Clarithromycin (Biaxin) is a prescription antibiotic that was first approved for use in the United States in 1993. Now, more than 3 million prescriptions are filled for the drug every year, according to a 2014 update from the National Library of Medicine, or NLM. This medication is prescribed to treat a range of bacterial infections, from lung, skin, ear and sinus infections to ulcers caused by the bacterium Helicobacter pylori. The most common side effects reported are stomach and intestinal problems, an abnormal taste in the mouth and headaches. Allergic reactions and some severe liver and heart effects also have been reported.
Gastrointestinal Side Effects
An array of different stomach and intestinal symptoms may occur in a person taking clarithromycin. In adults, about 3 percent report experiencing diarrhea and nausea, and 2 percent report indigestion and abdominal discomfort or pain, according to 2013 prescribing information listed by the NLM Daily Med. About 6 percent of people taking extended-release tablets report having diarrhea, the NLM Daily Med also reports. Diarrhea can occur when an antibiotic kills the normal bacteria in the gut, or it can be a sign of an intestinal infection caused by the bacterium Clostridium difficile. This infection is rare, but it has been reported in patients treated with clarithromycin.
Nervous System Effects
A change in the sense of taste, called dysgeusia, is one of the common side effects of clarithromycin and is attributed to its effects on the nervous system. About 3 percent of patients report a strange taste in the mouth, which is often described as metallic, according to NLM Daily Med, which further reports that about 7 percent of people taking extended-release tablets report this side effect. Less commonly, headaches are experienced by people taking clarithromycin. Usually these are mild, but severe headaches have been reported.
Other Side Effects
Effects on the liver, detected by increased levels of blood liver enzymes, have been seen in 1 to 2 percent of patients taking clarithromycin, according to 2014 information from the NLM LiverTox website. It is usually reversible, but liver toxicity can become severe, especially if clarithromycin interacts with other drugs you may be taking. Liver side effects often have no symptoms, and they tend to occur more often in seniors. After clarithromycin was approved for use, clinical trials studying the drug reported insomnia, skin rash and yeast infection side effects in some patients.
If you are pregnant or breastfeeding, you should not take clarithromycin unless your doctor has determined no appropriate alternative treatment is available. Allergic reactions to clarithromycin have been documented and can be serious. Symptoms of an allergic drug reaction may include trouble breathing, wheezing or swelling of the tongue, throat, lips and face. Any of these symptoms should prompt an urgent call to your doctor, as should severe abdominal pain or frequent vomiting; severe, watery or bloody diarrhea; or black or tarry-looking stools. Clarithromycin has been associated with abnormal heart rhythms, most frequently in mature people and women. Your doctor may avoid prescribing this medication if you have heart disease or other risk factors for cardiovascular events.