Amoxicillin (Amoxil; Polymox; Trimox; Wymox) is a penicillin antibiotic used to treat bacterial infections, especially ear, nose, and throat infections, urinary tract infections, Helicobacter pylori, pneumonia, and skin infections.
Advantages of amoxicillin
Amoxicillin is a very effective agent against many bacterial infections. Because it is available in generic, it is inexpensive. Additionally, it is available in different forms, which makes it accessible to many people: tablet, capsule, and liquid (the liquid comes in many different flavors to make it taste better for people who don’t like pills.)
As we reported here, the American College of Obstetricians has guidelines based on large research studies to help doctors chose the safest antibiotics to use during pregnancy. According to these guidelines, amoxicillin is safe to use during pregnancy and lactation.
Disadvantages of amoxicillin
Although amoxicillin can be used to treat different bacterial infections, many don’t respond to it. In some patients, amoxicillin has been shown to cause diarrhea, nausea, and vomiting. Additionally, except for the extended-release form (which is more expensive because it is branded), you must take amoxicillin 2 to 3 times a day, which can be hard to remember.
Medical studies on amoxicillin use during pregnancy
Amoxicillin and other penicillins accumulate in amniotic fluid after maternal ingestion. This accumulation is caused by fetal urinary excretion of the antibiotic into the amniotic fluid, which continues until the mother stops ingesting the drug. Thereafter, the fetus gradually reabsorbs the antibiotic, probably by swallowing the amniotic fluid, and clears the drug by passage across the placenta to the mother. This does not result in any adverse effect on the fetus. On the contrary, the maternal administration of amoxicillin has been used successfully to eliminate bacterial infection of the amniotic fluid.
Several studies have been conducted on women treated with amoxicillin during the first trimester of gestation and they have shown that the risk of birth defects is not greater than expected in the general population. These include a Taiwanese study of 16 women (Ou et al. 2001), an evaluation of 284 pregnancies with first trimester or 1060 pregnancies with any exposure to ampicillin or amoxicillin (Colley DP, Kay J 1983), a case-control study involving 6935 children with congenital anomalies (Czeizel et al. 2001), a prospective study of 191 women (Berkovitch et al. 2004), and a study using Tennessee Medicaid data in 14,534 children whose mothers were dispensed amoxicillin during pregnancy (Cooper et al. 2009).
However, a Hungarian case-control study reported an elevated risk for amoxicillin use during the second or third gestational month in 1374 pregnancies, leading to the birth of children with isolated cleft lip with or without cleft palate (Puhó et al. 2007). The risk was not increased for cleft palate alone. This observation was replicated in another case-control study (Lin et al. 2012).
Bottom line: amoxicillin was associated in two studies with an increase in facial clefts. Most studies have not suggested an increase in malformations associated with this drug.
Medical studies on amoxicillin use during breastfeeding
Amoxicillin is excreted into human milk in small amounts. A study involving six lactating mothers indicated that peak milk concentrations of amoxicillin occurred between 4 and 5 hours after a 1-g oral dose. Peak milk concentrations of amoxicillin averaged 0.9 mcg/mL (Kafetzis et al. 1981). This exposure is unlikely to have detectable effects in the newborn. This dose of amoxicillin might be sufficient to cause allergic sensitization in the infant.
In a telephone follow-up study, 25 nursing mothers reported taking amoxicillin (dosage unspecified). Three mothers reported diarrhea in their infants. No rashes or candidiasis were reported among the exposed infants (Ito et al. 1993).
A prospective, controlled study asked mothers who called an information service about adverse reactions experienced by their breastfed infants. Of 40 infants exposed to amoxicillin in breastmilk, 2 developed diarrhea and 1 developed a rash (Benyamini et al. 2005).
The use of amoxicillin while breastfeeding was classified as safe by the WHO Working Group on Human Lactation (Bennett and Jensen 1996).
Bottom line: amoxicillin is acceptable to use during breastfeeding. Limited information indicates that single maternal doses of amoxicillin 1 gram produce low levels in milk that are not expected to cause adverse effects in breastfed infants.