What Are Macrolides?

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  • Written By: Clara Kedrek
  • Edited By: Jessica Seminara
  • Last Modified Date: 23 October 2019
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Macrolides are a class of medications that have a macrolide ring as part of their chemical structure; this ring structure is what gives the drugs their chemical activity. These pharmaceuticals are used either to treat bacterial infections or to decrease the activity of the body’s immune system. Although medications in this class can have a number of side effects, they are commonly prescribed because the good they do outweighs their possible adverse effects.

Many macrolides are used as antibiotic medications, and fight infection by inhibiting the ability of bacteria to make proteins. Examples of antibiotic macrolides include clarithromycin, erythromycin, and azithromycin. Without their protein-producing capability, bacteria are not able to reproduce. As a result, bacteria levels are stabilized, and eventually decrease with continued antibiotic use. The clinical symptoms associated with the bacterial infection decrease as the bacteria die off.

A number of bacterial infections can be treated with macrolides. They are commonly used to treat respiratory tract infections such as pneumonia, bronchitis, and sinusitis. Many genitourinary infections such as pelvic inflammatory disease, chlamydia, and urinary tract infections also respond well to these antibiotics. Other uses include treating traveler’s diarrhea and skin infections.


Side effects caused by the macrolide antibiotics are typically mild, but can include diarrhea, nausea, rash, and headache. Patients with myasthenia gravis, low blood potassium, or renal impairment should use caution in taking these medications, as they could experience more severe side effects. These antibiotic medications are only available by prescription in the United States.

Another use for macrolides are as immunosuppressive agents. The mechanism of action of these medications differs from how the antibiotic macrolides work. Immunosuppresive macrolides inhibit the activation of T cells, which are a type of white blood cell important in protecting the body from harm. Decreased T cell activity results in suppression of the immune system. The non-antibiotic macrolides include tacrolimus, pimecrolimus, and sirolimus.

The immunosuppressive macrolides are important in treating a number of conditions. One use of these drugs is to suppress the immune system of patients receiving organ transplants. Without immunosuppressive agents, the recipient’s immune system could reject the transplanted organ. Another use of the medications is to treat a variety of autoimmune diseases such as ulcerative colitis and psoriasis. In these conditions, the immune system is attacking the body, and suppressing the action of the immune system results in decreased symptoms.

Adverse reactions from these immunosuppressive agents are typically more severe compared to their antibiotic counterparts. They can decrease blood counts, increase the risk for infection, and cause cardiac arrhythmias. Often these drugs are only prescribed by specialists such as rheumatologists or physicians trained in transplant medication.


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