Pharmacokinetic and nephrotoxic study of gentamicin in rabbits using a new dosage regimen

Currently, in certain clinical situations there is an increasing trend towards using dosage regimens involving aminoglycoside antibiotics based on the administration of a single dose of the drug per day instead of administering the same amount in two or three administrations. The aim of the present study was to discover the pharmacokinetic profile and the nephrotoxic potential of this new form of administration in experimental animals receiving gentamicin. The study was conducted on two groups of rabbits, one of which received a single dose of the drug at 7 mg/kg i.v. and the other 7 mg/kg administered every 12 hours, allometrically equivalent to gentamicin dosing at 5 mg/kg every 24 hours to human subjects. The number of doses administered was 20. From the pharmacokinetic point of view, the results point to the existence of a significant degree of accumulation of the antibiotic in renal cortex as a result of the dosage regimen, no important modifications occurring in the pharmacokinetic parameters of gentamicin calculated from its plasma kinetics. This shows that the two compartment model employed predicts drug levels in accessible tissues but not in deep ones where gentamicin is accumulated for long periods of time. From the toxicological point of view, the treatment caused appreciable damage of the renal tubules during the first phases of the treatment which was not detectable from the serum creatinine levels or the kinetic behaviour of the aminoglycoside.