Renal handling of zomepirac sodium (McN-2783-21-98) in the rat.

The plasma and renal clearance of zomepirac, a weak organic acid, was investigated in anesthetized CR Wistar rats after administration of single bolus i.v. injections or continuous i.v. infusions of the 14C-labeled compound. Adjustment of urine pH to the alkaline range caused more than an 8-fold lowering of the plasma elimination half-life (from 7.0 to 0.8 hr) and enhanced renal clearance by a factor of 53 compared to control. Acidification of the urine or probenecid administration increased the elimination half-life (to 10.9 and 17.5 hr, respectively), and decreased renal and plasma clearance of zomepirac. Since zomepirac is highly bound to plasma proteins (approximately 98%), only a small fraction of the drug is available for filtration at the glomerulus. Therefore, the renal elimination of zomepirac is accomplished mainly by active tubular secretion. Passive nonionic reabsorption is a major factor in determining the net clearance of the drug.

Effect of tolmetin on renal function and prostaglandin metabolism.

The effect of tolmetin on prostaglandin synthesis by minces of rat renal medulla and on prostaglandin cyclooxygenase of rabbit renal medulla was determined in vitro. The effect of tolmetin was compared to the effects of indomethacin and ibuprofen. Pretreatment of rats in vivo with tolmetin, indmethacin or ibuprofen reduced prostaglandin synthesis by minces of renal medulla. Incubation of medullary tissue in medium containing tolmetin or indomethacin also decreased prostaglandin production. Both drugs reduced O2 consumption by prostaglandin cyclooxygenase from rabbit renal medulla. In addition, the effect of tolmetin, indomethacin and ibuprofen on renal blood flow and the intrarenal distribution of renal blood flow was measured in anesthetized dogs. Tolmetin and ibuprofen resemble indomethacin in reducing renal blood flow and in shifting the distribution of renal cortical flow from the inner cortex toward the outer cortex. It is concluded that tolmetin is an effective inhibitor of prostaglandin synthesis and affects renal function in a fashion similar to other prostaglandin synthesis inhibitors.

Azolimine: a nonsteroidal antagonist of the effects of mineralocorticoids on renal electrolyte excretion.

Azolimine, CL 90,748, an imidazolidinone, displayed the capacity to antagonize the effects of mineralocorticoids on renal electrolyte excretion in several animal models. Although large doses of azolimine produced natriuresis in adrenalectomized rats in the absence of exogenous mineralocorticoid, its effectiveness was greater in the presence of a steroid agonist. However, in conscious dogs given an infusion of saline plus dextrose, azolimine was only effective when desoxycorticosterone (DCA) was administered. The drug, therefore, may not be a pure competitive antagonist of mineralocorticoid, but its greater efficacy in the presence of mineralocorticoid distinguishes it from noncompetitive mineralocorticoid antagonists as amiloride and triamterene. Azolimine significantly improved the urinary Na/K ratio when used in combination with thiazides, furosemide and other classical diuretics both in adrenalectomized, desoxycorticosterone-treated rats and in sodium-deficient rats.