Clarithromycin should not be used in pregnant women except in clinical circumstances where no alternative therapy is appropriate. If pregnancy occurs while taking this drug, the patient should be apprised of the potential hazard to the fetus. Clarithromycin has demonstrated adverse effects of pregnancy outcome and/or embryo-fetal development in monkeys, rats, mice, and rabbits at doses that produced plasma levels 2 to 17 times the serum levels achieved in humans treated at the maximum recommended human doses. (See Pregnancy under PRECAUTIONS.)
Pseudomembranous colitis has been reported with nearly all anti-bacterial agents, including clarithromycin, and may range in severity from mild to life threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of anti-bacterial agents. Prolonged or repeated used of clarithromycin may result in an overgrowth of non-susceptible bacterial or fungi. If super infection occurs, clarithromycin should be discontinued and appropriate therapy instituted.