Protein binding antimicrobial therapy

Nitrofurantoin is administered orally and is rapidly and almost completely absorbed from the small intestine only low levels of activity are achieved in serum because the drug is rapidly metabolized. Relatively high protein binding (about 70%) also affects serum levels, reducing potential for systemic toxicity and alteration of intestinal flora. Relative tissue penetration is much lower than other antimicrobials for UTIs, and therefore, nitrofurantoin is not indicated in the therapy of infections such as pyelonephritis and renal cortical or perinephric abscesses. Nitrofurantoin is rapidly excreted by glomerular filtration and tubular secretion to yield effective urinary levels. In moderate to severe renal dysfunction, toxic blood levels may occur while urinary levels may be inadequate. The drug is inactivated in the liver. 

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