Gentamicin drug level for IP gentamicin is not mandatory. There are good dosage guidelines for gentamicin administration in the ISPD peritonitis guideline 2000 and 2005. RRF may affect the trough drug level. As now most use intermittent daily gentamicin, which based on the ‘post-antibiotic’ effect of high concentration IP aminoglycosides, checking the peak serum gentamicin is not helpful. But one may have to make sure that the serum trough level is low enough to avoid drug toxicity, particularly with prolonged gentamicin administration (e.g., >2 week).