Gentamicin Levels in Pregnant Women with Pyelonephritis

This study was performed at University Medical Center, Lubbock, Texas, from July 1989 to June 1990. We obtained serum gentamicin peak and trough levels in 23 pregnant women with pyelonephritis. The patients were given a loading dose of 2 mg/kg gentamicin, followed by 1.5 mg/kg gentamicin adjusted for obesity every 8 hours. Peak levels were obtained 1 hour after the fifth dose and trough levels were drawn 30 minutes before the sixth dose. Statistical analysis was performed using ₂analysis. The mean (± SD) peak gentamicin level was 2.7 ± 1.4 µg/mL and the mean trough level was 0.5 ± 0.3 µg/mL. Twenty-two of 23 (96%) patients had peak levels 5 µg/mL and 1 of 23 (4%) patients had peak levels between 5 and 10 µg/mL. The mean peak gentamicin level in pregnancy is significantly less than in puerperal women (2.70 versus 5.78; P <0.000001). We conclude that the majority of pregnant women treated for pyelonephritis with standard doses of gentamicin do not achieve therapeutic levels. Also, peak gentamicin levels are significantly below that reported for puerperal women.