Transfer of sisomicin to unborn and suckling guinea pigs.

When guinea pigs received a single intramuscular injection of sisomicin (25 mg/kg) at week 8 of pregnancy, fetal sisomicin concentration at 2 h was highest in the kidneys, followed by the plasma and the cochlea; at 4 h it was not detected in the plasma or the cochlea. When dams were treated with 25 mg/kg during weeks 1-5 of pregnancy, fetal sisomicin concentration in the kidneys was 9 times greater than in the cochlea; in 3-week-old animals, a drug concentration of 4 microgram/g was detected only in the kidneys. When dams were treated during weeks 5-9 of pregnancy, the neonatal drug concentration was highest in the kidneys and the cochlea; no plasma concentration was detected. At 3 weeks of age, the concentration was highest in the kidneys and the cochlea. When lactating dams received sisomicin, only kidneys of suckling animals contained sisomicin at 0.4 microgram/g.