A critical amino acid. A magnesium ion. Doxycycline has a longer half-life than tetracycline, and hence requires less frequent dosing. Doxycycline has greater oral bioavailability than tetracycline. Doxycycline can be taken with antacids while tetracycline cannot.
Doxycycline is less likely to cause teeth mottling compared to tetracycline.
Clostridium difficile overgrowth of the GI tract. Shows bacteriocidal activity against enterococcus. Clarithromycin and erythromycin are both subject to MLS resistance. Clarithromycin has greater oral bioavailability compared to erythromycin. Clarithromycin is more acid stable than erythromycin.