No hearing loss after repeated courses of tobramycin in cystic fibrosis patients

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Renske J. Scheenstra*ac, Harry G.M. Heijermanbc, Charlotte L. Zuurec, Daan J. Touwec & Evert Rijntjesdca Department of Otorhinolaryngology, Head and Neck Surgery, The Netherlands Cancer Institute, Amsterdamb Adult Cystic Fibrosis Centre, Department of Pulmonologyc Department of Clinical Pharmacologyd Department of Otorhinolaryngology, Head and Neck Surgery, Haga Teaching Hospital, The Haguee Department of Otorhinolaryngology, Head and Neck Surgery, VU University Medical Centre, Amsterdam, The NetherlandsCorrespondence: R.J. Scheenstra, Department of Otorhinolaryngology, Head and Neck Surgery, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. 020-5122550. r.scheenstra@nki.nl*Present address: Department of Otorhinolaryngology, Academic Medical Centre, Amsterdam, The Netherlands.Conclusion: Our results indicate that repeated treatment courses with tobramycin 10 mg/kg (twice daily for 3 weeks) may be safely applied in cystic fibrosis (CF) patients with respect to ototoxicity. The risk of hearing loss in this patient group is less than expected, which could be explained by either unfavourable baseline audiometry or the use of unidentified protective medication, or both. However, due to large inter-individual variations, audiometry screening remains important with respect to the detection of individual outliers. Objectives: Tobramycin is frequently prescribed for CF patients. In this study, hearing loss due to cumulative tobramycin exposure in adult CF patients was investigated. Patients and methods: We retrospectively investigated 19 patients with both baseline and follow-up audiometry before and after repeated courses of intravenous tobramycin (10 mg/kg/day in twice daily administrations for 3 weeks). Pure tone audiometry was performed at 0.250–16 kHz. Results: After repeated courses of tobramycin (median 3, range 1–8), the mean increase per frequency was 2.1 dB (median 0.5 dB, SD 12.6) with large (inter-individual) variations (range –23.5 to 34.5 dB). The pure tone averages (PTA) at 1-2-4 kHz and 8-10-12 kHz increased 1.4 dBHL and 2.3 dBHL, respectively, but were neither statistically significant, nor correlated with the cumulative tobramycin exposure.