| Indication | For use in the treatment of infections caused by susceptible strains of microorganisms in the following diseases: respiratory tract infections (upper and lower) of mild to moderate degree, pertussis (whooping cough), as adjunct to antitoxin in infections due to Corynebacterium diphtheriae, in the treatment of infections due to Corynebacterium minutissimum, intestinal amebiasis caused by Entamoeba histolytica, acute pelvic inflammatory disease caused by Neisseria gonorrhoeae, skin and soft tissue infections of mild to moderate severity caused by Streptococcus pyogenes and Staphylococcus aureus, primary syphilis caused by Treponema pallidum, infections caused by Chlamydia trachomatis, nongonococcal urethritis caused by Ureaplasma urealyticum, and Legionnaires' disease caused by Legionella pneumophila. |
| Pharmacodynamics | Erythromycin is produced by a strain of Streptomyces erythraeus and belongs to the macrolide group of antibiotics. After absorption, erythromycin diffuses readily into most body fluids. In the absence of meningeal inflammation, low concentrations are normally achieved in the spinal fluid, but the passage of the drug across the blood-brain barrier increases in meningitis. Erythromycin is excreted in breast milk. The drug crosses the placental barrier with fetal serum drug levels reaching 5 - 20% of maternal serum concentrations. Erythromycin is not removed by peritoneal dialysis or hemodialysis. |
| Mechanism of action | Erythromycin acts by penetrating the bacterial cell membrane and reversibly binding to the 50 S subunit of bacterial ribosomes or near the “P” or donor site so that binding of tRNA (transfer RNA) to the donor site is blocked. Translocation of peptides from the “A” or acceptor site to the “P” or donor site is prevented, and subsequent protein synthesis is inhibited. Erythromycin is effective only against actively dividing organisms. The exact mechanism by which erythmromycin reduces lesions of acne vulgaris is not fully known: however, the effect appears to be due in part to the antibacterial activity of the drug. |
| Absorption | Orally administered erythromycin base and its salts are readily absorbed in the microbiologically active form. Topical application of the ophthalmic ointment to the eye may result in absorption into the cornea and aqueous humor. |
| Volume of distribution | Not Available |
| Protein binding | Erythromycin is largely bound to plasma proteins, ranging from 75 - 95% binding depending on the form. |
| Metabolism | Hepatic. Extensively metabolized - after oral administration, less than 5% of the administered dose can be recovered in the active form in the urine. Erythromycin is partially metabolized by CYP3A4 resulting in numerous drug interactions. |
| Route of elimination | Not Available |
| Half life | 0.8 - 3 hours |
| Clearance | Not Available |
| Toxicity | Symptoms of overdose include diarrhea, nausea, stomach cramps, and vomiting. |