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uricosuric agents


  • Uricosuric agents act directly on renal tubule → incr. uric acid renal excretion;
  • They can also alter plasma binding, distribution & renal excretion of other organic acids;
  • Uric acid in man generally demonstrates net reabsorption in most instances with about 10% of filtered uric acid being excreted, although net secretion is possible;
  • This net reabsorption is via an inhibitable specific transporter which allows luminal uric acid to be exchanged with cellular anions (incl. PAH); The uric acid then exits cell via a different transporter on basolateral membrane not involving PAH;
  • Uricosuric agents when present in lumen, compete with urate for the brush border transporter, thus decr. urate reabsorption;
  • Probenecid also inhibits a specific PAH transporter on basolateral memb. → decr. i/cell. PAH & thus causing decr. PAH secretion;
  • Biphasic effects on urate excretion are usually present depending on the concentration of the uricosuric agent.
    • Low doses usually cause decr. excretion presumably due to extreme sensitivity of urate secretion transporter to these drugs at the lower dose → decr. secretion & no effect on reabs.;
    • Higher doses usually incr. excretion as inhib. reabsorption » inhib. secretion;

Interactions b/n uricosuric agents:

  • one drug may decr. tub. secret. of another drug → decr. luminal [] → decreased inhibition of urate reabsorption.
  • inhib. of urate secretion by one drug may counter the inhib. of reabs. by another;


  • Sulfinpyrazone:
    • Strong organic acid congener of phenylbutazone with more potent uricosuric effect similar to probenecid, but lacks BTZ's anti-inflamm. effect although inhib. platelet function & may induce hypoglycaemia by decr. metabolism of sulfonyureas & also it inhibits metabolism of warfarin;
uricosurics.txt · Last modified: 2011/08/25 11:24 by

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