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Serum tobramycin levels in low- and very low-birthweight infants
Insights
High tobramycin sulfate trough levels were observed in premature infants during the first week of therapy. Monitoring serum concentrations and adjusting dosage is recommended to maintain safe levels below 2 mcg/ml.
Area of Science:
- Neonatal pharmacokinetics
- Pediatric pharmacology
- Antibiotic drug monitoring
Background:
- Premature infants have unique physiological characteristics affecting drug metabolism.
- Tobramycin is an aminoglycoside antibiotic commonly used in neonatal infections.
- Establishing safe and effective dosing regimens for neonates is crucial.
Purpose of the Study:
- To evaluate serum tobramycin sulfate concentrations in premature infants.
- To assess the impact of age and birth weight on tobramycin levels.
- To determine the safety of tobramycin therapy in this population.
Main Methods:
- Intravenous infusion of tobramycin sulfate at 2.5 mg/kg in 43 premature infants.
- Serum tobramycin levels measured by enzymatic immunoassay (EMIT) on days 1, 3, and 5.
- Infants categorized by birth weight: ≤1500 gm and 1501–2500 gm.
Main Results:
- Peak serum tobramycin levels increased from day 1 to day 3 and plateaued by day 5.
- Trough levels exceeded 2 mcg/ml in approximately 40% on day 1 and over 70% on days 3 and 5.
- No renal toxicity or auditory dysfunction was detected.
Conclusions:
- Premature infants exhibit high tobramycin trough levels in the first week of life.
- Therapeutic drug monitoring of tobramycin is advisable in neonates.
- Dosage adjustments or extended dosing intervals may be necessary to maintain trough levels below 2 mcg/ml.
Abstract:
This study was designed to evaluate the serum concentration of tobramycin sulfate following a 2.5-mg/kg intravenous infusion in 43 premature infants on days 1, 3, and 5 of age (therapy). Twenty premature infants weighing 1500 gm or less at birth and 23 others whose birthweights ranged from 1501 to 2500 gm made up the study population. Serum tobramycin levels were measured by an enzymatic immunoassay (EMIT) at one, four to six, and 12 hours after injection. Peak serum levels increased from day 1 (means, 5.2 +/- 2.2 mcg/ml) to day 3 (means, 6.1 +/- 2.6 mg/ml) and then remained unchanged at day 5 (means, 6.1 +/- 2.4 mg/ml). Approximately 40% of the study population presented trough levels above 2 mcg/ml on day 1 and over 70% on days 3 and 5. No evidence of renal toxicity or auditory dysfunction was observed. In light of the high trough levels observed during the first week of life in premature infants, it may be judicious to monitor serum tobramycin concentration and to decrease the dosage or to prolong the dose interval in order to maintain trough concentrations below 2 mcg/ml.