Oral neomycin sulfate and erythromycin base before colon surgery: a comparison of serum and tissue concentrations.

It is accepted that the use of oral neomycin sulfate and erythromycin base before colon surgery results in decreased numbers of intestinal bacteria. Intraluminal levels of these agents are reported to be very high, but systemic availability is still debated. The systemic levels were studied in 8 patients undergoing colon surgery. Each patient received neomycin sulfate and erythromycin base, 1 g each, 19, 18 and 9 hours preoperatively. Twelve samples from serum, one from wound muscle and one from the intestinal wall were obtained from each patient in the 26 hours after the initial dose. Considerable variation was observed among levels. The following means were calculated: peak serum levels were 3.4 and 0.59 micrograms/ml, muscle levels were 1.68 and 0.23 micrograms/g and intestinal wall levels were 6.4 and 12.9 micrograms/g for erythromycin and neomycin respectively. Observed times to peak levels were 19 and 12 hours after the initial dose for erythromycin and neomycin respectively. The detectable systemic concentrations that result when these agents are given orally for bowel preparation before colon surgery may contribute to the drugs' efficacy.