QT prolongation after accidental tamoxifen ingestion in a 5-year-old child

Objective: Five percent of all hospital admissions in Europe are caused by adverse drug reactions (ADRs) which are the fifth cause of death in hospital.[1] Therapeutic errors account for 18.7–56% of all ADRs.[2] Tamoxifen is a nonsteroidal antiestrogen that antagonizes estrogen receptors in breast cancer cells thereby preventing their growth.[3] Although tamoxifen overdose is extremely rare, neurotoxicity and prolonged QT interval are described as side effects and the drug is not labeled for pediatric use. Case report: Tamoxifen citrate (20mg) was accidentally administered to a 5-year-old child instead of a leukotriene receptor antagonist used for the maintenance treatment of asthma. After consulting the Poison Center of Florence Careggi University Hospital, the child was admitted to the Emergency Room of Siena Hospital. On arrival, electrocardiogram (ECG) was performed and activated charcoal was administered. Intravenous fluid therapy with saline was started and considering tamoxifen’s long half-life (5–7 days), continuous ECG recording was performed. QTc prolongation was observed 9 and 47 hours after ingestion (0.47 s and 0.46 s, respectively). No other symptoms were reported. The child remained in hospital for five days and was discharged after QTc normalization. Conclusion: In this case, a single dose of tamoxifen caused the development of QTc prolongation in a pediatric patient. Unintentional therapeutic errors are frequent and can cause severe ADRs and patient hospitalization. The American Association of Poison Control Centers reported that medication errors continue to be a source of preventable injury with increasing incidence across the out-of-hospital population.[4] In 2014, the Poison Center of Florence received 4331 calls and 188 (4.3%) were related to therapeutic errors. Safe and appropriate drug use, risk reduction and error prevention must be promoted.