The Effect of Antibiotics on the Metabolism of Certain B Vitamins

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Abstract
The effect of penicillin, aureomycin, streptomycin and terramycin upon the metabolism of thiamine, riboflavin and pantothenic acid was studied in rats. The addition of these antibiotics to the diet (50 mg/kg) caused a marked stimulation of the growth of rats fed diets low in riboflavin and pantothenic acid. A similar effect was observed with penicillin and terramycin added to a low-thiamine diet, but not with aureomycin and streptomycin. The inclusion of the antibiotics in a completely vitamin-supplemented diet had no growth-promoting effect. Growth stimulation was generally associated with increased urinary excretion and a greater liver level of vitamins. Penicillin increased the riboflavin content of the liver, aureomycin the riboflavin excretion in urine, and both aureomycin and penicillin increased the urinary excretion of pantothenic acid when given with non-limiting amounts of these vitamins. Aureomycin, streptomycin and terramycin in a diet low in pantothenic acid, and penicillin added to a diet low in riboflavin, raised the fecal output of these vitamins. Subcutaneous injections of aureomycin and penicillin in rats fed diets low in riboflavin or pantothenic acid, and of penicillin and terramycin in rats on a low-thiamine diet, had no effect on growth or on the accumulation of these vitamins in the liver. It is concluded that the observed sparing effect of antibiotics on the requirement of young rats for certain B vitamins is mainly due to an alteration of the intestinal flora.