Allergic reaction to penicillins or other β-lactams. Prolonged use may result in the overgrowth of other nonsusceptible organisms (eg, Candida, Enterococci, Clostridium difficile
). Consider diagnosis of pseudomembranous colitis in patients who develop serious diarrhea. Direct Jarisch-Herxheimer reaction following Lyme disease treatment. May impair ability to drive or operate machinery. Pregnancy & lactation.