Serious Adverse Events Associated with Off-Label Use of Azithromycin or Fentanyl in Children in Intensive Care Units: A Retrospective Chart Review.

Half of prescription drugs commonly given to children lack product labeling on pediatric safety, efficacy, and dosing. Two drugs most widely used off-label in pediatrics are azithromycin and fentanyl. We sought to determine the risk of serious adverse events (SAEs) when oral azithromycin or intravenous/intramuscular fentanyl are used off-label compared to on-label in pediatric intensive care units (ICUs). Six pediatric hospitals participated in a retrospective chart review of patients administered oral azithromycin (n = 241) or intravenous/intramuscular fentanyl (n = 367) between January 5, 2013 and December 26, 2014. Outcomes were SAEs by drug and labeling status: off-label compared to on-label by Food and Drug Administration (FDA)-approved age and/or indication. Statistical analysis was performed using logistic regression to estimate odds ratios (ORs) and Cox regression to estimate hazard ratios (HRs). Twenty-one (9%) children receiving azithromycin experienced SAEs. Off-label use of azithromycin was not associated with a higher risk of SAE (OR 0.87, 95% CI 0.27-2.71, p = 0.81). Ninety-five (26%) children receiving fentanyl experienced SAEs. Fentanyl off-label use by both age and indication was not associated with a higher risk of overall SAEs compared to on-label use (OR 1.99, 95% CI 0.94-4.19, p = 0.07). However, the risk of the SAE respiratory depression was significantly greater when fentanyl was used off-label by both age and indication (OR 5.05, 95% CI 1.08-23.56, p = 0.044). Results based on HRs were similar. Azithromycin off-label use in pediatric ICUs does not appear to be associated with an increased risk of SAEs. Off-label use of fentanyl appears to be more frequently associated with respiratory depression when used off-label by both age and indication in pediatric ICUs. Prospective studies should be undertaken to assess the safety and efficacy of fentanyl in the pediatric population so that data can be added to the FDA labeling.