What is the recommended dosage of amoxicillin (amoxicillin) for pregnant women?

Amoxicillin Dosing During Pregnancy

The standard recommended dose of amoxicillin for pregnant women is 500 mg orally every 8 hours (three times daily), which is safe and effective across all trimesters. 1, 2

Standard Dosing Regimens

• 500 mg orally every 8 hours is the most widely recommended dose for pregnant patients across multiple clinical guidelines 1, 2
• Alternative dosing ranges from 250 mg twice daily up to 500 mg three times daily depending on infection severity 1
• The total daily dose range is 40-90 mg/kg/day divided into 2-3 doses, with a maximum of 4000 mg/day 2

Indication-Specific Dosing

Upper Respiratory Tract Infections

• 500 mg orally three times daily for 10 days is recommended by the American College of Obstetricians and Gynecologists and CDC for bacterial upper respiratory infections 2

Chlamydia Trachomatis

• 500 mg orally three times daily for 7-10 days when erythromycin cannot be tolerated 1, 3

Urinary Tract Infections

• 500 mg IV/PO every 8 hours for 3-7 days for uncomplicated UTIs 3

Preterm Premature Rupture of Membranes (PPROM)

• 250 mg orally every 8 hours for 5 days (following initial IV therapy with ampicillin and erythromycin) for PPROM at ≤32 weeks gestation 4
• This regimen is specifically for prolonging pregnancy and decreasing maternal and neonatal morbidity 4

Anthrax Post-Exposure Prophylaxis

• 500 mg every 8 hours for 60 days when susceptibility testing confirms penicillin susceptibility 3

Safety Profile

• Amoxicillin is FDA Pregnancy Category B, indicating it is safe for use throughout pregnancy 1
• Unlike tetracyclines and fluoroquinolones which are contraindicated, amoxicillin has no known teratogenic effects 3
• Amoxicillin is compatible with breastfeeding, though it is distributed into breast milk 1

Critical Dosing Considerations

Physiologic Changes in Pregnancy

• Pregnant women have significantly increased renal clearance of amoxicillin (24.0-24.8 L/h during pregnancy vs. 15.3 L/h postpartum), which may reduce drug concentrations 5
• Maternal serum levels are significantly higher than placental, umbilical cord, and amniotic fluid levels (2.18 vs. 1.00 vs. 1.00 vs. 0.67 µg/g, respectively) 6
• Higher doses may be needed if the target tissue is the fetus or placenta, and intravenous administration should be considered for serious infections 6

Obesity Considerations

• Higher doses should be considered in obese pregnant women due to altered pharmacokinetics 6

Important Contraindications and Cautions

• Never use amoxicillin-clavulanic acid in PPROM due to increased risk of necrotizing enterocolitis in neonates; amoxicillin alone is safe 4
• Known hypersensitivity to penicillins is an absolute contraindication 1
• Avoid concurrent use with tetracyclines due to antagonistic effects 1

Monitoring and Adjustments

• Dose adjustment is required for patients with renal impairment 1
• Monitor for drug interactions with anticoagulants, methotrexate, and probenecid 1
• No specific baseline monitoring is required before initiating therapy 1
• Monitor for common adverse effects including diarrhea, nausea, rash, and oral candidiasis 1

Common Pitfalls to Avoid

• Do not confuse the safety profile of amoxicillin with other antibiotic classes that are contraindicated in pregnancy 3
• Do not use standard non-pregnant dosing without considering increased renal clearance during pregnancy, which may necessitate higher or more frequent dosing for serious infections 5
• Do not prescribe amoxicillin-clavulanic acid for PPROM, as this specific combination increases neonatal morbidity 4