Tetracyclines Pectin

Digoxin is nearly completely absorbed from the gut. In some patients, absorption may be deaeased due to digoxin inactivation by gut bacteria (i.e., Eubacterium lentum) Digoxin absorption is reduced by concomitant administration of antacids, cholestyramine, kaolin/pectin, tetracycline, and neomycin. Radiation malabsorption and gastrointestinal motility drugs such as metoclopramide can also reduce absorption. ... 

Antidiarrheal drugs, such as kaoUn-pectin and bismuth products (176,177), impair the absorption of tetracyclines by chelation (see the interaction with antacids in this monograph). 

Healthy subjects were given tetracycline 250 mg as a solution or as a capsule, with and without 30 rtiL of kaolin-pectin (Kaopectate). The absorption of both formulations was reduced by about 50% by the kaolin-pectin. Even when the kaolin-pectin was given 2 hours before or after the tetracycline, the drug absorption was still reduced by about 20%. The likely reason for this interaction is that tetracycline becomes adsorbed onto the kaolin-pectin so that less is available for absorption. 

---