Murphy and Roether reported 2 nomograms for dosing gentamicin in neonates at extended intervals. One nomogram has a lower target gentamicin trough than the other nomogram. The authors are from the University of Arizona and United Drugs in Tuscon.
Dose of gentamin: 4 mg per kg weight at birth
Target gentamicin trough: <= 0.5 mg/L at 22 hours
Preferred time for blood sample collection: 15 to 21 hours after previous dose (allowed range 13 to 22 hours)
Parameters:
(1) birthweight in kilograms
(2) number of hours since previous gentamicin infusion
(3) serum gentamicin concentration in mg/L
Line |
Formula for Serum Gentamicin Concentration |
A |
(0.00796 * ((hours)^2)) - (0.4063 * (hours)) + 5.618 |
B |
(0.0072 * ((hours)^2)) - (0.4240 * (hours)) + 7.257 |
C |
(0.004167 * ((hours)^2)) - (0.3343 * (hours)) + 7.550 |
Serum Level at Sampling Time |
Dosing Instruction |
<= A |
every 24 hours |
> A but <= B |
every 36 hours |
> B but <= C |
every 48 hours |
> C |
repeat blood level |
where:
• If the serum level is > C, then a repeat blood level is performed at 48 hours. If trough level exceeds the target concentration at that time then withhold the next dose for a longer interval. Further doses should be administered cautiously.
Specialty: Infectious Diseases, Pharmacology, clinical