Serum erythromycin levels in pregnancy

Area of Science:

• Pharmacology
• Maternal-Fetal Medicine
• Infectious Diseases

Background:

• Erythromycin is the standard treatment for chlamydial infections in pregnant women.
• Limited pharmacokinetic data exists for erythromycin use during pregnancy, especially in the third trimester.

Purpose of the Study:

• To investigate the pharmacokinetic profile of oral erythromycin base in pregnant women, particularly during the third trimester.
• To assess erythromycin absorption and peak serum levels in relation to gestational stage.

Main Methods:

• A study involving 10 pregnant women with chlamydial infection, with 7 in the third trimester and 3 in the second.
• Serum samples were collected at timed intervals (0.5, 1, 2, 3, 4 hours) after a 500-mg oral dose of erythromycin base.
• Analysis focused on determining erythromycin absorption rates and peak serum concentrations.

Main Results:

• Erythromycin absorption was delayed, and peak serum levels were lower in the third trimester compared to second-trimester data.
• Two women in the third trimester had undetectable erythromycin serum levels throughout the study period.
• These two women also reported the most severe gastrointestinal adverse events.

Conclusions:

• Third-trimester pregnancy may be associated with diminished erythromycin absorption and lower serum concentrations.
• Severe gastrointestinal symptoms could be a predictor of subtherapeutic erythromycin levels in late pregnancy.
• Further research is needed to confirm these findings and their clinical implications for chlamydia treatment outcomes.