Background and aims Intramuscular injection is contra-indicated in patients with bleeding disorders. In these cases, the unlicensed practice is to administer vaccines by subcutaneous route. Despite extensive literature search and communication with the manufacturer, we were unable to retrieve any reported experience with palivizumab. Supported by a mathematical description (Zhao L et al. J Clin Pharmacol 2013) for subcutaneous or intramuscular administration of monoclonal antibodies, we decided to administer pavilizumab by subcutaneous route and to document the effects. Parental informed consent was obtained.

Methods Prospective registration of tolerance and effects of subcutaneous palivizumab administration in a former preterm girl with von Willebrand, type 2B. Spare plasma samples (peak and through levels) were also collected, but analysis was not possible since we had no access to a valid quantification technique.

Results The girl received 5 monthly subcutaneous injections (15 mg/kg) and was subsequently monitored for 1 h for systemic and local side effects with further evaluation of tolerance by the parents. Local tolerance of palivizumab (tenderness, swelling) was much better when compared to the simultaneously administered (Infarix Hexa, or Prevenar subcutaneous) vaccines. She never displayed RSV-related symptoms.

Conclusions Repeated subcutaneous injection of palivizumab was tolerated well with minor local reactions and no systemic side effects. We suggest to consider the subcutaneous instead of the intramuscular route in the setting of a valid indication for palivizumab, but an contraindication for intramuscular administration. Off-label or unlicensed practices should be reported to share and improve knowledge on pharmacotherapy.