Active Sulfide Metabolite Research Articles

Placental transfer of sulindac, sulindac sulfide, and indomethacin in a human placental perfusion model

Objective: Evaluation of the transplacental transfer and placental metabolism of sulindac, its active sulfide metabolite, and indomethacin, drugs used as tocolytic agents, in dual recirculating human placental perfusion. Study Design: Term placentas were obtained with maternal consent immediately after delivery. Drugs were added to the maternal reservoir, together with antipyrine as a reference compound, and disappearance from the maternal circulation and appearance in the fetal circulation were followed up for 2 hours in 4 experiments for each compound. Drug concentrations were analyzed by high-performance liquid chromatography. Results: The fetal/maternal concentration ratios after 2-hour perfusions were 0.34 ± 0.19 (mean ± SD, sulindac), 0.54 ± 0.17 (sulfide), and 0.45 ± 0.16 (indomethacin), and the fetal-maternal transfer percentages at 2 hours were 11.6 ± 5.9 (sulindac), 18.2 ± 5.2 (sulfide), and 15.3 ± 4.5 (indomethacin). No metabolism of sulindac or indomethacin was detected. Conclusion: Sulindac sulfide, formed through hepatic metabolism, reaches the fetus in higher concentrations than does sulindac or indomethacin. Neither sulindac nor indomethacin is metabolized by the human placenta. (Am J Obstet Gynecol 1999;180:174-80.)

Placental transfer of sulindac and its active sulfide metabolite in humans

OJECTIVE: Our aim was to investigate whether the human placenta is permeableto sulindc or its active sulfide metabolite. STUDY DESIGN: Nine pregnant patients (median gestational age [range]: 31.8 [24.3 to 36.4] weeks) were given a 200 mg oral dose of sulindac 5.5 (4.4. to 6.7) hours before 18 intravascular transfusions for rhesus or Kell alloimmunization. At each procedure maternal and fetal serum levels of sulindac and the active sulfide metabolite were measured by high-performance liquid chromatography. RESULTS: The maternal sulfide level was significantly higher than the fetal sulfide levels, but no significant difference was noted between maternal and fetal sulindac levels. The sulfide fetal/maternal ratio was significantly lower than the sulindac fetal/maternal ratio. The sulfide/sulindac ratio was significantly higher in maternal serum versus fetal serum. The sulfide/sulindac ratio correlated with time from drug ingestion to sampling on the maternal side only. In patients studied on more than one occasion no consistent relationship between fetal sulindac, fetal sulfide, or fetal sulfide/sulindac ratio, and gestational age could be demonstrated. CONCLUSION: The placenta is permeable to sulindac but less so to its active surface metabolite. The reduction of sulindac to its active sulfide metabolite is decreased in the human fetus.

Sulindac and polyp regression.

Sulindac is useful in regression of adenomatous polyps. In addition to orally administered sulindac, rectal preparations also appear to be efficacious [32]. However, further studies are necessary to determine whether regression of adenomas, the precursor of colorectal cancer, will cause decrease in colorectal cancer risk in both FAP and non FAP patients. Moreover, clinical studies are needed to test the application of this potential chemopreventative drug in several other patient populations. Several interesting observations have been made concerning the use of sulindac. Indomethacin, a related NSAID to sulindac, did not cause polyp regression. Also, upper gastrointestinal tract polyps in the stomach and duodenum appear not to be affected by sulindac therapy. These observations might be explained by the metabolism of sulindac in which the pharmacologically active sulfide metabolite is generated and distributed in the large intestine. Also, investigators noted that after discontinuation of sulindac adenomas recurred. Sulindac treatment was well tolerated at the usual clinical doses. Although some investigators have speculated on the effect of prostaglandin inhibition sulindac on cAMP-dependent mechanisms which control cellular proliferation [33], the cause of adenoma regression is unknown. There is evidence that colorectal endogenous prostaglandin levels decrease with sulindac. Evaluation of colorectal mucosal cellular proliferation in patients treated with sulindac has revealed a decrease in labelling index by bromodeoxyuridine labeling in one study [28] but no change in labelling index by [3H]thymidine incorporation in another investigation [34]. Also, ki 67 labelling index, another measure of cellular proliferation, was not affected in the colorectal mucosa of patients taking sulindac.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal toxicity of the nonsteroidal anti-inflammatory drugs.

NSAIDs pose little threat of renal insult in normal, healthy persons at therapeutic dosages. However, NSAID administration to susceptible persons may cause decrements in renal plasma flow and glomerular filtration rate within hours. Such acute noxious renal effects are mediated by products of arachidonic acid metabolism. Precipitous decrements in glomerular filtration and renal ischemia, manifested by increased serum creatinine and urea nitrogen, are possible. However, these effects are usually fully reversible with prompt discontinuation of the offending NSAID. Risk factors for the development of these acute renal effects are known. Acute interstitial nephritis with or without nephrotic syndrome is a rare form of renal toxicity that typically occurs between 2-18 months of use. Renal impairment may be so severe as to require temporary hemodialysis; however, renal function usually returns to normal upon discontinuation of the NSAID. The mechanism of acute interstitial nephritis is presumed to be of allergic origin but could also be caused by a reactive metabolite. Fenoprofen use appears to be associated with a much higher risk for its development. In contrast to the acute effects of NSAIDs, irreversible, analgesic-associated nephropathy manifested by papillary necrosis and chronic interstitial nephritis may occur following months to years of high doses of analgesic mixtures. The mechanism by which combination analgesics produce this form of renal injury is unknown and could be either a result of medullary ischemia or a direct effect of a reactive metabolite. An important issue to be resolved is the relationship between the acute, reversible, prostaglandin-mediated renal effects of the NSAIDs and chronic, irreversible destruction, if such a relationship exists. Theoretically, continual or repeated decrements in renal function in patients with predisposing risk factors could cause or contribute to progressive deterioration in renal function. Elevations in blood pressure or interference with the effects of antihypertensive medications could theoretically also contribute to long-term renal deterioration. In addition to renal syndromes caused by NSAIDs that result in renal impairment, other transient effects on electrolyte and water metabolism may also occur. Reduced secretion of sodium may result in formation of edema, exacerbation of heart failure, or increased blood pressure. Hyporeninemic-hypoaldosteronism may produce hyperkalemia. Finally, reduced excretion of water has rarely caused hyponatremia. It has been suggested that NSAIDs may be renoprotective in patients with nephrotic syndrome. Others have suggested that sulindac is "renal-sparing" because of a unique metabolic pathway that supposedly limits the exposure of the kidney to the active sulfide metabolite.(ABSTRACT TRUNCATED AT 400 WORDS)

Reversible Acute Decrease in Renal Function by NSAIDs in Cirrhosis

The effects of sulindac were compared with those of ibuprofen or naproxen on creatinine clearance and urinary prostanoids in patients with severe alcoholic cirrhosis. Sulindac caused acute declines in all renal parameters in four of five patients. The effect occurred with serum concentrations of the active sulfide metabolite comparable to those in patients with no hepatic impairment. The patient who was not affected had less effects on urinary PGE2 and TxB2 and no effect on 6-keto PGFlα. In this patient, dosing with ibuprofen caused pronounced declines in all urinary prostanoids and a decrease in creatinine clearance. Two other patients treated with ibuprofen and one treated with naproxen also suffered decrements in all parameters. In conclusion, sulindac had suppressant effects on renal prostanoids associated with declines in creatinine clearance in these patients with cirrhosis, indicating a need for similar cautions with its use as with other NSAIDs.

Biotransformation of sulindac in end-stage renal disease.

In normal humans sulindac, a prodrug, undergoes two major biotransformations: irreversible oxidation to the inactive sulfone metabolite and reversible reduction to the pharmacologically active sulfide metabolite. To assess any effect of end-stage renal failure on sulindac biotransformation, six patients were given 200 mg sulindac orally. Plasma was sampled over 24 hours. Protein binding of sulindac and metabolites was determined by equilibrium dialysis. Results were compared with historic controls. AUC(0-12) for sulindac and the sulfone were similar to controls. AUC(0-12) for the sulfide was significantly reduced to 4.85 micrograms X hr/ml from 13.1 micrograms X hr/ml (P less than 0.02). Protein binding of all three compounds was significantly reduced by renal failure. When corrected for protein binding, the AUC(0-12) for sulindac and the sulfone was twice that of controls whereas that of the sulfide was 42 ng X hr/ml compared with 83 ng X hr/ml in normal individuals (P less than 0.001). This suggests that end-stage renal failure impairs the reduction of sulindac to the active sulfide whereas oxidation to the sulfone is intact.

The effects of sulindac and its metabolites on acute stress-induced gastric ulcers in rats

Rats were given a single intragastric administration of the prodrug sulindac (4.0 mg/kg) or its sulfide (1.0, 2.0, 4.0, or 8.0 mg/kg) or sulfone (1.0, 2.0, 4.0, or 8.0 mg/kg) metabolites and were then subjected to acute stress in the form of immobilization for 3 hr in a cold environment. Control rats received an equal volume of propylene glycol vehicle or nothing po. Other rats received 200 mg/kg acetylsalicylic acid (ASA) with or without stress, to compare the gastrointestinal effects of sulindac metabolites with those of a known non-steroidal anti-inflammatory agent. The sulfide metabolite exacerbated stress-induced gastric glandular ulcer incidence and severity in a dose-related manner relative to all groups except the ASA-stress group, which exhibited the greatest amount of gastric damage. The sulfone metabolite did not potentiate ulcer incidence or severity beyond control (stress only) levels at lower doses. However, at 4.0 and 8.0 mg/kg, the observed ulceration was greater than that seen in stressed but otherwise untreated animals. Sulindac, vehicle, and otherwise untreated rats exhibited a similar degree of stress-induced gastric damage. It appears that the prodrug does not significantly enhance stress-related gut disease, but that the active sulfide metabolite does. Although the clinical literature suggests that the sulfone metabolite is inactive, the present results suggest otherwise. While this metabolite did not, by itself, induce gastric damage at higher doses, sulfone did exacerbate stress ulcer formation. This is the only report of which we are aware, indicating a possible toxic effect of the sulfone metabolite.

Effects of sulindac and ibuprofen in patients with cirrhosis and ascites: An explanation for the renal-sparing effect of sulindac

Nonsteroidal antiinflammatory drugs impair renal function in susceptible patients with cirrhosis and ascites. A new antiinflammatory drug, sulindac, is reported not to affect renal function. To evaluate its renal-sparing mechanism, sulindac was administered for 5 days and ibuprofen for 1 day to 10 patients and paraaminohippurate and inulin clearances, serum and urine eicosanoids, and serum and urine sulindac metabolites were monitored. Ibuprofen reduced renal clearances in the 5 subjects with greatest sodium retention, whereas sulindac had no effect. Plasma concentration of the active sulfide metabolite was markedly increased in liver patients, and this concentration correlated with the inhibition of serum thromboxane (r = 0.75, p = 0.01). The percent inhibition of serum thromboxane with sulindac administration correlated with the inhibition of urinary eicosanoids (r = 0.68–0.81, all p < 0.02). Ibuprofen was generally a more potent inhibitor of serum and urine eicosanoids. Thus, a major factor in the renal-sparing effect of sulindac appears to be its less potent inhibition of renal and extrarenal cyclooxygenase systems.

Sulindac metabolism: the importance of an intact colon.

The pharmacokinetics of sulindac have been studied after a single 200 mg oral dose in six normal subjects and five patients with surgical ileostomies. The plasma concentration-time curves for sulindac were similar in both groups up to 12 hours after dosing, indicating similar absorption of the drug. Higher plasma concentrations of sulindac were found in normal subjects after 12 hours, but this late phase accounted for only 12% of the total AUC in the subjects. The sulfone metabolite showed a similar pattern, with no statistically significant difference in the total AUC, but in patients with ileostomy there was a halving of the AUC after 12 hours. Plasma concentrations of the active sulfide metabolite were similar in both groups up to 12 hours, but negligible concentrations were detected in the plasma of patients with ileostomy after 12 hours. Thus the AUC after 12 hours, which represented 55% of the total AUC in normal subjects, was reduced to only 7% in patients with ileostomy. The rate of reduction of sulindac in vitro by ileostomy effluent was only one hundredth that by normal feces. Our results suggest that the gut microflora are an important site of reduction of sulindac in man. Comparison of AUC values suggests that about half the total sulfide is formed by the gut bacteria, probably from sulindac excreted in the bile.

Effects of age and disease on the pharmacokinetics and pharmacodynamics of sulindac.

The disposition and effect on hemostasis of a single 150 mg dose of sulindac was studied in young healthy subjects and in older patients with arthritis. Older patients were restudied after 2 weeks of sulindac, 150 mg b.i.d. The only difference in disposition of the first dose was a reduced plasma sulfone metabolite concentration in the elderly patients with arthritis. Chronic sulindac dosing resulted in accumulation of the drug and its sulfone and sulfide metabolites in plasma to a greater extent than previously reported for young subjects. No differences in renal clearance of sulindac and its sulfone metabolite related to age or chronic drug dosing were observed. No renal excretion of the active sulfide metabolite was detected. Bleeding time in the elderly patients was shorter than in the young healthy subjects before sulindac dosing, but was prolonged in the elderly patients after 2 weeks of dosing to values similar to control data from the young healthy subjects. This change correlated weakly with plasma sulfide metabolite concentrations. Differences in bleeding time were not reflected in changes in platelet aggregation induced by adenosine diphosphate either with respect to age or chronic drug dosing. Our data provide no justification for lowering the recommended dose of sulindac for patients older than 65 years of age.

Biliary secretion of sulindac and metabolites in man.

The biliary secretion of sulindac and metabolites after a single 400 mg oral dose of the drug was studied in 3 elective gallbladder surgical patients following placement of an occludable T-tube in the common bile duct. Bile and systemic plasma were sampled at frequent intervals for up to 36 h postdose. The apparent biliary clearance (Vcl,bile) of the prodrug sulindac is about 25 times greater than that of the pharmacologically active sulfide metabolite. The total biliary flux of drug in normal man with an uninterrupted enterohepatic cycle, calculated from Vcl,bile and historic mean plasma drug AUCinfinity0 values, averages 144 and 12.2 per cent of the dose as sulindac and the sulfide metabolite, respectively. Thus, enterohepatic recycling of the drug in man is principally in the form of the prodrug which not only limits exposure of the intestine to the active moiety but also sustains systemic concentrations of active drug upon reabsorption of the prodrug.

ChemInform Abstract: MEMBRANE EFFECTS OF ANTIINFLAMMATORY AGENTS. 1. INTERACTION OF SULINDAC AND ITS METABOLITES WITH PHOSPHOLIPID MEMBRANE, A MAGNETIC RESONANCE STUDY

AbstractDie Wechselwirkungen mit Phospholipidmembranen sind beiSulindac (Ia) und dem Metaboliten (Ic) schwach, jedoch bei (Ib) stark.

Membrane effects of antiinflammatory agents. 2. Interaction of nonsteroidal antiinflammatory drugs with liposome and purple membranes

The interaction of the nonsteroidal antiinflammatory drugs (NSAIDS) indomethacin, diflunisal, and flurbiprofen and the active sulfide metabolite of sulindac with phosphatidylcholine (PC) liposomes was investigated using differential scanning calorimetry (DSC). These biologically active structures decrease the phase transition temperature and broaden the transition peak with increasing concentration, but without affecting the enthalpy change for the transition on the thermal scan. A comparison with the effects of the prodrug sulindac and its inactive sulfone metabolite suggests that the main action of NSAIDS on membranes is a reduction of the cooperative interaction between phospholipid molecules. The probable positions of these compounds in the bilayer are inferred from similar DSC effects of several reference compounds whose mode of binding to the PC bilayer have previously been described. The active antiinflammatory structures appear to insert deeply into the hydrocarbon region of the bilayer, whereas the inactive compounds probably bind mainly to the carbonyl region near the surface. Using purple membrane as a model to study the drug effect on protein--protein interaction in this membrane system, low concentrations of active NSAIDS effectively dissociate the bacteriorhodopsin lattice. These results suggest that the active NSAIDS studied here are able to partition deeply into the hydrocarbon region of the bilayer and interact with a membrane protein imbedded inside the bilayer. The prodrug sulindac per se is devoid of any significant membrane effects.

The disposition of sulindac

The disposition of sulindac, a new nonsteroid anti-inflammatory drug, has been studied in normal volunteers in five separate clinical studies. Based upon material balance considerations, a minimum of approximately 88% of an oral dose is absorbed. The major biotransformations involve irreversible oxidation of the sulfinyl group of sulindac to sulfone and reduction to the corresponding sulfide. The latter, which all available evidence indicates to be the pharmacologically active form of sulindac, is not excreted in urine, and has an apparent terminal half-life of 18.2 hr, well suited to twice daily dosage of its pro-drug. Following twice daily dosage of sulindac for 5 days, plasma levels of sulfide approach an apparent steady state with concentrations varying only within a twofold range over each dosage interval. The reversible biotransformation between sulindac and its active sulfide metabolite provides the basis for two therapeutic advantages relating to the gastrointestinal intolerance usually associated with anti-inflammatory drugs: (1) circumvention of initial exposure of gastric and small intestinal mucosa to the active form of the drug and (2) maintenance of systemic levels of active drug by means of enterohepatic recycling, principally of inactive pro-drug.