Erythromycin

Erythromycin exerts its antimicrobial action by binding to the 50S ribosomal sub-unit of susceptible microorganisms and suppresses protein synthesis. Erythromycin is usually active against most strains of the following organisms both in vitro and in clinical infections.

Gram positive bacteria:

Listeria monocytogenes
Corynebacterium diphtheriae (as an adjunct to antitoxin)
Staphylococci spp.
Streptococci spp. (including Enterococci)

Gram negative bacteria:

Haemophilus influenzae
Neisseria meningitidis
Neisseria gonorrhoeae
Legionella pneumophila
Moraxella (Branhamella) catarrhalis
Bordetella pertussis
Campylobacter spp.

Mycoplasma:

Mycoplasma pneumoniae
Ureaplasma urealyticum

Other organisms:

Treponema pallidum
Chlamydia spp.
Clostridia spp., L-forms, the agents causing trachoma and lymphogranuloma venereum

Note: The majority of strains of Haemophilus influenzae are susceptible to the concentrations reached after ordinary doses.

Oral administration

Absorption is facilitated if the stomach is empty.

Peak blood levels normally occur within 1 hour of dosing of erythromycin ethylsuccinate granules. The elimination half life is approximately 2 hours. Doses may be administered 2, 3 or 4 times a day.

Erythromycin ethylsuccinate is less susceptible than erythromycin to the adverse effect of gastric acid. It is absorbed from the small intestine. It is widely distributed throughout body tissues. Little metabolism occurs and only about 5% is excreted in the urine. It is excreted principally by the liver.

The drug is not removed by either peritoneal dialysis or haemodialysis. It diffuses readily into intracellular fluids and antibacterial activity can be achieved at essentially all sites. There is some retention on liver and spleen. Only low concentrations are achieved in cerebrospinal fluid, unless the meninges are inflamed. Diffusion into the aqueous humour, but not the vitreous humour of the eye is good. A significant proportion is bound to serum proteins.

There are no preclinical data of relevance to the prescriber, which are additional to that already included in the other sections.