Pulsed dosing and extended daily dosing of oral vancomycin do not facilitate clearance ofcolonization in mice.

Abstract

Vancomycin taper and pulse regimens are commonly used to treat recurrentinfections, but the mechanism by which these regimens might reduce recurrences is unclear. Here, we used a mouse model to test the hypothesis that pulse dosing of vancomycin after a 10-day treatment course enhances clearance offrom the intestinal tract. Mice withcolonization received 10 days of once-daily oral vancomycin followed by 20 days of treatment with saline (controls), daily vancomycin, or pulse dosing of vancomycin every 2 or 3 days. Stool samples were collected to measure the concentration of C.during and after treatment, vancomycin concentrations, and growth of vegetativeduring every 3 days dosing. Pulse dosing of vancomycin was not effective in maintaining suppression of(> 0.05 in comparison to saline controls); growth of vegetativeoccurred between pulse doses when vancomycin decreased to undetectable levels. Daily dosing of vancomycin suppressedduring treatment, but recurrent colonization occurred after treatment in more than 75% of mice, and by post-treatment day 14, there was no significant difference among the control, pulse dosing, and daily dosing groups (> 0.05). These findings demonstrate that pulse dosing of vancomycin every 2 or 3 days does not facilitate the clearance ofspores in mice. Studies are needed to examine the impact of vancomycin taper and pulsed regimens in patients.