Effect of Antibiotics on the Serum Cholesterol Concentration of Patients with Atherosclerosis

Oral neomycin, at the dose level of 0.5 to 2 Gm. daily, produced a significant fall in the level of serum cholesterol in all of 29 periods in 20 patients studied. The effect reached a maximum in approximately 2 weeks and persisted for the duration of the experiments up to 9 months. After the medication was discontinued, the serum cholesterol levels returned to control values within 2 weeks. No significant toxic reaction to oral neomycin was discernible. Neomycin by injection in excess of the amount calculated to be absorbed from the gastrointestinal tract failed to lower the serum cholesterol level. The mechanism of action of neomycin was not determined, but it is thought to be a local effect in the gastrointestinal tract or its contents. Oral aureomycin and oral kanamycin had a similar but less marked and less consistent effect on the level of serum cholesterol in a number of patients. In a limited number of patients, oral achromycin, bacitracin, chloromycetin, streptomycin, and mycostatin did not have a significant effect on the serum cholesterol level; likewise, intramuscular penicillin and streptomycin failed to alter the serum cholesterol level. The prior lowering of the serum cholesterol concentration by a low-fat diet did not prevent a further decrease in the serum cholesterol by oral neomycin.