Macrolide Antibiotics

Erythromycin

• Naturally occurring
• First isolated from Streptomyces erythreus

• Erythromycin is primarily bacteriostatic but at high concentrations may act as a bactericidal agent.
• Inhibits bacterial protein synthesis by binding to the 50s ribosomal sub unit.
• Antibacterial activity is increased in alkaline pH.

• Erythromycin is used orally, has incomplete but adequate absorption from the upper part of the GIT.
• Acid labile, hence Enteric Coated.
• Food delays its absorption
• Widely distributes in the body and achieves high concentrations in the prostate.
• It does not cross the Blood Brain Barrier (BBB).
• Metabolised in the liver and excreted in the bile.
• Undergoes Enterohepatic cycling.

• Erythromycin base
• Erythromycin Estolate
• Erythromycin stereate

• Enteral toxicity
• Nausea, vomiting, epigastric distress, diarrhea
• Increases upper gastrointestinal motility by stimulating motilin receptors. (Used in diabetic gastroparesis)
• Hypersensitivity
• Eosinophillia,hepatic toxicity with cholestatic jaundice (especially with Estolate and in pregnant women)

1. Theophylline
2. Carbamazepine
3. Digoxin
4. Wrfarin
5. Cyclosporine
6. Cisapride
7. Astemizole
8. Terfenadine

• Preferred drug in
• Mycoplasma pneumoniae infection (Hastens recovery)
• Legionairre's pneumonia (Azithromycin is preferred)
• Chlamydial infections (Tetracyclines are preferred except in pregnant women and children)
• Diphtheria (eliminates the carrier state; also in acute infection)
• Pertussis (for prophylaxis and infections)

• As alternative to penicillins in allergic patients
• Tetanus
• Streptococcus infections
• Mild staphylococcal infections

• Prophylactic uses
• For recurrence of rheumatic fever
• Prior to surgery to prevent bacterial endocarditis in patients with valvular rheumatic carditis.

• Narrow antibacterial spectrum
• Low oral bioavailability
• Short duration of action
• Poor patient compliance
• Does not cross BBB

Category: Pharmacology Notes