Ilosone 200/Ilosone DS Mechanism of Action

Antibacterial (Macrolide).
Pharmacology: Ilosone DS: Orally administered erythromycin estolate is readily and reliably absorbed. Because of acid stability, serum levels are comparable whether the estolate is taken in the fasting state or after food. After a single 250 mg dose, blood concentrations average 0.29, 1.2 and 1.2 mg/L respectively at 2, 4 and 6 hours. Following a 500 mg dose, blood concentrations average 3, 1.9 and 0.7 mg/L respectively at 2, 6 and 12 hours.
After oral administration, serum antibiotic levels consist of erythromycin base and propionyl erythromycin ester. The propionyl ester continuously hydrolyzes to the base form of erythromycin to maintain an equilibrium ratio of approximately 20% base and 80% ester in serum.
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 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 of excretion of erythromycin by the liver into the bile is not known. After oral administration, less than 5% of the administered dose can be recovered as the active form in the urine.
Erythromycin crosses the placental barrier but fetal plasma levels are low. The drug is excreted in human milk.
Pharmacokinetics: Ilosone 200: Orally administered erythromycin ethylsuccinate suspensions and film-coated tablets are 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: Ilosone DS: Erythromycin inhibits protein synthesis without affecting nucleic acid synthesis. Some strains of Haemophilus influenzae and staphylococci have demonstrated resistance to erythromycin. Some strains of H. influenzae that are resistant in vitro to erythromycin alone are susceptible to erythromycin and sulfonamides used concomitantly. If the Bauer-Kirby method of disk susceptibility testing is used, a 15-μg erythromycin disk should give a zone diameter of at least 18 mm when tested against an erythromycin-susceptible organism.
Antagonism has been demonstrated between clindamycin and erythromycin.
Ilosone 200: Erythromycin acts by inhibition of protein synthesis by binding 50S ribosomal subunits of susceptible organisms. It does not affect nucleic acid synthesis. Antagonism has been demonstrated in vitro between erythromycin and clindamycin, lincomycin, and chloramphenicol. Many strains of Haemophilus influenzae are resistant to erythromycin alone but are susceptible to erythromycin and sulfonamides used concomitantly. Staphylococci resistant to erythromycin may emerge during a course of therapy. Erythromycin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in Indications/Uses section.