Systemic absorption of oral vancomycin in patients with renal insufficiency and antibiotic-associated colitis.

The systemic absorption of orally administered vancomycin was evaluated in five patients (six occasions) with moderate to severe renal insufficiency and documented antibiotic-associated colitis. The patients' ages ranged from 28 to 63 years and weights varied from 50.0 to 76.2 kg. Vancomycin doses were 125 mg (one case), 250 mg (three cases), and 500 mg (two cases) every six hours. Multiple serum concentrations were obtained (range four to 19) during the seven- to 28-day courses of vancomycin therapy. Vancomycin serum concentrations were detectable in five of the six cases as soon as two hours after the first dose, and plateaued within four days. A linear relationship between daily dose and the vancomycin serum concentration was observed (r = .8575, P less than .01). Routine monitoring of vancomycin serum concentrations in adult patients may not be necessary unless high dose (greater than 2 g/d) or prolonged therapy (greater than ten days) is required.