| Cimetidine (Tagamet) | Selective histamine H2 antagonist | B | Yes | Potential weak antiandrogenic activity (only observed in animal studies) |
| Famotidine (Pepcid) | Selective H2 antagonist | B | Yes | Limited human data |
| Nizatidine (Axid) | Selective H2 antagonist | B | Yes | Limited human data |
| Ranitidine (Zantac) | Selective H2 antagonist | B | Yes | May be preferable to cimetidine for chronic use |
| Omeprazole (Prilosec) | Proton pump inhibitor | C† | Yes | Most human data suggest it is safe throughout pregnancy |
| Aluminum hydroxide | Antacid | Not available | Not known | Considered safe in pregnancy; risk of neurotoxicity with high doses |
| Calcium carbonate | Antacid | Not available | Yes | Drug of choice; risk of milk-alkali syndrome with high doses |
| Magnesium hydroxide, magnesium carbonate | Antacid | Not available | Not known | Considered safe in pregnancy; magnesium may cause tocolysis in late pregnancy, but this is not a risk with over-the-counter preparations |
| Simethicone (available as a single agent and contained in multiple combination antacids) | Antiflatulent | C | No | Limited data; not absorbed, so considered safe in pregnancy |
| Bismuth subsalicylate (Pepto-Bismol) | Antidiarrheal | C | Not known | Insufficient data; should be avoided during pregnancy, especially in the second and third trimesters because it has a salicylate portion‡ |
| Loperamide (Imodium) | Antidiarrheal | C | Not known | Limited human data; questionable association with cardiovascular defects |
| Mineral oil | Emollient laxative | C | No (not absorbed) | Should be avoided in pregnancy, may interfere with absorption of fat-soluble vitamins§ |
| Castor oil | Laxative/oxytocic | X | Not known | Should be avoided in pregnancy, potential for maternal/fetal morbidity |
| Polyethylene glycol 3350 (Miralax) | Osmotic laxative | C | Not known | Drug of choice for chronic constipation |
