Generic Zantac

Common use

Zantac is a blocker of H2-histamine receptors. The mechanism of action consists in the blockade of histamine H2-receptors of parietal cells in gastric mucous layer. This medication suppresses day and night secretion of HCl (both basal and stimulated), reduces the amount of gastric juices caused by stretching of the stomach with food load and by the action of hormones and biogenic stimulants such as gastrin, histamine, acetylcholine, pentagastrin, caffeine. Zantac reduces the amount of HCl in gastric juice almost without suppressing "liver" enzymes associated with cytochrome P450. It does not affect the concentration of gastrin in plasma, production of mucus. Zantac reduces pepsin activity. This medication is use to treat and prevent stomach and duodenal ulcers, gastrointestinal disorders caused by NSAID, heartburn, hypersecretion of gastric juice, symptomatic ulcers, ulcers caused by stress, erosive esophagitis, reflux esophagitis, Zollinger-Ellison syndrome and other conditions.



Dosage and direction

Take it orally with or without food. Correction of the dose should be made in patients with significantly abnormal liver or kidney function. Besides tablets this medication maybe administered intramuscularly (IM) or intravenously.



Precautions

The Zantac effervescent tablet may contain phenylalanine. Notify your doctor if you are pregnant, plan to become pregnant or breastfeeding before to take Zantac. Risk of developing pneumonia may be increased by this medication.



Contraindications

Hypersensitivity, breastfeeding. In patients with liver of kidney failure, cirrhosis of the liver, acute porphyria (also in history), children younger than 12 y.o., pregnancy this medication should be administered with cautiousness.



Possible side effect

Besides possible allergy (hives, rash, swelling most common side effects of Zantac are constipation, diarrhea, fatigue, headache, insomnia, muscle pain, nausea, and vomiting. Rare more serious side effects are agitation, anemia, confusion, depression, easy bruising or bleeding, hallucinations, hair loss, irregular heartbeat, visual changes, jaundice.





Drug interaction

Antacids may decrease the absorption of Zantac, so their intake should be separated by 1-2 hours. Alcohol levels may increase if Zantac is taken simultaneously. This medication also increases the area under the plasma concentration time curve (AUC) and concentration of Metoprolol in blood serum, slows absorption of itraconazole and ketoconazole.



Missed dose

If you missed a dose take it as soon as you remember, but not if it is almost time of the next intake by your schedule. If so skip the missed dose. Do not try to compensate a missed dose by taking an extra one.





Overdose

If you suspect that you took too much of the medication seek for immediate medical attention. Symptoms of overdose include lack of coordination, feeling light-headed, or fainting.



Storage

Save Zantac in a dry place away from sunlight at room temperature between 15-30 C (59-86 F).



Disclaimer

We provide only general information about medications which does not cover all directions, possible drug integrations, or precautions. Information at the site cannot be used for self-treatment and self-diagnosis. Any specific instructions for a particular patient should be agreed with your health care adviser or doctor in charge of the case. We disclaim reliability of this information and mistakes it could contain. We are not responsible for any direct, indirect, special or other indirect damage as a result of any use of the information on this site and also for consequences of self-treatment.

Clinical Verification

Last Clinically Updated: August 15, 2026

Written By

Dr. Elena Vance, PharmD

Clinical Specialist in Neuropharmacology

Fact Checked By

Marcus Thorne, MS

Biomedical Data & FDA Label Verification

Medically Reviewed By

Dr. Arthur Campbell, MD

Board-Certified Psychiatrist (ABPN)