The Influence of Nonabsorbable Antibiotics on Serum Lipids and the Excretion of Neutral Sterols and Bile Acids

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Abstract
The influence of other nonabsorbable antibiotics on serum lipids, the fecal excretion of bile acids and neutral sterols, the digestibility of macronutrients and the stool bacterial content is compared with neomycin. The study was divided into three phases (control, antibiotic and recovery). During the antibiotic phase five healthy volunteer subjects (Neo group) were given neomycin (2.0 gm. daily) and three subjects (Poly group) received a combination of polymyxin B (400 mg. daily) and bacitracin (120,000 units daily). The intestinal flora of subjects given neomycin was altered in that the coliform counts dropped to zero. Although coliform counts in the Poly group did not decrease, the growth pattern was definitely altered. Evidence of a minimal malabsorption state was noted in both groups. Serum lipid phosphorus and total cholesterol values decreased significantly in both groups during the administration of antibiotics. More dramatic changes, however, were noted in the Neo group. A two- to threefold increase in the fecal excretion of total bile acids, and a twofold increase in the fecal excretion of Liebermann-Burchard positive sterols was also noted in both groups during the antibiotic periods. These data are discussed and compared with the results of others. Possible mechanisms of action are evaluated. Although nonabsorbable antibiotics are capable of lowering serum cholesterol and increasing the excretion of cholesterol metabolities, no firm inference may yet be drawn as to the status of total body cholesterol.