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12 Cards in this Set
- Front
- Back
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What is the mechanism of action for Macrolides?
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Inhibition of 50S subunit by preventing elongation
Bacteriostatic |
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Resistance to macrolides
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Macrolide-Lincosamide-S(b)treptogramin (MLS): Methylation of 50s via changing hairpin structure on macrolide-bound subunits to make methylase start site available
Macrolide (M): efflux of macrolide |
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With what other protein synthesis inhibitor can the macrolids cross react?
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Clindamycin
Bind to same spot on the 50S ribosome |
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Macrolide absorption
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25-60%
Erythromycin: not acid stable. Must be coated Clarithromycin, azithromycin don't require coat |
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Types of macrolides
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Erythromycin
Clarithromycin Azithromycin |
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What is the distribution of Macrolides?
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Extensive tissue penetration.
No CSF penetration |
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Macrolide metabolism
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Erythromycin, clarithromycin: 2-5 hr
Azithromycin: x > 40 HOURS!!! |
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Macrolide excretion
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Primarily bile
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Macrolide adverse effects
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GI irritation with erythromycin
Transient deafness with high doses in pts. with renal, hepatic impairment Hypersensitivity |
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Erythromycin hypersensitivity reactions
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Fever, abdominal pain
Increased serum billirubin 10-20 days post therapy |
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Erythromycin enzyme interactions
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Inhibition of Cytochrome P450 3A4
Decreased metabolism of other drugs requiring P450 (ex: terfenadine, an antihistamine) |
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Clinical uses of macrolides
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Gram positive infections: streptocococcal, staphylococcal infections
No b-lactam allergy activity Others: Atypical pneumonias (mycoplasma, chlamydia, legionella) Mycobacterium avium (immunocomprimised patients, tx. with clar, zaithromycin) |
