Erythromycin - How It Works
Clinical pharmacology details from the US FDA-approved label: how Erythromycin works in your body, how it's absorbed, how long it stays active, and how it's eliminated.
CLINICAL PHARMACOLOGY Orally administered erythromycin ethylsuccinate suspension is readily and reliably absorbed.
Comparable serum levels of erythromycin are achieved in the fasting and nonfasting states.
Erythromycin diffuses readily into most body fluids.
Only low concentrations are normally achieved in the spinal fluid, but passage of the drug across the blood-brain barrier increases in meningitis.
In the presence of normal hepatic function, erythromycin is concentrated in the liver and excreted in the bile; the effect of hepatic dysfunction on excretion of erythromycin by the liver into the bile is not known.
Less than 5 percent of the orally administered dose of erythromycin is excreted in active form in the urine.
Erythromycin crosses the placental barrier, but fetal plasma levels are low.
The drug is excreted in human milk.
Microbiology Mechanism of Action Erythromycin acts by inhibition of protein synthesis by binding 50S ribosomal subunits of susceptible organisms.
It does not affect nucleic acid synthesis.
Resistance The major route of resistance is modification of the 23S rRNA in the 50S ribosomal subunit to insensitivity while efflux can also be significant.
Interactions with Other Antimicrobials Antagonism exists in vitro between erythromycin and clindamycin, lincomycin, and chloramphenicol.
Antimicrobial Activity Erythromycin has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections (See INDICATIONS AND USAGE ).
Aerobic bacteria Gram-positive bacteria: Corynebacterium diphtheriae Corynebacterium minutissimum Listeria monocytogenes Staphylococcus aureus (resistant organisms may emerge during treatment) Streptococcus pneumoniae Streptococcus pyogenes Gram-negative bacteria: Bordetella pertussis Haemophilus influenzae Legionella pneumophila Neisseria gonorrhoeae Other microorganisms Chlamydia trachomatis Entamoeba histolytica Mycoplasma pneumoniae Treponema pallidum Ureaplasma urealyticum The following in vitro data are available, but their clinical significance is unknown.
At least 90 percent of the following bacteria exhibit in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for erythromycin against isolates of similar genus or organism group.
However, the efficacy of erythromycin in treating clinical infections caused by these bacteria has not been established in adequate and well controlled clinical trials.
Aerobic bacteria Gram-positive bacteria: Viridans group streptococci Gram-negative bacteria: Moraxella catarrhalis Susceptibility Testing For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.