Clarithromycin is the generic name for an oral antibacterial medication marketed under the brand name of Biaxin®. Common uses of clarithromycin include treatment for certain ulcers, legionnaires' disease and infections caused by bacteria. Other drugs, foods and pre-existing conditions can all interact with the medication. Some of these interactions are mild, but others can be life threatening. One of the greatest risks of clarithromycin is an interaction with drugs such as blood thinners, heart medications, statins, pain relievers and sedatives, as well as certain medications for erectile dysfunction or seizures.
Many drugs that are safe at normal dosages can become toxic when combined with clarithromycin. The antibacterial affects how well the liver processes toxins and this reduction in liver function can lead to dangerous build-ups of a drug in the body. Clarithromycin interactions have been reported with carbamazepine, chlordiazepoxide, diazepam, colchicine and ergot-based drugs, such as migraine medications.
Clarithromycin interactions are also possible when the antibacterial is taken with drugs used to regulate the heartbeat, such as digoxin. This is due to the fact that clarithromycin can alter the rhythm by itself. When combined with other medications that also alter the heart rate, a potentially serious condition, known as QT prolongation, may result. Patients taking digoxin or similar medications are at greatest risk for clarithromycin interactions that affect the cardiovascular system. As patients with low potassium or magnesium levels have an elevated risk of QT prolongation, patients who have depleted levels or who take diuretics, which can lower these levels, should discuss the use of clarithromycin with their doctors.
One of the potential side effects of blood thinners such as warfarin is an increased risk of bruising and bleeding. Clarithromycin can cause the drug to thin the blood too much. Nosebleeds have been reported, but instances of internal bleeding have also been reported, some of them quite severe.
Potentially serious clarithromycin interactions have also been reported in patients who were taking theophylline, pimozide, ranitidine, terfenadine, vardenafil, nevirapine and atazanavir. Some reports of impaired thinking and sleep disturbances have been attributed to an interaction with triazolam. Other drugs, such as itraconazole and saquinavir, result in two-way clarithromycin interactions in which the effectiveness of both drugs are affected.
Patients with liver or kidney disease should be carefully monitored if their doctors choose to prescribe clarithromycin as the antibacterial can reduce these organs' ability to remove toxins. Special attention must be given to those with impaired kidney or liver function if they are taking any medications to safeguard against clarithromycin interactions. Typically, doctors are also reluctant to prescribe clarithromycin to patients with myasthenia gravis, a disorder that causes muscle weakness.