Ototoxicity of amikacin on newborn infants

Abstract

Objective To study the ototoxicity of routine dose amikacin in newborn infants and the relationship with amikacin blood concentration and to provide a possible rule for safely using amikacin in neonates. Methods Brainstem auditory evoked potential (BAEP) was carried out to monitor auditory function in amikacin [10 mg/ (kg·d) × 7 days] treated group (26 cases) and control group (20 cases) of newborn infants before and after treatments. Blood amikacin concentrations were measured in amikacin treated group by fluorescence polarization immunoassay. Results BAEP monitoring showed abnormal in 3 cases (12%) in amikacin treated group, while no abnormal case was found in the control group at the 7 th day of the study course. The difference was not significant (P > 0.05) . Two abnormal cases recovered, and one missed during follow-up observation. If the missed case was still abnormal, the abnormality rates of amikacin treated group could be 4%. And there was still no statistical difference between two groups after follow-up ( P > 0.05) . Threshold V (THR V ) was (38 ± 8) dBnHL in amikacin treated group and (34 ± 11) dBnHL in control group after treatments. There was no statistical difference between them (P > 0.05) . THR V in amikacin treated group after treatment did not increase significantly comparing to the baseline (P > 0.05) . Three cases with abnormal BAEP presented prolonged peak latency I (PL I ) . After the treatment, PL I which reflects the peripheral function of the hearing conduction route was (1.60 ± 0.24) ms in amikacin treated group, which was significantly higher than that in control (1.48 ±0.12) ms and the baseline (1.53 ± 0.14) ms, respectively (P 0.05) . The amikacin peak concentration was (17 ± 3) mg/L in 10 cases at the 3 rd day and (16 ± 3) mg/L in 18 cases at the 7 th day of the treatment. Blood peak concentrations were all lower than 35 mg/L, and blood trough concentrations were all lower than 5 mg/L (0 ~1.51 mg/L) . Conclusion The intravenous administration of amikacin with a dosage of 10 mg/kg once a day may reach the efficient blood concentration in most term neonates, and the peak and the trough blood concentrations were within the safe range. The 7 day course of amikacin in the dose of 10 mg/kg once a day does not cause clinical ototoxicity in term neonates, but it may result. in reversible mild peripheral hearing dysfunction. It is necessary to monitor ototoxicity with BAEP when the treatment exceeds 7 days. Key words: Amikacin; Ear; Toxicology; Infant, newborn; Evoked potentials, auditory, brain stem; Blood