Abstract
The use of amikacin (AMK) in newborns was investigated and the results obtained are summarized as follows.
1. AMK was administered to 3 rabbits at an intramuscular dose of 6 mg/kg. Mean blood levels determined according to methods of bipassay (BIO) and fluorescent immunoassay (FIA) were 28.6 and 22.2 μg/ml, respectively, at 30 minutes after dosing. Then, the blood levels declined rapidly. Mean T 1/2 values obtained with the above 2 assay methods were 0.76 and 0.63 hours, respectively.
2. When AMK was administered at a dose of 5.7 mg/kg to a 64 day-old newborn by drip intravenous infusion for 30 minutes, a peak blood level was attained at the end of drip intravenous infusion, which was 20.0 μg/ml according to BIO and was 15.5 μg/ml according to FIA. The blood levels declined gradually thereafter with a T 1/2 value of 2.33 hours (BIO) or 2.03 hours (FIA). When the drug was administered at 5.3 mg/kg to a 26 day-old newborn using the same infusion method, the peak blood level obtained at the end of drip intravenous infusion was 18.0 μg/ml according to BIO and was 14.8 μg/ml according to FIA, and T 1/2 values were 4.76 and 3.68 hours, respectively.
3. As there was a close correlation between the values obtained with BIO and with FIA in both rabbits and clinical cases, with a coefficient of 0.990, and also the BIO values could be estimated using a formula of FIA value × 1.2+2.2, it would be possible to monitor AMK levels in the blood of patients at bedside using the FIA.
4. To 2 newborn patients at 61 and 23 days of age with urinary tract infections due to AMKsensitive E. coli, AMK was administered at a daily dosage of 18.3 and 17.1 mg/kg, respectively, in 3 divided doses by drip intravenous infusion for 30 minutes over a 6-day period. Excellent responses were obtained in both cases. Neither adverse clinical symptoms nor abnormal audiometrical findings were observed in either of the 2. As abnormal laboratory findings, an elevation in GOT and GPT levels was found in 1 but was only transient and was only slight.
