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A renal mechanism for the clofibric acid-probenecid interaction
Abstract:
A rabbit model has been used to investigate two hypotheses for the decrease in clofibric acid plasma clearance on probenecid coadministration in man. Rabbits administered probenecid (10 mg/kg followed by 10 mg/kg/hr) showed a mean reduction from control values of 68% for clofibric acid plasma clearance, 80% for clofibric acid glucuronide renal clearance and an elevation in the area under the plasma clofibric acid glucuronide concentration-time curve of 5.2-fold. These findings support the hypotheses that the decrease in clofibric acid plasma clearance involves the inhibition of the renal secretion of clofibric acid glucuronide by probenecid and the subsequent hydrolysis of the glucuronide as the major mechanism, rather than direct inhibition of clofibric acid glucuronide synthesis by probenecid, but do not exclude a mechanism in which both processes operate.
Insights
Probenecid significantly reduces clofibric acid clearance by inhibiting renal secretion of its glucuronide metabolite. This suggests probenecid primarily affects clofibric acid elimination through glucuronide hydrolysis, not synthesis.
Area of Science:
- Pharmacology
- Drug Metabolism
- Renal Physiology
Background:
- Clofibric acid is a lipid-lowering agent.
- Probenecid is known to affect renal drug transport.
- The interaction between clofibric acid and probenecid impacts drug clearance.
Purpose of the Study:
- To investigate the mechanisms behind decreased clofibric acid plasma clearance when coadministered with probenecid.
- To test hypotheses regarding probenecid's effect on clofibric acid glucuronide metabolism and excretion.
Main Methods:
- Utilized a rabbit model to study drug interactions.
- Administered probenecid at specific dosages (10 mg/kg followed by 10 mg/kg/hr).
- Measured clofibric acid plasma clearance and clofibric acid glucuronide renal clearance.
Main Results:
- Probenecid administration reduced clofibric acid plasma clearance by 68%.
- Renal clearance of clofibric acid glucuronide decreased by 80%.
- Area under the plasma glucuronide concentration-time curve increased 5.2-fold.
Conclusions:
- Findings support probenecid inhibiting renal secretion of clofibric acid glucuronide.
- Subsequent hydrolysis of the glucuronide is a major factor in reduced clofibric acid clearance.
- A combined mechanism involving both inhibition and hydrolysis cannot be excluded.