Key takeaways
Cimetidine (Tagamet HB) and famotidine (Pepcid AC) are both histamine H2 receptor antagonists (H2RAs) used to reduce stomach acid, but they have some differences. Cimetidine and famotidine are available over-the-counter (OTC) and by prescription. Famotidine OTC is available under brand names like Pepcid AC and Zantac 360. Cimetidine can be taken up to four times a day, whereas famotidine is typically taken one to two times a day. Cimetidine has more drug interactions compared to famotidine, which might make famotidine a safer option if you are taking multiple medications. Common side effects for both include headache and dizziness, but cimetidine can also cause diarrhea, while famotidine might cause constipation. Additionally, cimetidine is sometimes used off-label for conditions like molluscum contagiosum (wart-like viral rash), whereas famotidine is generally used for heartburn and ulcers.
