This document provides an overview of macrolide antibiotics. It begins by defining macrolides as many-membered lactone rings with attached deoxy sugars. The two most important macrolides are clarithromycin and azithromycin. Macrolides inhibit bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome. They are effective against gram-positive bacteria and spirochaetes but not most gram-negatives. Resistance can develop via plasmid-mediated alterations of the bacterial ribosome binding site. Azithromycin has longer half-life and better tissue penetration than erythromycin or clarithromycin. Unwanted effects include gastrointestinal issues and hypersensitivity reactions.

1. Prof. Shaikh Abusufiyan
Assistant Professor,
AIKTC-School of Pharmacy,
New Panvel-410206
Antibiotics: Macrolide
Pharma Learning Forever

2. At the end of this e-learning session you are able to…
A. Discuss Mechanism of action of
Macrolide
B. Give classification and Explain
pharmacology of Macrolide.
Copyright @shaikhabusufiyan2021

3. Macrolide
• The term 'macrolide'
a many membered lactone ring to which one or more
deoxy sugars are attached.
• Erythromycin --> the first member discovered in the
1950.
• The two most important macrolides are clarithromycin
and azithromycin.

4. MOA
• The macrolides inhibit bacterial protein
synthesis by inhibiting translocation.
• Their action may be bactericidal or
bacteriostatic
the effect depending on the concentration
and on the type of microorganism.

5. • The drugs bind to the 50S subunit of the
bacterial ribosome
• The binding site is the same as that of
Chloramphenicol and Clindamycin
they could compete, if given concurrently.

6. Antimicrobial spectrum
• Very similar to that of penicillin
• Safe and effective alternative for penicillin-
sensitive patients.
• It is effective against
• Gram-positive bacteria and spirochaetes
• But not against most Gram-negative organisms

7. Resistance
• Resistance can occur and results from
a plasmid-controlled alteration of the binding site for
erythromycin on the bacterial ribosome.

8. Azithromycin
• It is less active against Gram-positive bacteria than
erythromycin
• It is considerably more effective against H. influenzae
and may be more active against Legionella.
• It has excellent action against Toxoplasma gondii,
killing the cysts.

9. Clarithromycin
• It is as active, against H. influenzae as
erythromycin.
• But its metabolite has twice activity against H.
influenzae as erythromycin.
• It may be useful in leprosy and against
Helicobacter pylori.

10. Pharmacokinetic aspects:
• The macrolides are administered orally
• Azithromycin and Clarithromycin are more
acid stable than erythromycin.
• Erythromycin can also be given
parenterally.

11. Pharmacokinetic aspects.........
• Do not cross the blood-brain barrier
• It has poor penetration into synovial fluid
• Macrolides are concentrated within phagocytes
• Azithromycin concentrations in phagocyte lysosomes
can be 40 times higher than in the blood
can enhance phagocyte killing of bacteria.

12. Plasma Half life:
• Erythromycin - about 90 minutes
• Clarithromycin - three times longer then
erythromycin
• Azithromycin - 8-16 times longer then
erythromycin

13. Unwanted effect
• Gastrointestinal disturbances with erythromycin
• Hypersensitivity reactions such as:
• skin rashes
• and fever
• Transient hearing disturbances
• Cholestatic jaundice--> rarely, with treatment longer than 2 weeks.
• Opportunistic infections of the gastrointestinal tract or vagina.

14. Reference:
• H.P Rang. M M Dale, J.M Ritter, R.J Flower, G Henderson.
Pharmacology, Seventh Edition. Elsevier Churchill Livengston
Publication. Page no:631-632

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