Effect of ampicillin or amoxycillin administration on plasma and urinary estrogen levels during normal pregnancy.
Urinary estrogen excretion and plasma levels of conjugated and unconjugated 17 beta-estradiol and estriol were measured in 10 healthy, pregnant women before, during and after a 5-day course of orally administered ampicillin (2 g/day) or the same dose of amoxycillin. On the second and third day of ampicillin treatment the plasma level of conjugated estriol and the urinary estrogen level were lower than pretreatment values, but then returned to basal values despite continuing treatment. Plasma concentrations of conjugated and unconjugated 17 beta-estradiol and of unconjugated estriol did not show any significant change during treatment. Hormone changes in women on amoxycillin were qualitatively similar to but smaller and less consistent than those induced by ampicillin. The results indicate (1) that the use of amoxycillin instead of ampicillin in pregnancies that require estrogen monitoring of feto-placental function, has little clinical advantage, and (2) that the adverse effect of therapeutic doses of ampicillin (and amoxycillin) on estrogen levels during pregnancy may be less important than is commonly assumed.
D000658:Amoxicillin; D000667:Ampicillin; D004958:Estradiol / Q000097:blood*; D004964:Estriol / Q000097:blood*; D004967:Estrogens / Q000652:urine*; D004966:Estrogens, Conjugated (USP) / Q000097:blood; D005260:Female; D006801:Humans; D007700:Kinetics; D011247:Pregnancy
D004967:Estrogens; D004966:Estrogens, Conjugated (USP); D004958:Estradiol; D000667:Ampicillin; D000658:Amoxicillin; D004964:Estriol