NAPLEX Practice Question # 23

NAPLEX Examination.

Practice Question # 23.




Alternatives to erythromycin

Clarithromycin and azithromycin (Zithromax) are semisynthetic macrolide antibiotics. Th ese expensive but well-tolerated alternatives to erythromycin are administered once daily.


  • Spectrum of activity. Clarithromycin is more active than erythromycin against staphylococci and streptococci. In addition to activity against other organisms covered by erythromycin, it is also active in vitro against MAI, Toxoplasma gondii, and Cryptosporidium spp.
  • Th erapeutic uses. Th is agent is indicated for the prevention of Mycobacterium avium complex (MAC) infection and is useful in otitis media, sinusitis, mycoplasmal pneumonia, and pharyngitis. Clarithromycin is also used with proton pump inhibitors (PPIs) for Helicobacter pylori eradication.


  • Spectrum of activity. Azithromycin is less active than erythromycin against grampositive cocci but more active against H. infl uenzae and other gram-negative organisms. Azithromycin concentrates within cells, and tissue levels are higher than serum levels.
  • Th erapeutic uses. Th is agent is useful in nongonococcal urethritis caused by chlamydia, lower respiratory tract infections, Mycobacterium avium-intracellulare (MAC or MAI) infection and prophylaxis, pharyngitis, pelvic infl ammatory disease, and Legionnaires disease. Azithromycin is also indicated for pediatric use.

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