Zantac (Ranitidine HCI) Gastrointestinal agent Histamine H2 antagonist Duodenal and Gastric Ulcer (short-term treatment), maintenance therapy in Duodenal Ulcer, self-medication for relief of occasional heartburn, acid Indigestion, and sour stomach, stomach ulcers, heatburn, inflammation and erosion of the esophagus, Reflux disease. 150 mg once to twice daily as directed by physician, take before or after meals. Category B Headache, dizziness, Insomnia, vertigo, confusion, Constipation, abdominal pain, rash, increased serum Creatinine level, reversible leukopenia, pancytopenia, granulocytopenia, jaundice, anaphylaxis. Pregnancy Risk Categories defined: A: Studies in pregnant women failed to show a risk to the fetus in the first trimester - with no evidence of risk in the later trimesters. B: Animals studies indicate no adverse effect to the fetus, but there are no adequate, clinical studies in pregnant women. C: Animal studies have shown an adverse effect on the fetus, but there are no adequate, clinical studies in humans. Despite potential risks, the drug may be useful in pregnant women. D: There is evidence of risk to the human fetus, but the potential benefits of use in pregnant women may be acceptable, despite potential risks. X: Studies in animals or humans show fetal abnormalities, or adverse reaction reports indicate evidence of fetal risk. Warning: the risks involved clearly outweigh any potential benefit from using the drug in pregnant women, regardless of trimester. NR: Not rated (i.e., no information available at this time as to the potential risks or benefits).