3. ⢠Belong to the Polyketide class of natural
products.
⢠A group of antibiotics consisting of a
macrolide ring
⢠A large lactone ring to which one or more deoxy
sugars, are attached.
⢠The lactone ring can be either 14, 15 or 16
membered.
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4. ⢠Naturally-occurring macrolide derived from
Streptomyces erythreus
⢠Problems with erythromycin
⢠Acid labile
⢠Narrow spectrum
⢠Poor GI tolerance
⢠Short elimination half-life
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6. ⢠Inhibits protein synthesis by reversibly
binding to the 50S ribosomal subunit
⢠Suppression of RNA-dependent protein
synthesis by inhibition of translocation of
mRNA
⢠Typically bacteriostatic activity
⢠Bactericidal at high concentrations against
very susceptible organisms
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9. Gram-Positive Aerobes :
Erythromycin & clarithromycin display the best activity
(Clarithro>Erythro>Azithro)
⢠Methicillin-susceptible Staphylococcus aureus
⢠Streptococcus pneumoniae (only PSSP) â
resistance is developing
⢠Group and viridans streptococci
⢠Bacillus sp.
⢠Corynebacterium sp.
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10. Gram-Negative Aerobes â Newer macrolides
with enhanced activity
(Azithro>Clarithro>Erythro)
⢠H. influenzae (not erythro),
⢠M. catarrhalis,
⢠Neisseria sp.
⢠Do NOT have activity against any Enterobacteriaceae
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14. Absorption
ďErythromycin â variable absorption, food may
decrease the absorption
⢠Base: destroyed by gastric acid; enteric coated
⢠Esters and ester salts: more acid stable
ďClarithromycin â acid stable and well-absorbed
regardless of presence of food
ďAzithromycin âacid stable; food decreases
absorption of capsules
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15. Distribution
ďś Extensive tissue and cellular
distribution
ďś clarithromycin and azithromycin with
extensive penetration
ďś Minimal CSF penetration
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16. Elimination
ďś Clarithromycin is the only macrolide partially
eliminated by the kidney (18% of parent and all
metabolites)
ďś Hepatically eliminated: ALL
ďś NONE of the macrolides are removed during
hemodialysis !....
ďś Variable elimination half-lives
ďś 1.4 hours for erythr
ďś3 to 7 hours for clarithro;
ďś 68 hours for azithro
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17. ⢠Gastrointestinal â up to 33 %
ďNausea, vomiting, diarrhea, dyspepsia
ďGastic pain, cramps
ďMost common with erythro; less with new agents
⢠Cholestatic hepatitis - rare
ď > 1 to 2 weeks of erythromycin estolate
⢠Thrombophlebitis â IV Erythro and Azithro
ďDilution of dose; slow administration
⢠Other: Ototoxicity (high dose erythro );
QTc prolongation;
Allergy
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18. Erythromycin and Clarithromycin ONLYâ
are inhibitors of cytochrome p450 system
in the liver; may increase concentrations
of:
Theophylline Digoxin, Disopyramide
Carbamazepine Valproic acid
Cyclosporine Terfenadine, Astemizole
Phenytoin Cisapride
Warfarin Ergot alkaloids
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20. ⢠Strep/Staph Infections; alternatives in
patients allergic to Penicillin
⢠Prophylaxis against endocarditis in dental
procedures
⢠Campylobacter/ Helicobacter Infections
:clarithro
⢠Tetanus: in patients allergic to Penicillin
⢠Mycobacterial Infections: Clathri / Azithro Ist
choice
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21. âDrug of Choiceâ for
ďą Mycoplasma pneumoniae
ďąLegionella pneumophila
ďą Chlamydia pneumoniae, C. trachomatis
ďąBordetella pertussis (whooping cough)
ďąC. diphtheriae
Esters of erythromycin -sterate/estolate/ethylsuccinate
are resistant to inactivation.
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22. ⢠Advantages :
⢠Broader spectrum, higher activity
⢠Orally effective
⢠High blood concentration
⢠Longer t 1/2
⢠Less toxicity
⢠Mainly used in respiratory tract infection
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23. ⢠Strongest activity against mycoplasma pneumoniae.
⢠Less effective against gram (+) bacteria than erythro
/clarithro.
⢠More effective on Gram-negative bacteria,
H.influenzae, Legionella.
⢠Excellent action against Toxoplasma gondii
⢠Well tolerated
⢠T1/2 :35~48h once daily
⢠Mainly used in respitory tract infection
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24. ⢠Excellent tissue concentration : 10- to 100-
fold higher conc. than serum
⢠prolonged persistence of good conc. in
cells
⢠3- or 5-days therapy is possible (except for
severe Legionella pneumonia)
⢠Pregnant women infected with Scrub typhus :
Azithromycin can substitute for doxycycline
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