Postconceptional age and gentamicin elimination half-life.

We examined the correlation between the elimination half-life of gentamicin and postnatal or postconceptional age in 104 infants greater than 24 weeks to less than or equal to 48 weeks postconceptional age. A weak correlation was observed between half-life and postnatal age (R = -0.353). A better correlation existed between postconceptional age and half-life (R = -0.572). A plot of the log of the mean half-life against postconceptional age was virtually linear. We conclude that postconceptional age is a major determinant of an infant's ability to excrete gentamicin, and speculate that the relationship between half-life and decreasing postconceptional age is exponential.