Macrolides

Question 1

Macrolides and Ketolides

Answer 1

Clarithromycin
Azithromycin
Erythromycin

Telithromycin

Used most often in outpatient setting because of broad coverage of respiratory pathogens
Coverage is broad but not deep
Increasing resistance (especially S. pneumoniae)

Telith developed against this resistance
Has significant risk of hepatotoxicity

Erythromycin rarely used anymore except as GI stimulant due to adverse effects, drug interactions, and frequent dosing

Question 2

Macrolides and Ketolides MOA

Answer 2

Bind to bacterial ribosomes (50s subunit) preventing the ribosomes from shuffling along and adding a new amino acid to the elongating protein chain

Question 3

Macrolides and Ketolides Spectrum

Answer 3

Good
Atypicals
H. influenzae
Moraxella catarrhalis
H. pylori
Mycobacterium avium

Moderate
S. pneumoniae (Telith > macrolides)
S. pyogenes

Poor
Staph
Enteric GNRs (azithromycin > clarithromycin)
Anaerobes
Enterococci

Question 4

Macrolides and Ketolides Adverse Effects

Answer 4

GI
Significant GI effects (N/V/D)
Erythromycin is worst offender (used as a prokinetic agent for patients with impaired GI motility)

Hepatic
Rare but serious adverse hepatic effects with macrolides
Telith associated with hepatic failure leading to death or need for transplantation

Cardiac
Prolongation of QT interval (Erythromycin most common)
Use with caution in patients with pre-existing heart conditions, on anti-arrhythmic drugs, or on interacting drugs

Question 5

Macrolides and Ketolides Important Facts

Answer 5

Potent inhibitors of cytochrome P450 enzymes (except azithromycin)

Azithromycin has a prolonged half life; short course adequate for most infections

Bacteriostatic drugs; not appropriate for infections where cidal activity is usually required (meningitis, endocarditis)

Prevpac- for eradication of H. pylori and treatment of peptic ulcer disease
Contains clarithromycin, lansoprazole, and amoxicillin
Screen for beta lactam allergy and drug interactions

Their spectrum makes an ideal choice for CA pneumonia
Only good for monotherapy mild disease due to high rates of resistance; treat more fragile patients with something else or add beta lactam active against S. pneumoniae

Question 6

Macrolides and Ketolides Good For

Answer 6

Upper and lower respiratory tract infections
Chlamydia
Atypical mycobacterial infections
Traveller’s diarrhea (azithromycin)
H. pylori induced GI ulcer disease (clarithromycin in combo with other drugs and acid suppressive agents)