Do NOT use Zantac if:

• you are allergic to any ingredient in Zantac
• you have a history of the blood disease porphyria
• you are taking dasatinib.

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with Zantac. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have a history of kidney or liver problems
• if you have abnormal blood electrolyte levels or a history of irregular heartbeat.

Some medicines may interact with Zantac. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Certain benzodiazepines (eg, midazolam, triazolam), glipizide, procainamide, or warfarin because the risk of their side effects may be increased by Zantac
• Dasatinib, delavirdine, gefitinib, certain HIV protease inhibitors (eg, atazanavir), itraconazole, or ketoconazole because their effectiveness may be decreased by Zantac.

This may not be a complete list of all interactions that may occur. Ask your health care provider if Zantac may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

Important safety information:

• Zantac may rarely cause drowsiness, dizziness, or blurred vision. These effects may be worse if you take it with alcohol or certain medicines. Use Zantac with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.
• Zantac may interfere with certain lab tests, including urine protein tests. Be sure your doctor and lab personnel know you are taking Zantac.
• Lab tests, including liver function, may be performed while you use Zantac. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
• Zantac should be used with extreme caution in children younger than 1 month old; safety and effectiveness in these children have not been confirmed.
• Pregnancy and breast-feeding: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Zantac while you are pregnant. Zantac is found in breast milk. Do not breast-feed while taking Zantac.

All medicines may cause side effects, but many people have no, or minor, side effects.

Check with your doctor if any of these most common side effects persist or become bothersome:

Constipation; diarrhea; headache; nausea; stomach upset.

Seek medical attention right away if any of these severe side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue; unusual hoarseness); change in the amount of urine produced; confusion; dark urine; depression; fast, slow, or irregular heartbeat; fever, chills, or sore throat; hallucinations; severe or persistent headache or stomach pain; unusual bruising or bleeding; yellowing of the eyes or skin.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects.