Macrolides are used to treat a number of common
They include erythromycin and its derivatives, such
§ 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
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
§ Erythromycin is the drug of choice for
treating Mycoplasmapneumoniae infections
as well as pneumonia caused by
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
§ 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