Serum Tobramycin Concentrations Research Articles

Single daily doses of tobramycin in therapy of urinary tract infections.

Results of therapy with tobramycin for infections caused by susceptible pathogens have been impressive. The usual multiple dose regimen is aimed at maintenance of the serum concentration of tobramycin above the minimal inhibitory concentration of the causative pathogen throughout the course of therapy. Evidence is accumulating, however, that the urinary concentration of antibiotics may be of greater importance than the serum concentration in the treatment of urinary tract infections. This concept has been supported by results of studies with nitrofurantoin, naladixic acid, tetracycline, and, more recently, gentamicin. The present study of 90 patients with urinary tract infections treated with a single intramuscular daily dose of tobramycin resulted in round-the-clock urinary levels of tobramycin that exceeded the minimal inhibitory concentration of the offending pathogen. The clinical and bacteriologic response to therapy was excellent, and no oto- or nephrotoxicity occurred. This regimen frequently allows for therapy on an outpatient basis, fewer painful injections for the patient, and the saving of nursing time and expensive supplies.

Commentary: An appraisal of tobramycin usage in pediatrics

Tobramycin is a newly marketed aminoglycoside which closely resembles gentamicin in antimicrobial activity, pharmacology, clinical efficacy, and toxicity. It is somewhat more active in vitro against Pseudomonas aeruginosa than is gentamicin and may have a lower ototoxic potential. Tobramycin should be considered a limited-purpose drug for pediatric patients until greater clinical experience has been gained. At the present time the major indication for its use is for treatment of infections caused by coliforms or pseudomonas resistant to kanamycin and gentamicin. Demonstration of in vitro susceptibility is mandatory because resistance to tobramycin and the other aminoglycosides may be mediated by the same episome (R-factor). The recommended dosage is 2 mg/kg every 12 hours (4 mg/kg/day) intramuscularly or as a two-hour intravenous infusion to neonates, with the possible exception of full-term infants over seven days of age who may require administration every eight hours. Beyond the neonatal period, the dosage should be 1.0 to 1.5 mg/kg every eight hours (3 to 4.5 mg/kg/day). Larger dosages may be required for treatment of meningitis, but presently there is no information on which to base a recommendation. Neither is there experience with intrathecal use in infants. It is desirable to monitor tobramycin serum concentration to be certain that peak values are within the therapeutic range of 3 to 8 mug/ml. Dosage must be reduced in patients with impaired renal function and monitoring of serum concentrations is imperative. All patients should be evaluated for evidence of renal and eighth nerve toxicity.