Tobramycin Level Peak

1. Pharmokinetic factors including dosage form, mode of administration, and concomitant drug therapy can influence appropriate time of specimen collection following administration of tobramycin.

2. For patients receiving tobramycin via conventional dosing methods peak and trough, drug monitoring should begin after a steady state is achieved (usually after 3-4 doses). Specimens for peak concentrations should be collected 60 to 90 minutes after intravenous infusion. Specimens for trough concentrations should be collected within 30 minutes of next dose.

3. For patients receiving trobramycin via pulse-dosing method, monitoring can begin after the first dose because steady-state conditions are not obtained. Monitoring strategies will vary with dosing regimens. When using pulse dosing nomograms, a timed specimen should be collected 8 to 12 hours after completion of drug infusion in order to determine subsequent dosing interval. This should be repeated at 3 to 7 day intervals or more frequently as warranted.

4. Concentrations of  beta-lactam antibiotics (penicillins and cephalosporins) at therapeutic levels may inactivate tobramycin in vivo and in vitro. Specimens from patients receiving beta-lactam antibiotics (penicillins and cephalosporins) must be analyzed immediately upon receipt or stored frozen to prevent in vitro inactivation of tobramycin