Macrolides are used to treat a number of common infections.
They include erythromycin and its derivatives, such as:
§ erythromycin estolate
§ erythromycin ethylsuccinate
§ erythromycin lactobionate
§ erythromycin stearate.
Other macrolides include:
Because erythromycin is acid-sensitive, it must be buffered or have an enteric coating to prevent destruction by gastric acid. Ery-thromycin is absorbed in the duodenum. It’s distributed to most tissues and body fluids except, in most cases, for cerebrospinal fluid (CSF). However, as a class, macrolides can enter the CSF when meninges are inflamed.
Erythromycin is metabolized by the liver and excreted in bile in high concentrations; small amounts are excreted in urine. It also crosses the placental barrier and is secreted in breast milk.
Macrolides inhibit ribonucleic acid (RNA)–dependent protein syn-thesis by acting on a small portion of the ribosome, much like clin-damycin.
Erythromycin has a range of therapeutic uses.
§ It provides a broad spectrum of antimicrobial activity against gram-positive and gram-negative bacteria, including Mycobacteri-um, Treponema, Mycoplasma, and Chlamydia.
§ It’s also effective against pneumococci and group A streptococ-ci. Staphylococcus aureus is sensitive to erythromycin; however, resistant strains may appear during therapy.
§ Erythromycin is the drug of choice for treating Mycoplasmapneumoniae infections as well as pneumonia caused by Legionel-la pneumophila.
In the patient who’s allergic to penicillin, erythromycin is effective for infections produced by group A beta-hemolytic streptococci or Streptococcus pneumoniae. It may also be used to treat gonor-rhea and syphilis in the patient who can’t tolerate penicillin G or the tetracyclines. Erythromycin may also be used to treat minor staphylococcal infections of the skin.
Azithromycin provides a broad spectrum of antimicrobial activity against gram-positive and gram-negative bacteria, including My-cobacterium, S. aureus, Haemophilus influenzae, Moraxella ca-tarrhalis, and Chlamydia. It’s also effective against pneumococciand groups C, F, and G streptococci.
§ Clarithromycin is a broad-spectrum antibacterial that’s active against gram-positive aerobes, such as S. aureus, S. pneumoniae, and Streptococcus pyogenes; gram-negative aerobes, such asH. influenzae and M. catarrhalis; and other aerobes such aspneumoniae.
§ Clarithromycin has also been used in combination withantacids, histamine-2 blockers, and proton pump inhibitors to treat Helicobacter pylori–induced duodenal ulcer disease.
Macrolides may interact with these drugs.
§ Erythromycin, azithromycin, and clarithromycin can increase theophylline levels in the patient receiving high dosages of theo-phylline, increasing the risk of theophylline toxicity.
§ Clarithromycin may increase the concentration of carba-mazepine when used together. (See Adverse reactions tomacrolides.)