Preparation and characterization of a sulindac sensor based on PVC/TOA-SUL membrane.

A potentiometric sulindac sensitive sensor based on tetraoctylammonium (Z)-5-fluoro-2-methyl-1-[[p-(methylsulfinyl)phenyl]methylene]-1H-indene-3-acetate (TOA-SUL) was described. The electrode responded with sensitivity of 57.5±1.6mV decade(-1) over the linear range 5×10(-5)-1×10(-2)mol L(-1) at pH6.0-9.0. It had the limit of detection 1.4×10(-5)mol L(-1), a fast response time of 13s and showed clear discrimination of sulindac ions from several inorganic and organic compounds and also amino acids. This electrode did not contain any inner solutions, so it was easy and comfortable to use. The proposed sensor was used to determine sulindac in clear solution and in urine sample solution.

Individual variability in concentrations of urinary sulindac sulfide.

Among 70 patients with arthritis who were receiving satisfactory maintenance therapy with sulindac (300 to 400 mg daily), 64% had no detectable sulindac sulfide (active metabolite) in one to four random urine specimens. However, 36% had 1.0 to 7.8 (mean, 2.2 +/- 1.4) micrograms/ml sulindac sulfide in urine, similar to the therapeutically effective concentrations found in 24 concurrent plasma specimens (1.4 to 9.0 micrograms/ml). Ten patients had sulindac sulfide in only one or two of two to four urine specimens. Thus, 36% of the patients had pharmacodynamically significant concentrations of sulindac sulfide in urine, presumably capable of suppressing the cyclooxygenase pathway responsible for prostaglandin synthesis in the kidney and elsewhere. The findings suggest individual variability in the capacity for renal oxidation of sulindac sulfide to inactive metabolites, perhaps related to genetic or environmental factors or both. These findings may help to explain conflicting reports on the effects of sulindac on urinary prostaglandins and renal function.

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.

Analysis of sulindac and metabolites in plasma and urine by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method with ultraviolet detection is described for the quantification of sulindac, sulindac sulfone and sulindac sulfide in plasma and sulindac, trans-sulindac, sulindac sulfone and sulindac sulfide in urine. Plasma samples are de-proteinized with acetonitrile and urine samples are injected directly following enzymatic hydrolysis of glucuronide metabolites. The resulting chromatograms are essentially free from endogenous interference and the limits of detection are 0.1 microgram/ml for plasma and 0.2 microgram/ml for urine for all of the above compounds.

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.

Analytical methods for the determination of sulindac and metabolites in plasma, urine, bile, and gastric fluid by liquid chromatography using ultraviolet detection.

A high-performance liquid chromatographic method using a linear elution gradient has been developed for the analysis of sulindac, sulindac sulfone, and sulindac sulfide in plasma, urine, bile, and gastric fluid. The methodology uses reverse-phase, radial compression chromatography with gradient elution, and UV detection. Sulindac and its metabolites in plasma can be quantitated at 0.25 microgram/mL with a mean CV of 6.0 +/- 2.9%; urine, bile, and gastric fluid (0.5 microgram/mL) yield a mean CV of 5.5 +/- 1.9%.

Effects of sulindac and indomethacin on renal prostaglandin synthesis.

We compared the effects of sulindac and indomethacin, the effects of two nonsteroidal anti-inflammatory drugs, on renal prostaglandin synthesis and renal function. Sulindac, 200 mg twice daily, indomethacin, 25 mg four times a day, or placebo were taken by 15 normal female subjects (five in each of three treatment groups). Indomethacin decreased renal excretion of prostaglandins PGE2, PGF2 alpha, and 6-keto-PGF1 alpha, but sulindac and placebo had no effect on renal prostaglandin excretion. Concomitant with the reduction of renal prostaglandin synthesis in the indomethacin group, sodium and chloride excretion decreased; sulindac and placebo had no discernible effects on urine electrolytes. Extrarenal cyclooxygenase activity, as assessed by platelet thromboxane beta 2 release, was inhibited by both sulindac and indomethacin. Plasma renin activity and plasma aldosterone levels fell in all groups as a result of positive sodium balance, but the decrements of aldosterone were greater after indomethacin and sulindac. None of the treatments altered glomerular filtration rate or renal plasma flow in these normal women. We conclude that in normal women renal prostaglandin synthesis and prostaglandin-dependent tubular functions such as Na and Cl reabsorption are relatively unaffected by doses of sulindac (200 mg twice daily) that inhibit nonrenal cyclooxygenase. This may reflect the capacity of oxidative enzymes in the kidney to convert the active sulfide metabolite of sulindac to the inactive prodrug sulindac sulfoxide.

Dimethyl sulfoxide inhibits bioactivation of sulindac.

Sulindac, a nonsteroidal anti-inflammatory agent, is converted to a bioactive sulfide metabolite via reversible reduction of its sulfoxide moiety. To test whether DMSO can inhibit conversion of sulindac to its active form, eight healthy men received, in a randomized, crossover manner, 400 mg of sulindac, orally, either alone or 60 min after an oral dose of DMSO (30 ml, 70% solution). After the drug combination, mean plasma concentrations of the sulfide metabolite were significantly lower than in controls at 1.5, 2, 3, 4, and 8 hr after sulindac administration. The mean area under the plasma sulfide concentration-time curve for 0 to 12 hr was 30% (range 7% to 56%) lower after DMSO treatment. This study suggests that DMSO can inhibit metabolism of other sulfoxides in man and may antagonize the therapeutic efficacy of sulindac.

Measurement of sulindac and its metabolites in human plasma and urine by high-performance liquid chromatography.

A sensitive high-performance liquid chromatography assay for simultaneous measurement of sulindac and its major metabolites was developed. The extraction methods provided greater than 89% recovery of sulindac and its sulfone and sulfide metabolites from both plasma and urine. Complete resolution and accurate detection of the three compounds was achieved with a reversed-phase column, UV detection at 254 nm and a methanol-acetate buffer mobile phase. Levels of sulindac and its metabolites were determined in plasma and urine from four volunteers after oral administration of 200 mg Clinoril. Glucuronide conjugates in urine were measured after alkaline hydrolysis.