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12 Cards in this Set

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What is the mechanism of action for Macrolides?
Inhibition of 50S subunit by preventing elongation

Bacteriostatic
Resistance to macrolides
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
With what other protein synthesis inhibitor can the macrolids cross react?
Clindamycin

Bind to same spot on the 50S ribosome
Macrolide absorption
25-60%

Erythromycin: not acid stable. Must be coated

Clarithromycin, azithromycin don't require coat
Types of macrolides
Erythromycin
Clarithromycin
Azithromycin
What is the distribution of Macrolides?
Extensive tissue penetration.

No CSF penetration
Macrolide metabolism
Erythromycin, clarithromycin: 2-5 hr

Azithromycin: x > 40 HOURS!!!
Macrolide excretion
Primarily bile
Macrolide adverse effects
GI irritation with erythromycin

Transient deafness with high doses in pts. with renal, hepatic impairment

Hypersensitivity
Erythromycin hypersensitivity reactions
Fever, abdominal pain

Increased serum billirubin

10-20 days post therapy
Erythromycin enzyme interactions
Inhibition of Cytochrome P450 3A4

Decreased metabolism of other drugs requiring P450 (ex: terfenadine, an antihistamine)
Clinical uses of macrolides
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)