Diarrhea, nausea, vomiting, headache, and changes in taste may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: nausea/vomiting that doesn't stop, hearing loss, mental/mood changes, muscle weakness, eye problems (such as drooping eyelids, blurred vision), trouble speaking, severe stomach/abdominal pain, dark urine, yellowing of eyes or skin. This medication may rarely cause a severe intestinal condition due to a bacteria called C. difficile. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop: diarrhea that doesn't stop, abdominal or stomach pain/cramping, blood/mucus in your stool. If you have these symptoms, do not use anti-diarrhea or opioid products because they may make symptoms worse. Use of this medication for prolonged or repeated periods may result in oral thrush or a new yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms. Get medical help right away if you have any very serious side effects, including: severe dizziness, fainting, fast/irregular heartbeat. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: fever that doesn't go away, new or worsening lymph node swelling, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Many drugs besides clarithromycin may affect the heart rhythm (QT prolongation), including amiodarone, disopyramide, dofetilide, pacritinib, pimozide, procainamide, quinidine, sotalol, among others. Other medications can affect the removal of clarithromycin from your body, which may affect how clarithromycin works. Examples include efavirenz, nevirapine, posaconazole, rifamycins (such as rifabutin), among others. Clarithromycin can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include colchicine, digoxin, some drugs used to treat erectile dysfunction-ED/pulmonary hypertension (such as sildenafil, tadalafil), ergot alkaloids (such as ergotamine, dihydroergotamine), flibanserin, some statin drugs (such as lovastatin, simvastatin), tamsulosin, tolvaptan, ticagrelor, among others.