Clarithromycin is an antibiotic that is used to treat many different types of bacterial infections affecting the skin and respiratory system.

Clarithromycin is also used together with other medicines to treat stomach ulcers caused by Helicobacter pylori.

Clarithromycin may also be used for purposes not listed in this medication guide.

You should not use this medicine if you are allergic to clarithromycin or similar medicines such as azithromycin (Zithromax, Z-Pak, Zmax), erythromycin, or telithromycin, or if:

• you have had jaundice or liver problems caused by taking clarithromycin; or
• you have liver or kidney disease and you also take a medicine called colchicine.

Some medicines can cause unwanted or dangerous effects when used with clarithromycin. Your doctor may change your treatment plan if you also use:

• cisapride;
• lomitapide;
• pimozide;
• lovastatin or simvastatin; or
• ergotamine or dihydroergotamine.

Tell your doctor if you have ever had:

• heart problems;
• long QT syndrome (in you or a family member);
• coronary artery disease (clogged arteries);
• myasthenia gravis;
• liver disease;
• kidney disease;
• diabetes; or
• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood).

Clarithromycin may harm an unborn baby. Use effective birth control to prevent pregnancy while you are using this medicine. Tell your doctor if you become pregnant.

In animal studies, clarithromycin caused birth defects. However, it is not known whether these effects would occur in humans. Ask your doctor about your risk.

It may not be safe to breast-feed a baby while you are using this medicine. Ask your doctor about any risks.

Clarithromycin is not approved for use by anyone younger than 6 months old.

Use Biaxin XL-Pak (Oral) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning in your eyes, skin pain, red or purple skin rash that spreads and causes blistering and peeling).

Call your doctor at once if you have:

• severe stomach pain, diarrhea that is watery or bloody;
• fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness (like you might pass out);
• confusion, spinning sensation;
• liver problems--loss of appetite, upper stomach pain, tiredness, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
• kidney problems--little or no urination, swelling in your feet or ankles, feeling tired or short of breath.

Older adults may be more likely to have heart rhythm side effects, including a life-threatening fast heart rate.

Common side effects may include:

• stomach pain, nausea, vomiting;
• diarrhea; or
• unusual or unpleasant taste in your mouth.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Antibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or bloody, call your doctor. Do not use anti-diarrhea medicine unless your doctor tells you to.