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The metabolic fate of 5-aminosalicylic acid (reported to be the active therapeutic moiety of sulfasalazine) was assessed in fasting rats as a function of dose (25-200 mg/kg) and administration route (oral, intraperitoneal, and intravenous). 5-Aminosalicylic acid is subject to both capacity-limited presystemic (apparently during first passage through the intestinal epithelium) and systemic acetylation. The possibility exists that 5-aminosalicylic acid also is acetylated presystemically after oral sulfasalazine administration to patients with inflammatory bowel disease. Any alteration in the absorption activity if N-acetyl-5-aminosalicylic acid is inactive or less active than 5-amino-salicylic acid.
Sulfapyridine (SP) and 5-aminosalicylic acid (5-ASA) are the two primary metabolites of the anti-inflammatory drug salicylazosulfapyridine (SASP). These two metabolites were studied for induction of chromosomal damage in mammalian cells, in vitro and in vivo, in an attempt to understand better the genetic effects produced by SASP in humans and laboratory mice. To this end, SP and 5-ASA were tested for induction of sister-chromatid exchanges (SCE) and chromosomal aberrations (Abs) in Chinese hamster ovary (CHO) cells in vitro. In addition, they were tested in vivo for induction of micronuclei (MN) in mouse bone marrow polychromatic erythrocytes (PCE). SP gave positive results in the in vitro SCE test and the in vivo MN test, and negative results in the in vitro Abs test. 5-ASA was negative in all three tests. These results indicate that it is the SP metabolite of SASP that is necessary for the induction of chromosomal damage reported to occur in humans and mice after treatment with SASP.
p-Aminosalicylic acid, which exists in four ionic forms and whose decarboxylation is well known, was used as a model drug to investigate the effects of surfactants with different charges on its stability. The greatest reduction in the rate of decarboxylation at 50 degrees C occurred when the charge on the micelles was opposite to that of the charge on the drug or when both the drug and the micelle had a neutral charge. Thus, at the highest surfactant concentration, 3 or 5% (w/v), there was a 59% reduction in the rate at pH 2.68 in the presence of the nonionic surfactant polyoxyethylene 24 monocetyl ether, 69% reduction in the rate at pH 4.88 in the presence of the cationic surfactant hexadecyl trimethylammonium bromide, and a 43% reduction at pH 1.01 in the presence of the anionic surfactant sodium cetyl sulfate. The decrease in the rate of decarboxylation was attributed to the partitioning of the drug into the micelles, which provided a phase for improved stabilization. Partition coefficients and rate constants for decarboxylation of the drug inside the micelles were calculated.
A simple synthetic route for the preparation of amino acid conjugate of 5-aminosalicylic acid (5-ASA) was exploited and prepared 5-aminosalicyl-glycine (5-ASA-Gly) in good yield. In vitro and in vivo properties of 5-ASA-Gly as a colon-specific prodrug of 5-ASA were investigated using rats as the test animal. Incubation of 5-ASA-Gly with cecal or colonic contents at 37 degrees C released 5-ASA in 65 or 27% of the dose in 8 h, respectively. No 5-ASA was detected from the incubation of 5-ASA-Gly with the homogenates of stomach or small intestine. Plasma concentration of 5-ASA-Gly decreased rapidly after intravenous administration of 5-ASA-Gly, and no 5-ASA was detected in the blood, which indicated 5-ASA-Gly was not degraded in the plasma. After oral administration of 5-ASA-Gly, about 50% of the administered dose was recovered as 5-ASA and N-acetyl-ASA and 3% as 5-ASA-Gly from feces and 14% as 5-ASA-Gly and 28% as 5-ASA and N-acetyl-ASA from urine in 24 h. These results suggested that a large fraction of 5-ASA-Gly was delivered to the large intestine and activated to liberate 5-ASA. For comparison, total recovery of 5-ASA and N-acetyl-5-ASA from feces after oral administration of 5-ASA-Gly was greater than that from sulfasalazine, which is one of the most commonly prescribed prodrugs of 5-ASA.
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Suppositories of sulphapyridine, 5-aminosalicylic acid, and placebo were used in 45 patients with idiopathic proctitis to determine the active part of sulphasalazine. Each patient used one of the suppositories twice daily for four weeks in a double-blind controlled trial. Complete clinical remission with normal rectal mucosa on sigmoidoscopy occurred in 60% of patients given 5-aminosalicylic acid, but in only 13% and 27% of those given sulphapyridine and placebo respectively. Twelve patients were included twice. In eight of these patients 5-aminosalicylic acid was given one time and sulphapyridine (two patients) or placebo (six patients) another time. Clinical remission occurred in each patient with 5-aminosalicylic acid, but in only one patient during other therapy. The results suggest that 5-aminosalicylic acid is the active therapeutic moiety of sulphasalazine.
BACKGROUND AND AIMS: 5-Aminosalicylate is the gold standard for inducing remission in patients with mildly to moderately active ulcerative colitis. The optimal dose is as yet not defined. Despite some recent developments, the ideal formulation for 5-aminosalicylic acid is still awaited. A new pellet preparation was designed combining slow and delayed release properties. Aims of the study were to find the optimal dose and to test efficacy and safety of a new 5-aminosalicylic acid formulation. METHODS: Three hundred twenty-one patients were included in a double-blind multicenter trial. Inclusion criteria were active ulcerative colitis (Clinical Activity Index [CAI] and Endoscopic Index [EI] according to Rachmilewitz, CAI 6-12; EI >/=4). Three different doses of 5-aminosalicylic acid (0.5 g 3 times a day, 1.0 g 3 times a day, and 1.5 g 3 times a day) were studied for 8 weeks. RESULTS: Clinical remission rate (CAI </=4) was highest in the 1.0 g 3 times a day group (66 %), 50% in the 0.5 g 3 times a day group, and 55% in the 1.5 g 3 times a day group. Hierarchical testing showed no significance, indicating a lack of dose response across the 3 mesalamine doses. In addition, times to first clinical response were similar: 26.5 days (1.0 g 3 times a day), 27.5 days (0.5 g 3 times a day), and 21.5 days (1.5 g 3 times a day). Endoscopic improvement was better with 1.0 g mesalamine 3 times a day than with 0.5 g 3 times a day, but overall endoscopic and histologic improvement was not different between treatment groups. Baseline activity, duration, and localization of ulcerative colitis did have some influence on the therapeutic activity, but there was no significant interaction with the dose of the study drug. Safety, with special focus on kidney function, was excellent in all 3 groups. CONCLUSIONS: There is no significant dose response between mesalamine 1.5 g/day, 3.0 g/day, and 4.5 g/day. The optimal dose to induce remission of ulcerative colitis is 0.5 g 5-aminosalicylic acid 3 times a day. Patients failing with this dose may benefit from an increase of the dose up to 1.0 g 3 times a day, but should also be considered for alternative treatment. A newly developed pellet formulation of 5-aminosalicylic acid has promising efficacy and excellent safety.
The glycoprotein alpha 1-proteinase inhibitor is the specific inhibitor of neutrophil elastase, a major tissue-damaging protease. When incubated with activated neutrophils, alpha 1-proteinase inhibitor lost its pancreatic porcine elastase inhibitory capacity and became incapable of forming a sodium dodecyl sulphate-stable complex with pancreatic porcine elastase. Inhibitors and scavengers of neutrophil-derived reactive oxygen species outlined the crucial role of hypochlorous acid in the alpha 1-proteinase inhibitor inactivation. Moreover, the drug 5-aminosalicylic acid prevented the inactivation of alpha 1-proteinase inhibitor by neutrophils in a dose-dependent manner. Finally, when the capacity of 5-aminosalicylic acid to rescue alpha 1-proteinase inhibitor from the neutrophil-derived attack was plotted as a function of the 5-aminosalicylic acid ability to scavenge neutrophil-derived hypochlorous acid, a positive linear relationship was found. Thus, our results provide a direct evidence that 5-aminosalicylic acid is able to prevent the oxidative inactivation of alpha 1-proteinase inhibitor by neutrophils. Therefore, we suggest that the drug has the potential to limit the elastase-mediated damage of colonic connective tissue by creating a microenvironment of active alpha 1-proteinase inhibitor around the neutrophils.
Sixty patients who had presented recently with a relapse of mild to moderate ulcerative colitis with rectosigmoid involvement were randomly assigned to treatment with either 5-aminosalicylic acid enemas (N = 29) or oral sulfasalazine (N = 31). All patients were in remission, which was documented by clinical, histologic, and endoscopic criteria. Five-aminosalicylic acid treatment was administered on an intermittent schedule, consisting of 4 gm daily for the first seven days of each month; sulfasalazine was given as continuous therapy (2 gm daily as oral tablets). The study period was 2 years. Overall, 9 relapses occurred in the 5-aminosalicylic acid group and 12 occurred in the sulfasalazine group. The actuarial relapse rate at 12 months was 20 percent in the 5-aminosalicylic acid group and 24 percent in the sulfasalazine group; at 24 months, these rates were 37 and 43 percent, respectively. The actuarial relapse curves of the two groups were very similar. The relapse severity was also similar between the two groups. These results show that the authors proposed schedule of maintenance treatment with high-dose 5-aminosalicylic acid enemas is effective in subjects with rectosigmoiditis. This form of intermittent therapy may therefore be proposed for maintaining remission in patients who are refractory to oral and/or rectal treatment with sulfasalazine and steroids or who are intolerant or allergic to sulfasalazine. Treatment with 5-aminosalicylic acid enemas for seven days each month can also constitute an alternative for patients who favor the intermittent schedule over the classic continuous regimen of oral administrations.
The rate of decarboxylation of p-aminosalicylic acid (1) in aqueous solutions was studied at 25 degrees C (mu = 0.5) as a function of pH and buffer concentration. A pH-rate profile was generated by using the rate constants extrapolated to zero buffer concentration. The profile was bell-shaped, with the maximum rate of decarboxylation near the isoelectric pH. The rate constants obtained in buffered solutions indicated general acid catalysis. Bronsted behavior appeared to be adhered to. The two ionization constants of 1 were determined spectrophotometrically at 25 degrees C and at an ionic strength of 0.5. An HPLC method was used to characterize the degradation products of the reaction. Kinetic solvent deuterium isotope effects were studied to further confirm the mechanism of decarboxylation. Below pH 7.0, the mechanism of 1 decarboxylation is the rate controlling proton attack on the carbon-alpha to the carboxylic acid group of 1 anion and the ampholyte, followed by the rapid decarboxylation of the formed intermediate.
In search of new therapies in IBD, the introduction of 4-aminosalicylic acid (4-ASA) has been proposed based on the longstanding, positive clinical experience in tuberculosis, the expected similar modes of action due to the close structural analogy to 5-aminosalicylic acid (5-ASA), an established therapy in IBD, and its inexpensiveness. To better understand the mechanisms of action of aminosalicylates, the intestinal inflammatory response and to develop new, more effective and cost saving drugs it is important to compare 4-ASA with 5-ASA with respect to their pharmacology, mechanisms of action and clinical efficacy. The inhibition of the upregulation of the initial local immune response, the inhibition of the production of inflammatory mediators, e.g. leukotrienes and the direct scavenging of toxic oxygen metabolites are important common antiinflammatory mechanisms. As the clinical experience with 4-ASA is promising, but still limited, 4-ASA currently cannot yet be recommended outside clinical trials. As the costs of 4-ASA are significantly lower compared to 5-ASA, 4-ASA may replace 5-ASA in the near future provided further trials will confirm the therapeutic and pharmacologic equivalency.
The solution degradation of the antiinflammatory agent 5-aminosalicylic acid (5-ASA) was investigated in order to elucidate a mechanism for degradation. Two degradation pathways were considered: decarboxylation by analogy to 4-aminosalicylic acid (4-ASA) decomposition and oxidation from consideration of 5-ASA's aromatic ring substitution pattern (i.e., relation to p-aminophenol). The oxidation of 5-ASA was investigated using cyclic voltammetry and flow electrolysis. These studies showed that 5-ASA is more easily oxidized than is 4-ASA and that 5-ASA undergoes a two-electron, two-proton oxidation consistent with formation of 5-ASA-quinoneimine (5-ASA-QI). This oxidation is followed by subsequent complex chemistry. The decomposition of 5-ASA in solution was examined under a variety of conditions. 5-ASA decomposes most rapidly under conditions promoting oxidation and is most stable under conditions tending to inhibit oxidation. Decarboxylation was not found to be a significant degradation pathway.
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BACKGROUND AND AIMS: There are limited evidence based data concerning the use of azathioprine in ulcerative colitis. We aimed to compare the efficacy of azathioprine and oral 5-aminosalicylic acid in inducing remission of steroid dependent ulcerative colitis. METHODS: Seventy two patients with steroid dependent ulcerative colitis were admitted to this investigator-blind study. Steroid dependence was defined as a requirement for steroid therapy > or =10 mg/day during the preceding six months, with at least two attempts to discontinue the medication. The disease had to be clinically and endoscopically active at study entry, and all patients were taking systemic prednisolone (40 mg/day). Patients were randomised to receive azathioprine 2 mg/kg/day or oral 5-aminosalicylic acid 3.2 g/day, for a six month follow up period. The outcome of the treatment was defined as (1) success, indicating induction of clinical and endoscopic remission and steroid discontinuation, or (2) failure, indicating the absence of clinical and endoscopic remission and therefore the need for at least one further cycle of systemic steroids to control symptoms, apart from the initial one, or colectomy. RESULTS: Significantly more patients in the azathioprine than in the 5-aminosalicylic acid group had clinical and endoscopic remission, and discontinued steroid therapy, both in the intention to treat (azathioprine v 5-aminosalicylic acid: 19/36 patients (53%) v 7/36 (21%); odds ratio (OR) 4.78 (95% confidence interval (CI) 1.57-14.5)) and per protocol (azathioprine v 5-aminosalicylic acid: 19/33 patients (58%) v 7/34 (21%); OR 5.26 (95% CI 1.59-18.1)) analysis. CONCLUSIONS: Azathioprine is significantly more effective than 5-aminosalicylic acid in inducing clinical and endoscopic remission and avoiding steroid requirement in the treatment of steroid dependent ulcerative colitis.