Gentamicin elimination glomerular filtration

Age-related alteration of renal function is a very important factor in selecting the dose regimen. Renal function in newborns is incompletely developed. Neonatal renal plasma flow and glomerular filtration rates (normalized for body surface) are only 30-40% of those of adults. The half-life of penicillin G is 3.2 h in newborns (up to 6 days of age) and 1.4 h in infants (14 days of age or older), whereas in older children and adults, it is about 0.5 h. The mean half-life of gentamicin is about 5h in newborns under 1 week of age and about 3 h in infants 1-4 weeks of age. The half-life of gentamicin in older infants and adults is approximately 2 h. Thus, drugs that depend on renal excretion as the principal mode of elimination would be expected to have a longer residence time in infants. 

Species variations in the half-life of drugs that are eliminated by renal excretion is less pronounced than for lipid-soluble drugs that undergo extensive hepatic biotransformation. The half-life of gentamicin, which is eliminated solely by glomerular filtration, is 0.5-1 h in laboratory animals, 1.25-2.5 h in domestic animals. 

Aminoglycosides are almost exclusively eliminated by glomerular filtration. Elimination is dependent on cardiovascular and renal function, age, fever, other physiological factors and the V. The half-lives are usuaUy 1-2 h in normal adult horses but are increased in horses with renal dysfunction and in neonates. Increased dosage intervals must be used in these patients to prevent nephrotoxicity. The renal elimination of the aminoglycosides increases with age. The half-life of gentamicin is approximately 50% longer in 1-day-old than in 30-day-old foals. 

Following parenteral administration, the distribution of gentamicin is virtually restricted to extracellular fluid, and elimination takes place solely by glomerular filtration. The pattern of age-related changes in the disposition of gentamicin is similar in foals (Cummings et al.r 1990) and in calves (Clarke et al.r 1985). Values of the systemic clearance of gentamicin in 1- and 5-day-old foals and calves compared with mares and cows, respectively, indicate that... 

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