Ivabradine poisoning: a retrospective observational case series

Introduction Ivabradine is an anti-arrhythmic drug that targets the cardiac pacemaker funny current (If). It is used in the management of patients with uncontrolled angina, heart failure and postural orthostatic tachycardia syndrome. There is limited research describing ivabradine poisoning. We aimed to characterise ivabradine toxicity following deliberate overdose.Methods This is a retrospective observational case series of patients with acute deliberate ivabradine poisoning referred to a state Poisons Information Centre and three Australian tertiary toxicology units between 1 July 2017 to 31 July 2024.Results There were 24 presentations over the 7-year period. Sixteen cases were female, and median age was 24 years (range: 18–82 years). The most common indication for ivabradine was postural orthostatic tachycardia syndrome (13/17). The median dose ingested was 126.25 mg (range 22.5–420 mg). Co-ingestion occurred in 20 presentations (20/24). Bradycardia occurred in 13 cases (13/24) with a median dose of 200 mg (range 30–420 mg). The median lowest heart rate recorded was 45 bpm (range: 20–66 bpm). There was no association between ingested ivabradine dose and heart rate (Pearson’s R2 = 0.15). Four patients had hypotension, and three received catecholamines. All four had co-ingestants. One patient who co-ingested 5000 mg of metoprolol received cardiac pacing. The main driver of severe hypotension was attributed to co-ingested agents in all presentations. The median hospital length of stay was 19 h (interquartile range 13–50 h).Conclusions Ivabradine commonly causes bradycardia in overdose. Severe toxicity occurred infrequently and only with co-ingestions. Toxicity did not appear to be dose dependent.