Metabolism and disposition of phenazopyridine in rat.

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Thomas BH, Whitehouse LW, Solomonraj G, Paul CJ

Metabolism and disposition of phenazopyridine in rat.

Xenobiotica. 1993 Feb;23(2):99-105.

PubMed ID
8498084 [ View in PubMed
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Abstract

1. The blood profile, tissue distribution, biliary and urinary excretion, and metabolism of 14C-phenazopyridine (PAP) was studied in male Wistar rats. 2. Based on the blood profile of 14C the absorption of PAP from the gastrointestinal tract was rapid; the t1/2 of elimination was 7.35 h. 3. Biliary excretion was a major route of elimination with 40.7% dose excreted by this route in bile duct-cannulated rats over the 0-8 h period. The predominant metabolite was conjugated 4'-hydroxy-PAP. 4. Liver and kidney showed the highest tissue levels of PAP-derived 14C, and significant covalent binding was found in these two tissues. 5. The major urinary metabolite of PAP was 4-acetylaminophenol (NAPA) followed in order by 5,4'-dihydroxy-PAP, 5-hydroxy-PAP, 4'-hydroxy-PAP and 2'-hydroxy-PAP; unchanged PAP accounted for < 1% dose. 6. Doubling the dose of PAP to 200 mg/kg caused a proportionate decrease in urinary NAPA excretion and an increase in 5-hydroxy-PAP.

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