Cephalothin plus an aminoglycoside is more nephrotoxic than methicillin plus an aminoglycoside.

In a prospective, randomised, double-blind trial to determine if cephalothin plus an aminoglycoside is more nephrotoxic than methicillin plus an aminoglycoside, patients were assigned to one of four treatment groups: cephalothin and gentamicin (C.G.), cephalothin and tobramycin (C.T.), methicillin and gentamicin (M.G.), or methicillin and tobramycin (M.T.). The incidence of definite nephrotoxicity was: C.G., 7/23 (30.4%); C.T., 5/24 (20.8%); M.G., 2/20 (10%); and M.T., 1/23 (4.3%). There was no statistically significant difference in nephrotoxicity between the combined gentamicin groups (C.G. and M.G.) and the combined tobramycin groups (C.T. and M.T.). Definite nephrotoxicity developed in 12/47 (25.5%) of the combined cephalothin groups (C.G. and C.T.) and in only 3/43 (7%) of the combined methicilllin groups (M.G. and M.T.). The combination of cephalothin plus an aminoglycoside is therefore more nephrotoxic than the combination of methicillin plus an aminoglycoside.