Imodium vs Pepto-Bismol during pregnancy

How do the options compare?

The two are compared on how much of each reaches the bloodstream, what the pregnancy data actually say, which trimesters carry an explicit caution, and what happens for nursing parents.

• Loperamide is not well studied in pregnancy, and it is not known whether taking it as directed changes the chance of miscarriage, preterm delivery or low birth weight. One study suggested first-trimester use might increase the chance of birth defects and another did not find an increase. 1
• Bismuth subsalicylate can affect how the baby's heart or kidneys work, which may cause oligohydramnios and poor lung development, and may also cause bleeding concerns for the pregnant person. The guidance is to avoid any medication containing salicylate, especially in the second and third trimesters. 1
• In the stomach, bismuth subsalicylate splits into bismuth and salicylic acid, and the salicylate portion is almost completely absorbed into the bloodstream while the bismuth salt is minimally absorbed. Adult dosing runs 524 mg every 30 to 60 minutes, or 1,050 mg hourly at maximum strength, for up to 2 days. 2
• For nursing parents, LactMed advises alternate therapies to bismuth subsalicylate because of possible salicylate absorption by the infant, though infant salicylate intake is estimated at less than 1 percent of the maternal dose. Loperamide is the alternate drug LactMed names for diarrhea. 3
• The FDA recommends not using NSAIDs after 20 weeks of pregnancy unless a healthcare provider specifically recommends it, because NSAID use in the second half of pregnancy might affect the fetal kidneys and the amount of amniotic fluid. 4

Which option makes sense?

Different molecules, different problems. Bismuth subsalicylate carries an explicit avoid-in-pregnancy recommendation because of its salicylate half, while loperamide is barely absorbed but thinly studied, so both roads lead through your provider.

Disclosure: Pregnancy Smart offers a supplement that overlaps with one or more options above. This page describes the pregnancy evidence for each option on its own merits.