Serum standards for the bioassay of aminoglycosides in cerebrospinal fluid

Four diluents were compared as reference standards for the assay of gentamicin in cerebrospinal fluid (CSF): human CSF, human serum, distilled water, and 150 mmol NaCl/4.5 mmol CaCl2. Standards prepared in pooled human serum were the best alternative to CSF for the assay of gentamicin and were also useful for the assay of tobramycin, netilmicin, amikacin, and sisomicin. The pH (6.0-9.8) of CSF did not alter the results of the assay.