Recently, the safety of APs has been questioned, as both hypersensitivity reactions and renal impairment have been reported to be higher than 10%. Premature discontinuation of APs attributed to adverse events occurred in >20% of patients treated with high dosing of oxacillin (12g/day) for complicated MSSA bacteremia. This might be linked to the growing number of cumulative comorbid conditions and to ageing. In particular, administration and dosing schedule for APs are not well defined in patients with chronic kidney disease with decreased rate of glomerular filtration. Today, data are missing for renal adjustment.