like symptoms have occasionally been noted.