Summary
Nineteen newborn infants receiving tobramycin, 2.5 mg/kg every 12 h were studied on two occasions at steady-state during the first week of postnatal age. The two studies were separated by two to four days. Total body clearance of tobramycin averaged 1.15 and 1.14 ml/min/kg (p>0.05), apparent volume of distribution averaged 0.82 and 0.68 l/kg (p>0.05), and elimination half-life averaged 8.6 and 7.1 h (p>0.05), during the first and second study, respectively. When the data were further analyzed based on the birth weight, tobramycin kinetics changed during the second study compared to the first study in very low birth weight infants. In eight infants ⩽1.5 kg birth weight, although total clearance of tobramycin was similar, the average apparent volume of distribution decreased from 1.04 l/kg during the first study to 0.73 l/kg during the second study (p<0.05) and elimination half-life from 11.1 h during the first study to 8.7 h during the second study (p<0.05). These data indicate that these infants may require a change in dosing interval with continued tobramycin therapy during the first week of postnatal age. Intrapatient variation in tobramycin kinetics should be considered, in addition to the interpatient variation reported previously, when monitoring the serum concentration to individualize tobramycin therapy in newborn infants ⩽1.5 kg birth weight.
References
Arant BS (1982) Fluid therapy in the neonate — concepts in transition. J Pediatr 101: 387–389
Williams V, Shirkey HC (1976) Pediatric clinical pharmacology and therapeutics. In: Avery GS (ed) Drug treatment. ADIS Press, Publishing Sciences Group, Acton, MA, USA, pp 71–122
Bell EF, Oh W (1978) Fluid and electrolyte balance in low birth weight infants. Clin Perinatol 6: 139–146
Dahlgren JG, Anderson ET, Hewitt WL (1975) Gentamicin blood levels: a guide to nephrotoxicity. Antimicrob Agents Chemother 8: 58–62
Lorenz JM, Kleinman LI, Kotagal VR, Reller MD (1983) Water balance in very low-birth-weight infants: relationship to water and sodium intake and effect on outcome. J Pediatr 101: 423–432
Nahata MC, Powell DA, Gregoire RP, McClead RE, Menke JA, Bickers RG, Glazer JP (1983) Tobramycin kinetics in newborn infants. J Pediatr 103: 136–139
Physician's desk reference (1983) 37th edn. Medical Economics, Oradell, NJ, USA, pp 900–902
Author information
Authors and Affiliations
Additional information
supported by Lilly Research Laboratories, Indianapolis, USA
Rights and permissions
About this article
Cite this article
Nahata, M.C., Powell, D.A., Durrell, D.E. et al. Intrapatient variation in tobramycin kinetics in low birth weight infants during first postnatal week. Eur J Clin Pharmacol 26, 647–649 (1984). https://doi.org/10.1007/BF00543504
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00543504