Audit of Safety of Intramuscular Botulinum Toxin Injections among Patients Receiving Warfarin Anticoagulation Therapy

Abstract

Abstract Background Botulinum toxin (BTX) intramuscular injections are an effective treatment for spasticity in acquired brain injury. Despite use since the 1980s, issues concerning technique, dose and long-term side-effects remain unresolved. For example, the safety of BTX in warfarinised patients is unclear. There are two studies reporting the risk of intramuscular injections in patients receiving anticoagulant therapy with regard to possible local haematoma formation. There is no advice on this subject in the manufacturers’ summary of product characteristics for the original brand of warfarin, Dysport, BOTOX, Xeomin or in the British National Formulary. Aim To assess the safety of BTX injections in patients receiving oral anticoagulation. Design Prospective audit of safe practice. Setting Outpatient setting in a rehabilitation centre. Population Adult population affected with spasticity with acquired brain injury and receiving concurrent warfarin anticoagulant therapy. Methods Fourteen patients who were receiving anticoagulant therapy were given regular BTX (number of injection cycles or total mean no of injections each). Patients gave written informed consent before the injections. Injection technique did not differ from that used for un-anticoagulated patients. Patients were assessed by the injector for obvious haemorrhage in the first 15 minutes after the injection resulting in swelling, bruising, tenderness or haematoma. Patients were asked to watch for appearance of local reactions like swelling, bruising or haematoma and pain in the first week. Results There were no clinically detectable local complications after intramuscular injections and no major or minor bleeding episodes after BTX injections. Conclusion In our group, BTX injections were administered intramuscularly to patients who were receiving anticoagulant therapy without significant risk of local bleeding. However, injections must be used with caution in patients with an INR above the therapeutic range. Clinical rehabilitation impact BTX can be safely given in patients on anticoagulation therapy with safety checks in place.