Rhabdomyolysis Reported for Children and Adolescents Treated with Antipsychotic Medicines: A Case Series Analysis

OBJECTIVE: Rhabdomyolysis is a rare and potentially serious adverse drug reaction (ADR) to antipsychotic medicines. The aim of this study was to investigate the clinical circumstances surrounding the diagnosis of rhabdomyolysis in children and adolescents treated with antipsychotic medicines. We also critically reviewed individual case safety reports (ICSRs) of suspected ADRs to evaluate how clinically useful they can be in a case series analysis. METHODS: This was a descriptive and an exploratory study. Published case reports and ICSRs from the World Health Organization (WHO) Global ICSR database, VigiBase, reported with rhabdomyolysis and antipsychotic medicines for patients ≤17 years years of age were described. Reporting patterns of ICSRs with rhabdomyolysis and antipsychotic medicines were explored in VigiBase for children and adolescents and for adults. The VigiBase ICSRs were also systematically evaluated regarding the report content. RESULTS: Of the 26 evaluated reports, 6 co-reported neuroleptic malignant syndrome (NMS) and 20 reports concerned rhabdomyolysis in the absence of NMS. The reported suspected antipsychotic medicines for these 20 reports were olanzapine, risperidone, haloperidol, paliperidone, quetiapine, clozapine, cyamemazine, and aripiprazole. In VigiBase, rhabdomyolysis (in the absence of NMS) was reported more frequently with olanzapine relative to all reports for children and adolescents with antipsychotic medicines. In the range of events that preceded rhabdomyolysis, muscle pains and abdominal pain were commonly recorded to have started during the week prior to the diagnosis. Other preceding symptoms were general weakness and dark urine. Onset of rhabdomyolysis for most patients occurred at any time within 2 months of starting antipsychotic treatment, in several cases triggered by changes to the patient's drug therapy or known risk factors of rhabdomyolysis. It was found that ICSRs can contribute with additional information, but that access to free text and narratives were crucial in order to capture clinically useful features of rhabdomyolysis. CONCLUSION: Monitoring of children and adolescents needs to be intensified during dose increases, or when a new, added, or switched antipsychotic medicine is introduced to their drug regimen, and during exposure to known risk factors for rhabdomyolysis. The development of seemingly nonserious events, such as abdominal pain, muscle pain, weakness, and dark urine, should be followed up during antipsychotic use, as they might be precursory events to rhabdomyolysis that eventually could develop into acute renal failure.