A review of tobramycin levels in paediatric cystic fibrosis patients

Introduction Cystic fibrosis is a common recessive disorder primarily affecting the lungs and often resulting in pulmonary infection by Pseudomonas aeruginosa. Tobramycin is currently used to prevent the growth of Pseudomonas aeruginosa; however, it has a narrow therapeutic index and requires extensive monitoring. The aim of this study was to review the current practice in administration and monitoring of once daily tobramycin in paediatric cystic fibrosis patients at Birmingham Children’s Hospital (BCH).
Materials & Methods Design: Analysis of forty-nine once daily tobramycin courses in fifteen patients (five male; ten female) during 2010. Setting: Birmingham Children’s Hospital, UK. Main outcome measures: Patient height and weight, dosage and time of administration, drug plasma levels, urea and electrolyte levels.
Results: Once daily tobramycin was administered at a mean dose of 9.94 mg/kg (n = 49, range 8.8–11.0 mg/kg) which is consistent with current BCH guidelines. At least one trough level was observed for every course (mean = 1.33; n = 49). Trough levels greater than 1 mg/L were found in 17% (n = 11/65) of samples. Tobramycin was administered between 15:00 and 21:00 in 75% (n = 30/40) of courses, with a further 23% (n = 9/40) of courses being administered after 21:00. Only 39% (n = 19/49) of courses had urea and electrolyte levels monitored conflicting with current practice elsewhere in the UK. Furthermore, no patients underwent any routine monitoring for ototoxicity.
Discussions, Conclusion: The use and associated monitoring of once daily tobramycin varies within the UK. Current practice at BCH with regard to the dosing of once daily tobramycin and the timing of the first trough level are consistent with available guidelines. However an increase in the frequency of renal monitoring is recommended considering national practice as urea and creatinine levels should be taken at least once within a fourteen day course. Furthermore, a proportion of courses were administered after 21:00 which, due to a decrease in glomerular filtration rate, may result in an increased risk of toxic effects.
Disclosure of Interest: None Declared