Absorption Distribution and Excretion

Vancomycin is poorly absorbed from the gastrointestinal tract, resulting in high concentrations in the feces. In neutropenic patients and others with altered gastrointestinal mucosa with denudation, significant oral absorption of vancomycin may occur and may be accompanied by additive toxicity if rapid infusion or large parenteral doses of the drug are given concomitantly. Except for the treatment of staphylococcal enterocolitis and pseudomembranous colitis, it is administered intra venously. Peak serum levels are achieved 2 hours after intravenous (IV) administration, and about 55% is bound to serum protein. The therapeutic range is a trough concentration between 5 and 15 ^g/mL, and the peak should stay below 60 ^g/mL to avoid side effects. In normal adults the serum half-life is 5 to 11 hours. With impaired renal function, the half-life is 7 to 9 days. The dose of vancomycin must be carefully adjusted to avoid toxicity or ineffective treatment, especially in patients undergoing hemodialysis. Pediatric oncology patients with normal renal function may require van-comycin dosage regimens that are substantially greater than predicted. Similar studies in adult patients with hematological malignancies have suggested a larger dosage requirement as well, owing to an increased volume of distribution.

After IV administration, vancomycin diffuses into serous cavities and across inflamed but not normal meninges. It can be used in the treatment of meningitis with susceptible organisms. It is also given via ventricu-loatrial or ventriculoperitoneal shunts when these become infected.

Renal excretion is predominant, with 80 to 90% of an administered dose eliminated in 24 hours. Only small amounts appear in the stool and bile after intravenous administration.

Teicoplanin, like vancomycin, is not absorbed from the intestinal tract. Peak plasma levels are achieved about 2 hours after intramuscular administration. The drug distributes widely in tissues; plasma protein binding is about 90%. The half-life approximates 50 hours, which is considerably longer than that of vancomycin, and may make it useful for outpatient administration. Like van-comycin, teicoplanin is excreted by the kidneys.

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