Tetracyclines are broad-spectrum bacteriostatic agents with activity a
gainst many gram-positive and gram-negative bacteria as well as Mycopl
asms, Chlamydia, Rickettsiae, and amebas. Doxycycline is the preferred
tetracyline for most indications because it is well absorbed orally,
has excellent tissue penetration, requires no dose adjustment in renal
failure, and has a long-life, making twice-a-day dosing possible. Dox
ycycline is useful for the treatment of atypical pneumonias, sexually
transmitted diseases, Lyme disease, traveler's diarrhea, and rickettsi
al. infections.