Homework SourseA 7 yo patient with pyelonephritis is started on gentamicin
A 7 yo patient with pyelonephritis is started on gentamicin 9.5 mg/kg/dose IV every 24 hours. Using the above guidelines, you calculate a Cmax of 9.2 mcg/ml and half life of 3.87 hr^-1 What changes in the dosing regimen, if any, will you make?
Solution
The Cmax is the peak serum concentration achieved by a drug after administration. For gentamicin therapy, Cmax is a critical pharmacokinetic value. For acute infection, the Cmax should be > 10mcg/ml. The ideal Cmax should be (12-21) mcg/ml.
The given patient is on an extended interval weight dependent dosing, of 24 hours. Gentamicin has toxic effects for the kidneys since the drug is cleared by the renal system. In the patient suffering from pyelonephritis, a kidney infection, the dosage of the drug should not be too high.
Yet, according to the guidelines, if the Cmax is to be increased, then the dose will have to be increased using the following expression:
Original dose x (New Cmax/Original Cmax)
