What antibiotics are safe to use during pregnancy?

Safe Antibiotics During Pregnancy

Amoxicillin, cephalexin, azithromycin, and clindamycin are the safest antibiotics to use during pregnancy, with amoxicillin being the first-line choice for most infections. 1, 2

First-Line Safe Antibiotics

Beta-Lactams

• Amoxicillin: First-line antibiotic during pregnancy (FDA Category B)

  • Dosage: 500 mg orally three times daily 2, 3
  • No evidence of harm to the fetus in human studies 3
  • Commonly used for urinary tract infections and respiratory infections
  • May be combined with clavulanic acid (though plain amoxicillin preferred when possible) 2

• Cephalexin and other cephalosporins:

  • Safe first-line alternatives, especially for those with penicillin allergy (non-anaphylactic) 1, 4
  • Recommended for urinary tract infections and skin/soft tissue infections

Macrolides

• Azithromycin:

  • Safe during pregnancy with moderate evidence 1
  • Useful for respiratory infections and certain STIs
  • Preferred over erythromycin due to better tolerability 1, 5

• Clindamycin:

  • Safe with moderate evidence supporting use 1
  • Particularly useful for bacterial vaginosis and anaerobic infections
  • Can be used as monotherapy for certain infections 1

Second-Line Options (Use with Caution)

• Metronidazole:

  • Can be used if benefits outweigh risks 1
  • Concerns about possible low birth weight and neuroblastoma (low evidence) 1
  • Should be avoided in first trimester if possible 6

• Erythromycin:

  • Generally safe but may cause maternal hepatotoxicity (avoid erythromycin estolate) 1
  • Associated with frequent gastrointestinal side effects that may reduce compliance 1

• Nitrofurantoin:

  • Acceptable for urinary tract infections 5
  • Avoid near term (>36 weeks) due to risk of hemolytic anemia in G6PD-deficient infants

Antibiotics to Avoid During Pregnancy

• Tetracyclines (doxycycline, minocycline):

  • AVOID - Can cause permanent tooth discoloration and inhibit bone growth 1, 4
  • Strong recommendation against use after 5th week of pregnancy 4

• Fluoroquinolones (ciprofloxacin, levofloxacin):

  • AVOID - Contraindicated due to potential cartilage damage in the fetus 4, 6

• Aminoglycosides (gentamicin, tobramycin):

  • AVOID if possible - Risk of ototoxicity and nephrotoxicity 1, 4
  • Use only for life-threatening infections when no alternatives exist 4

• Trimethoprim-Sulfamethoxazole (TMP-SMX):

  • AVOID - Increased risk of birth defects, preterm birth, and kernicterus 1
  • Particularly contraindicated in late pregnancy 1

Special Considerations

Treatment of Sexually Transmitted Infections

• For chlamydia: Azithromycin 1g as single dose is preferred over erythromycin regimens 6
• For gonorrhea: Ceftriaxone is the treatment of choice 6
• Partner treatment is essential to prevent reinfection 1

Antibiotic Selection Algorithm

1. Identify the infection and likely pathogens
2. Choose from first-line safe antibiotics when possible
3. If first-line options are ineffective or contraindicated:
   • Select appropriate second-line agent
   • Use shortest effective duration
   • Monitor closely for adverse effects
4. For severe/life-threatening infections, maternal benefit may outweigh fetal risks

Monitoring During Treatment

• Follow-up within 3-5 days to assess clinical response 2
• Consider test of cure for STIs and certain other infections 6
• Monitor for side effects, particularly gastrointestinal symptoms with erythromycin

Common Pitfalls to Avoid

• Untreated infections pose greater risk to mother and fetus than appropriate antibiotic therapy
• Don't withhold necessary antibiotics due to unfounded fears about fetal effects
• Avoid prescribing tetracyclines or fluoroquinolones even for short courses
• Don't forget to treat partners in cases of STIs to prevent reinfection
• Consider physiological changes of pregnancy that may affect drug pharmacokinetics (increased glomerular filtration rate, increased volume of distribution) 5

Remember that while caution is warranted, untreated infections during pregnancy can lead to serious complications including preterm birth, low birth weight, and spontaneous abortion 5. The benefits of appropriate antibiotic therapy generally outweigh the risks.