From the Guidelines
Penicillins, particularly amoxicillin, are generally considered the safest antibiotics during the second trimester of pregnancy. The typical dosage for amoxicillin is 500 mg three times daily for 7-10 days, depending on the infection being treated. Other safe options include cephalosporins like cefuroxime (250-500 mg twice daily) and erythromycin (particularly erythromycin base or ethylsuccinate formulations at 250-500 mg four times daily) 1. These antibiotics have long safety records in pregnancy with no demonstrated increased risk of birth defects or adverse pregnancy outcomes, as supported by the European Respiratory Journal study 1. They work by inhibiting bacterial cell wall synthesis or protein synthesis without affecting fetal development.
When prescribing antibiotics during pregnancy, it's essential to select the narrowest spectrum agent effective against the suspected pathogen to minimize side effects. Always confirm the patient isn't allergic to the prescribed antibiotic, and advise them to complete the full course even if symptoms improve before completion. If gastrointestinal side effects occur, taking the medication with food may help improve tolerance. According to the study, most reports in humans have found no evidence that use of erythromycin during pregnancy is associated with increased risk of birth defects 1.
It's also important to note that certain antibiotics, such as tetracyclines, aminoglycosides, trimethoprim-sulfamethoxazole, and fluoroquinclarines, should be avoided during pregnancy due to potential harm to the fetus, as recommended by the expert panel 1. The European Respiratory Journal study also suggests that doxycycline and erythromycin estolate should be avoided due to potential maternal hepatotoxicity and tooth discolouration in the fetus 1.
In summary, the safest antibiotics to use during the second trimester of pregnancy are penicillins, cephalosporins, and erythromycin, due to their long safety records and minimal risk of birth defects or adverse pregnancy outcomes, as supported by the most recent and highest quality study 1.
From the FDA Drug Label
8 USE IN SPECIFIC POPULATIONS 8. 1 Pregnancy Teratogenic Effects: Reproduction studies have been performed in mice and rats at doses up to 2000 mg/kg (3 and 6 times the 3 g human dose, based on body surface area). There was no evidence of harm to the fetus due to amoxicillin.
Pregnancy: Teratogenic effects In clinical trials with pregnant women, the systemic administration of clindamycin during the second and third trimesters, has not been associated with an increased frequency of congenital abnormalities
- Amoxicillin and clindamycin have been studied in pregnant women, but the evidence is limited.
- The FDA drug labels for amoxicillin 2 and clindamycin 3 do not provide a clear comparison of the safety of these antibiotics during the second trimester of pregnancy.
- Amoxicillin should be used during pregnancy only if clearly needed, and clindamycin should be used during the first trimester of pregnancy only if clearly needed.
- There is no conclusive evidence to determine the safest antibiotic to use during the second trimester of pregnancy.
From the Research
Safest Antibiotics During Pregnancy
The safest antibiotics to use during the second trimester of pregnancy include:
- Penicillins, which are a first-line antibiotic treatment during pregnancy, with the exception of cases in which there is a maternal allergy to penicillin 4, 5, 6, 7
- Cephalosporins, which are another first-line antibiotic used during pregnancy 4, 5, 6
- Erythromycin, which is a macrolide antibiotic that should be preferred during pregnancy 6
- Metronidazole, which is permitted during pregnancy, provided the indications for its use have been strictly verified 4, 7
- Clindamycin, which may be used as a second-line agent during pregnancy 6, 7
Antibiotics to Avoid During Pregnancy
The following antibiotics should be avoided during pregnancy:
- Aminoglycosides, which should not be prescribed at any time during pregnancy due to associated nephrotoxicity and ototoxicity, unless in the event of life-threatening infections with gram-negative pathogens and/or treatment failure of recommended antibiotics 4, 5, 6
- Tetracyclines, which should not be administered to pregnant women after the fifth week of pregnancy, and are deemed contraindicated 4, 5, 6, 7
- Fluoroquinolones, which should be strictly avoided due to potential toxicity for the unborn children 6, 7
- Sulfonamides, which should be avoided during the prepartal period 6
- Chloramphenicol, which should be avoided during the prepartal period 6
- Glycopeptide antibiotics, which should be reserved for life-threatening maternal infections refractory to other antibiotics 6