Background Daptomycin is a concentration dependent antibiotic with particular sensitivity to strains of Staphylococcus aureus. Its novel mechanism of disrupting cell membranes makes it particularly useful for treating bacteraemias caused by strains showing resistance to more conventional therapies. Since daptomycin became available in 2006, guidance on off-label dosing in paediatrics has been fairly limited. However recent pharmacokinetic studies have shown that the peak levels achieved varies significantly with age.1–,4 These data show that extrapolation of the adult dose of 4–6 mg/kg to children will usually give sub-therapeutic levels.
Aim To identify the current prescribing of daptomycin and what doses have been used and to evaluate if these prescriptions follow the most up to date evidence based publications.
Methods A retrospective audit was conducted to assess prescriptions for daptomycin in the Newcastle Upon Tyne Hospitals NHS FT. A 12-month period was investigated between June 2011 to July 2012.
Patients who received a course of daptomycin were identified using JAC dispensing records from our aseptic unit which dispenses daptomycin as part of our CIVAS range. Relevant patient information was collected from clinical notes (e.g. PICU discharge, operative notes etc.) available by our electronic records system.
The doses prescribed were then calculated as mg/kg. Medical notes were not reviewed for any patients because every CIVAS order is checked by a clinical pharmacist and so they are assumed appropriate for each individual case for the condition requiring treated.
Results There were 9 patients identified in total who had received a course of daptomycin over the 12 month period. The patients were spread over a variety of wards including PICU, PCICU and a BMT ward. The mean age was 36 months and median dose was 5.4 mg/kg. 55% of doses were prescribed at a dose of 4 mg/kg.
Conclusion This audit showed that there was widespread use of the adult dosing regime with over half of patients receiving a dose of 4 mg/kg once daily. The current evidence shows that like other renally excreted antibiotics such as ertapenem, that daptomycin undergoes enhanced renal clearance in children compared to adults on a mg/kg basis.4 This suggests that some patients are being under treated and may be at greater risk of treatment failure.
One barrier identified to standardise prescribing is the lack of information on daptomycin contained within commonly used references (e.g. cBNF). As a result of the audit, a new guideline was written to summarise the available evidence and guide prescribers. The document has been approved by the Trust Antimicrobial Steering Group in December 2012 and the plan is to re-audit 1 year after guideline implementation to assess the impact of this new guideline.