Recognizing and Managing AB-Induced Diarrhea

Incidence: 5-10% c oral ampicillin (amcill, ampicin); 10-25% c amoxicillin-clavulanate (Augmentin); 15-20% c cefixime (Suprax); 2-5% c Fluoroquinolones, azithromycin, clarithromycin, tetracycline; rate of parenteral administered AB similar to that seen P.O.; 10-20% of AB incuced diarrhea is associated c C. difficile.

Nuisance diarrhea: frequent, loose watery stools with no complications; usually emerges during AB regimen (as opposed to C. difficile induced pseudomembranous enterocolits which emerges after regimen completion).

Colitis: abdominal cramping, fever, leucocytosis, fecal leukocytes.

Mechanisms are independent of antimicrobial action on the gut.

Erythromycin acts to accelerate gastric emptying

Clavulanate: this beta-lactamase inhibitor stimulates bowel motility related to action on gut microbe flora.

Orally administered ABs reduce the concentration of normal fecal anaerobes with the consequence that carbohydrate metabolism is decreased, leading to osmotic diarrhea. Other action may include direct action on intestinal mucosa.

Managements: usually self-limiting for short term tx regimens used in dentistry; if severe and persistent, discontinue use; if diarrhea persists after discontinuation, consider C. difficile infection and tx for 10 days c metronidazole or vancomycin (CDC protocol); failure to respond to either metronidazole (Flagyl) or vancomycin suggests that the diarrhea is not caused by C. difficile.

The moral of all this is that you must be familiar with infectious diseases and symptoms of pseudomembranous colitis. Deaths can occur from improper management.

Category: Pharmacology Notes