When used therapeutically, botulinum toxin (BT) has to be injected into its target tissues. All manufacturers warn not to do so in patients with oral anticoagulation to avoid haematoma. We wanted to study the haematoma frequency (HF) in patients with anticoagulation receiving BT therapy. 32 patients (16 females, 16 males, age 69.3 ± 10.0 years) with blepharospasm (n = 6), hemifacial spasm (n = 8), post-stroke spasticity (n = 16), and cervical dystonia (n = 2) received BT therapy (needle size 27G, post-injection tissue compression) whilst on anticoagulation (anticoagulation group, AG). 32 patients matched for disease, target muscles, age, and gender received identical BT therapy without anticoagulation (control group, CG). Anticoagulation was performed with phenprocoumon. International normalised ratio (INR) at the time of BT injection was in all patients within the recommended margins of 2.0 and 3.0 (mean 2.6 ± 0.27). Overall HF was 3.0% in AG and 1.8% in CG (not significant). All hematomas occurred in blepharospasm patients (AG 5.2%, CG 2.6%, not significant) and hemifacial spasm patients (AG 3.9%, CG 2.9%, not significant). In cervical dystonia and spasticity there were no haematomas. Throughout an observation period of 4 years, none of the haematomas was surgically relevant. Haematomas are a rare complication of BT therapy, mainly occurring in periocular injections. Anticoagulation only marginally increases HF, provided INR is controlled and appropriate injection techniques are used. Surgically relevant haematomas do not occur. Interruption of oral anticoagulation to perform BT therapy is not justified.
Keywords: Adverse effects; Anticoagulation; Botulinum toxin; Drug safety; Haematoma.