Macrolides are a class of antibiotics that contain a macrocyclic lactone ring and attached sugars. The commonly used macrolides are erythromycin, clarithromycin, roxithromycin, and azithromycin. They act by inhibiting bacterial protein synthesis by combining with the 50s ribosomal subunits and preventing translocation. Macrolides are bacteriostatic at low concentrations and bactericidal at high concentrations, with a narrow spectrum covering many gram-positive bacteria and some gram-negatives. Newer macrolides include roxithromycin, clarithromycin, azithromycin, and spiramicin.

1. MACROLIDE
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2. WHAT ARE MACROLIDES?
• They are antibiotics having a macrocyclic
lactone ring with attached sugars.
• THE COMMONLY USED MACROLIDES ARE:
Erythromycin
Clarithromycin
Roxithromycin
Azithromycin
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3. ERYTHROMYCIN
• First isolated from Streptomyces erythreus in
1952
• Widely employed as an alternative to
penicillin
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4. MECHANISM OF ACTION
• It is bacteriostatic at low conc & bactericidal at
high conc
• Bactericidal property depends on the
conc, organism concerned and its rate of
multiplication
• Erythromycin acts by inhibiting bacterial
protein synthesis. It combines with 50s
ribosome subunits and prevent translocation.
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5. ANTIMICROBIAL SPECTRUM
• It is a narrow spectrum antibiotic
• Spectrum is similar to Pencillin G. Mostly gram +ve and few
gram –ve bact.
• Str. pyogenes , Str. Pneumonia, N. gonorrhoea, Clostridium, C.
diphtheriae and Listeria
• In addition, Campylobacter, Legionella, Branhamella
catarrhalis, G. vaginalis and Mycoplasma (which are not
affected by pencillin are also highly susceptible to
erythromycin)
• Moderately sensitive to H. ducreyi, H. influenza, B.
pertussis, C. trachomatis, N. meningitidis and Rickettsiae
• Ineffective against Enterobacteriaceae, other gram negative
bacilli and B. fragilis
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6. RESISTANCE
• All cocci develop resistance, mostly by
acquiring capacity to pump it out. Most of the
resistance are plasmid mediated.
• Bacteria that develop resistance to
erythromycin shows cross resistance with
other macrolides.
• Cross resistance with clindamycin and
chloramphenicol can also occur
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7. Pharmacokinetics
• Its acid labile, so protect it from gastric acid its
given as enteric coated tablets
• Erythromycin is widely distributed in the
body, enters cells and into abscesses, crosses
serous membranes and placenta, but not BBB
• Major excretion through liver. Renal excretion
is minor
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8. Adverse Effects
1. Gastrointestinal – epigastric pain, diarrhea
2. Reversible hearing loss
3. Hypersensitivity – fever, rash
Interaction
• It inhibits hepatic oxidation of many drugs – it
rises plasma level of
theophylline, carbamazepine, valproate, ergotami
ne and warfarin
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9. USES
• As an alternative to penicillin
1. Streptococcal pharyngitis, tonsillitis, mastoiditis and CAP
2. Alternative prophylaxis for RF and SABE
3. Diphtheria
4. Tetanus as an adjuvant to TT
5. Syphilis and gonorrhoea
6. Leptospirosis
• As a first choice drug for
1. Atypical pneumonia caused by Mycoplasma
2. Whooping cough
3. Chancroid
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10. NEWER MACROLIDES
• ROXITHROMYCIN
• CLARITHROMYCIN
• AZITHROMYCIN
• SPIRAMYCIN
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