The effect of 5-aminosalicylic acid-containing drugs on sulfide production by sulfate-reducing and amino acid-fermenting bacteria

The toxic, bacterial metabolite sulfide is implicated in ulcerative colitis. Ulcerative colitis patients taking 5-aminosalicylic acid-containing drugs have lower fecal sulfide levels than those not taking these drugs. The effects of sulfasalazine, balsalazide, olsalazine, and 5-aminosalicylic acid on sulfide production were studied in a three-stage chemostat pulsed on days 1 to 3 with 5 g sulfasalazine (40 mM) and in pure cultures of amino acid-fermenting and sulfate-reducing bacteria. By the third day of sulfasalazine addition to the chemostat, sulfide concentrations in vessels 1 through 3 had dropped from 1.73, 1.78, and 1.43 mM to 0.01, 0.15, and 0.9 mM, respectively. In pure cultures, 50% inhibition of sulfide production from amino acids occurred at 2.5 +/- 0.05 mM for sulfasalazine, 5 +/- 0.2 mM for olsalazine, 6 +/- 1 mM for balsalazide, and more than 20 mM for 5-aminosalicylic acid. Fifty percent inhibition of sulfide production from sulfate occurred at 0.25 +/- 0.05 mM for sulfasalazine, 0.7 +/- 0.2 mM for balsalazide, and 9.0 +/- 1.0 mM for 5-aminosalicylic acid. The order of effectiveness of equimolar concentrations of drugs (most effective first) in this assay was sulfasalazine, then olsalazine (though given clinically at half the dose of other 5-aminosalicylic acid prodrugs) and balsalazide, and lastly 5-aminosalicylic acid. Inhibition of sulfide production by 5-aminosalicylic acid-containing drugs may contribute to their therapeutic effect in ulcerative colitis.     

Longterm olsalazine treatment: pharmacokinetics, tolerance and effects on local eicosanoid formation in ulcerative colitis and Crohn's colitis.

To examine pharmacokinetics and tolerance of long term administration of olsalazine (azodisalicylate), increasing doses of the drug were given for one year to 31 patients with ulcerative colitis (UC) and nine patients with Crohn's colitis (CC), refractory to, or intolerant of sulphasalazine, until sustained remission was obtained or a maximum of 4 g/day was reached. Colonic drug metabolism was studied by equilibrium in vivo dialysis of faeces. Complete azoreduction occurred in most cases. Concentrations of 5-aminosalicylic acid, but not N-acetyl-5-aminosalicylic acid, in faecal dialysates increased dose dependently. Serum concentrations disclosed no cumulation in the long term and olsalazine was well tolerated, although loose stools occurred transiently in some patients with extensive disease: this was associated with a larger proportion of unsplit olsalazine in the faecal dialysates. Patients with ulcerative colitis having a high prostaglandin E2 concentration (greater than ng/ml) determined by equilibrium dialysis of rectum, were less likely to benefit from treatment. Olsalazine is a very effective means of delivery of 5-aminosalicylic acid to the colonic mucosa in active disease. Use of the drug in controlled trials may be considered safe even in prolonged high dosage.     

The short- and long-term safety of 5-aminosalicylate products in the treatment of ulcerative colitis

5-aminosalicylic acid agents are effective in the treatment of ulcerative colitis. Balsalazide, mesalamine, and olsalazine are alternative formulations to sulfasalazine for the delivery of 5-aminosalicylic acid. The newer compounds might be better tolerated than sulfasalazine in some patients, as long as the intolerance is not due to hypersensitivity to 5-aminosalicylic acid. Adverse events requiring the withdrawal of therapy seem to occur less frequently with balsalazide, mesalamine, and olsalazine compared with sulfasalazine. If patients are unable to tolerate any one of these three 5-aminosalicylic acid-releasing preparations, they might be able to tolerate one of the others, as long as the intolerance is not due to hypersensitivity to 5-aminosalicylic acid.     

Olsalazine versus placebo in the treatment of mild to moderate ulcerative colitis: a randomised double blind trial.

The effect of olsalazine, an analogue of sulphasalazine, consisting of two molecules 5-aminosalicylic acid linked by an azobond has been investigated for the treatment of ulcerative colitis. In a randomised double blind trial we compared 2 g olsalazine with placebo for four weeks. Of the 105 patients, with mild to moderate ulcerative colitis, entered in the trial 52 received olsalazine, and 53 placebo. Treatment had to be terminated prematurely because of untoward effects of olsalazine (mainly diarrhoea) in three patients and treatment failure--that is, increased rectal bleeding in four patients (olsalazine group: one placebo group: three). After four weeks' treatment, a statistically significant improvement in the endoscopic findings in rectum and a positive trend in the reduction of rectal mucus and blood discharge was observed in the patients treated with olsalazine. No statistically significant difference was found for other factors, including stool frequency, consistency, urge to defecate, abdominal pain, and biopsy findings. A comparison between these clinical and endoscopic parameters at study entry and those at study completion (within drug evaluation) showed significant improvement in six of 10 parameters during treatment with olsalazine and in two of 10 during placebo treatment. This difference suggests the significant effect of olsalazine. We conclude that 2 g olsalazine was tolerated as well as placebo, apart from causing diarrhoea in some patients and was slightly superior to placebo during four weeks' treatment of mild to moderate ulcerative colitis. A study with 3 or 4 g olsalazine per day may show a more definite effect.     

Intestinal luminal pH in inflammatory bowel disease: possible determinants and implications for therapy with aminosalicylates and other drugs

Measurements of luminal pH in the normal gastrointestinal tract have shown a progressive increase in pH from the duodenum to the terminal ileum, a decrease in the caecum, and then a slow rise along the colon to the rectum. Some data in patients with ulcerative colitis suggest a substantial reduction below normal values in the right colon, while limited results in Crohn's disease have been contradictory. Determinants of luminal pH in the colon include mucosal bicarbonate and lactate production, bacterial fermentation of carbohydrates and mucosal absorption of short chain fatty acids, and possibly intestinal transit. Alterations in these factors, as a result of mucosal disease and changes in diet, are likely to explain abnormal pH measurements in inflammatory bowel disease (IBD). It is conceivable that reduced intracolonic pH in active ulcerative colitis impairs bioavailability of 5-aminosalicylic acid from pH dependent release formulations (Asacol, Salofalk) and those requiring cleavage by bacterial azo reductase (sulphasalazine, olsalazine, balsalazide), but further pharmacokinetic studies are needed to confirm this possibility. Reports that balsalazide and olsalazine may be more efficacious in active and quiescent ulcerative colitis, respectively, than Asacol suggest that low pH may be a more critical factor in patients taking directly pH dependent release than azo bonded preparations. Reduced intracolonic pH also needs to be considered in the development of pH dependent colonic release formulations of budesonide and azathioprine for use in ulcerative and Crohn's colitis. This paper reviews methods for measuring gut pH, its changes in IBD, and how these may influence current and future therapies.     

Effects of sulphasalazine and disodium azodisalicylate on colonic PGE2 concentrations determined by equilibrium in vivo dialysis of faeces in patients with ulcerative colitis and healthy controls.

The role of arachidonic acid metabolites and the mode of action of 5-aminosalicylic acid, the active moiety of sulphasalazine and disodium azodisalicylate, in ulcerative colitis remain obscure. Therefore, experiments were performed in which the effects of medication on immunoreactive prostaglandin (PG) E2 concentrations in free faecal water were assessed using the equilibrium in vivo dialysis of faeces. Colonic PGE2 concentrations in patients with active ulcerative colitis (n = 11) ranged from 2035-18,000 pg/ml to be compared with a range of 103-188 pg/ml in healthy volunteers (n = 10; p less than 0.001). In all healthy volunteers PGE2 concentrations decreased slightly (p less than 0.05) after disodium azodisalicylate intake 2 g/day, whereas low dose disodium azodisalicylate (0.25 g/day) caused no change. In patients with ulcerative colitis in complete clinical, sigmoidoscopic, and histologic remission withdrawal of sulphasalazine (2 g/day; n = 6) increased PGE2 concentrations to values above normal levels (p less than 0.05) which returned to pretrial values (p less than 0.05) on disodium azodisalicylate (2 g/day; n = 7). In conclusion, increased PGE2 in free faecal water indicates an abnormality in the colonic mucosa, even in the absence of conventional signs of inflammation. We could not confirm the hypothesis that sulphasalazine and 5-aminosalicylic acid exert their therapeutic effect through promotion of endogenous cytoprotective prostaglandins. In contrast, the observation that raised PGE2 concentrations were normalised by disodium azodisalicylate in patients with inactive ulcerative colitis suggests that subclinical disease activity was decreased by 5-aminosalicylic acid.     

Clinical experience of the tolerance of mesalazine and olsalazine in patients intolerant of sulphasalazine

We assessed the tolerance and safety of two new preparations designed to release 5-aminosalicylic acid in the colon in patients with ulcerative colitis who were intolerant of sulphasalazine. Twenty-eight of 37 patients (76%) given mesalazine and 18 of 21 patients (86%) given olsalazine tolerated the new preparations with no adverse effects. No haematologic or biochemical abnormalities were detected. Adverse reactions to the new preparations were usually but not always similar to those they had previously encountered with sulphasalazine, but a few patients experienced rash and diarrhoea. In some patients intolerant of one of the new preparations, their tolerance of the other was assessed. Three patients intolerant of mesalazine tolerated olsalazine. Similarly, three other patients intolerant of olsalazine tolerated mesalazine. We conclude that not all adverse effects of sulphasalazine are due to the sulphapyridine part of the molecule. Some are due to the released 5-aminosalicylic acid and some to the parent compound. Both drugs are likely to prove useful in the management of patients intolerant of sulphasalazine.     

Disposition of 5-aminosalicylic acid by olsalazine and three mesalazine preparations in patients with ulcerative colitis: comparison of intraluminal colonic concentrations, serum values, and urinary excretion.

To compare the disposition of 5-aminosalicylic acid (5-ASA) and its acetylated metabolite during treatment with olsalazine and mesalazine, 14 patients with inactive ulcerative colitis were randomly assigned to olsalazine (1 g twice daily) and the mesalazines, Asacol (800 + 400 + 800 mg daily), Pentasa (750 + 500 + 750 mg daily), and Salofalk (750 + 500 + 750 mg daily) in a crossover design trial so that all received each drug for seven days. Intraluminal colonic concentrations of 5-ASA were estimated after five days by the method of equilibrium in vivo dialysis of faeces. A predose serum sample and a 24 hour urine collection were obtained on day seven. The 5-ASA and acetyl-5-aminosalicylic acid (Ac-5-ASA) values were determined by high performance liquid chromatography. Olsalazine almost doubled the colonic concentrations (mean 23.7 (SEM) (1.9) mmol/l) of its therapeutically active ingredient (5-ASA) compared with equimolar doses of Pentasa (12.6 (2.2) mmol/l; p less than 0.0003) and Salofalk (15.0 (2.0) mmol/l; p less than 0.003). At the same time, olsalazine treatment was associated with lower serum concentrations and urinary excretions (p less than 0.05) of 5-ASA and Ac-5-ASA compared with the mesalazine preparations. The low systemic load of 5-ASA provided by olsalazine reduces the potential risk of nephrotoxicity during long term treatment.     

The optimal dose of 5-aminosalicylic acid in active ulcerative colitis: a dose-finding study with newly developed mesalamine.

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 相似文献   

Oral 5-ASA therapy in ulcerative colitis: what are the implications of the new formulations?

5-aminosalicylic acid (5-ASA) is the standard first-line treatment for mild-to-moderate ulcerative colitis. A variety of 5-ASA delivery systems are available and in development, including both oral and rectal formulations; all of which aim to deliver the active drug to the colon while minimizing systemic absorption. Because the efficacy of most oral 5-ASA therapies is broadly similar, the appropriate selection of a given formulation often relies on other factors. This article explores the differences between oral 5-ASA formulations in terms of their delivery system, reviews the available data on oral 5-ASA treatment efficacy and tolerability, and examines the rationale for changing from one 5-ASA formulation to another if a patient does not respond to, or worsens on, their existing agent.     

Olsalazine-related diarrhoea: does rat intestine adapt in vivo?

Diarrhoea may occur in up to 10% of patients with ulcerative colitis treated with olsalazine, the azolinked dimer of 5-aminosalicylic acid. However, this symptom often disappears despite continued drug medication. To examine reversibility of and adaptation to olsalazine effects on intestinal absorption, rats were fed olsalazine (4 mg/100 g body weight/day) for 0 (controls), 12, 24, and 32 days. Jejunal, ileal, and colonic loops were perfused in situ with buffer or olsalazine (11.6 mM) in a pendular perfusion system. Water and electrolyte absorption was inhibited in all intestinal segments (p less than 0.001). In the proximal small intestine, however, sodium absorption was inhibited by 61%, whereas chloride and potassium absorptions were turned into net secretion. In contrast, in ileal and colonic segments sodium, chloride, and potassium absorptions were turned into a net secretion. All inhibitory effects were reversible within a short time. Intestinal absorption remained inhibitable compared with controls (p = not significant) after chronic administration of olsalazine even for 1 month. Jejunal monosaccharide absorption was not altered by acute olsalazine perfusion. In the ileum, glucose absorption was significantly inhibited, but the inhibitory capacity of acute olsalazine application decreased significantly (p less than 0.05) depending on duration of olsalazine pretreatment (51% (controls) versus 38% (32 days)). These results point to a complex, acute, but fully reversible effect of olsalazine on intestinal passive and chloride-coupled absorptive processes. Since a mucosal adaptation to these diarrheogenic effects does not occur, the resulting increase in fluid load on the diseased colon may be important in the pathogenesis of olsalazine-related diarrhoea.     

Recent advances in the management of distal ulcerative colitis

The most frequent localization of ulcerative colitis (UC) is the distal colon. In treating patients with active distal UC, efficacy and targeting of the drug to the distal colon are key priorities. Oral and rectal 5-aminosalicylic acid (5-ASA) preparations represent the first line therapy of mild-to-moderate distal UC for both induction and maintenance treatment. It has been reported that many UC patients are not adherent to therapy and that non-compliant patients had a 5-fold risk of experiencing a relapse. These findings led to the introduction of once-daily oral regimens of 5-ASA as better therapeutic options in clinical practice due to improved adherence. New formulations of mesalazine, including the multi-matrix delivery system, and mesalazine granules, which allow once-daily administration, have been developed. They have been demonstrated to be efficacious in inducing and maintaining remission in mild-to-moderate distal UC in large clinical trials. However, existing data for distal UC are rather insufficient to make a comparison between new and classical 5-ASA formulations. It seems that the new formulations are at least as effective as classical oral 5-ASA formulations. Other treatment options, in the case that 5-ASA therapy is not effective, include systemic corticosteroids, thiopurines (azathioprine or 6-mercaptopurine), cyclosporine, infliximab and surgery. The combination of a prompt diagnostic work-up, a correct therapeutic approach and an appropriate follow-up schedule is important in the management of patients with distal UC. This approach can shorten the duration of symptoms, induce a prolonged remission, improve patient's quality of life, and optimize the use of health resources.     

Treatment of ulcerative colitis with oral mesalamine: advances in drug formulation, efficacy expectations and dose response, compliance, and chemoprevention

Sulfasalazine, olsalazine, balsalazide, delayed-release mesalamine, controlled-release mesalamine, mesalamine pellets, and Multi-Matrix System mesalamine are effective first-line therapies for the treatment of mildly to moderately active ulcerative colitis and for subsequent maintenance of remission. For induction therapy it is unclear if there is a dose response above 1.5 g, and for maintenance therapy existing data do not support a dose response above 1.5 g. Sulfasalazine has more frequent side effects than olsalazine, balsalazide, and mesalamine formulations. Once-daily dosing with multi-matrix system mesalamine 1.2 g tablets may lead to optimal compliance. Mesalamine >/= 1.2 g and sulfasalazine >/= 2 g reduce the risk of colorectal cancer in patients with ulcerative colitis. Drug formulations, efficacy expectations and dose response, toxicity expectations, compliance considerations, and chemoprevention considerations are reviewed.     

Mesalazine preparations for the treatment of ulcerative colitis: Are all created equal?

Oral mesalazine(also known as mesalamine) is a 5-aminosalicylic acid compound used in the treatment of mild to moderate ulcerative colitis, with high rates of efficacy in induction and maintenance of remission.The therapeutic effect of mesalazine occurs topically at the site of diseased colonic mucosa. A myriad of oral mesalazine preparations have been formulated with various drug delivery methods to minimize systemic absorption and maximise drug availability at the inflamed colonic epithelium. It remains unclear whether different oral mesalazine formulations are bioequivalent. This review aims to evaluate the differences between mesalazine formulations based on the currently available literature and explore factors which may influence the selection of one agent above another.     

Mesalamine with MMX™ technology for the treatment of ulcerative colitis

Mesalamine with MMX Multi Matrix System^® technology (hereafter referred to as MMX mesalamine) is an oral, high-strength (1.2 g/tablet), once-daily formulation of 5-aminosalicylic acid used for the treatment of ulcerative colitis. This new formulation has been designed to provide delayed and prolonged 5-aminosalicylic acid release throughout the colon. In recent clinical studies, MMX mesalamine (taken as a once-daily dose of 2.4 or 4.8 g) effectively induced clinical remission and mucosal healing versus placebo in patients with active, mild-to-moderate ulcerative colitis. Once remission was achieved, MMX mesalamine effectively maintained disease remission in the majority of patients for at least 12 months. In this paper, we comprehensively review the results of studies exploring the clinical pharmacology, efficacy and safety of MMX mesalamine in patients with ulcerative colitis, and examine the implications of these findings on clinical practice.     

Randomised controlled trial of azathioprine and 5-aminosalicylic acid for treatment of steroid dependent ulcerative colitis

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.     

5-Aminosalicylic acid enema in the treatment of distal ulcerative colitis, proctosigmoiditis, and proctitis

The efficacy and safety of 4-g 5-aminosalicylic acid enemas were assessed in 153 patients with ulcerative colitis involving up to 50 cm of distal colon. Seventy-six patients received active medication and 77 received a placebo. There were 20 dropouts (6 in the active group and 14 in the placebo group) during the study because of insufficient efficacy. After 6 wk of therapy, 48 of the 76 patients (63%) receiving 5-aminosalicylic acid were considered to be "much improved" by the study physician compared to 22 of the 77 patients (29%) on placebo (p = 0.001). A disease activity index based on patient symptoms and sigmoidoscopic appearance was used to assess efficacy. Mean disease activity index declined 55% for patients on 5-aminosalicylic acid and 24% for patients on placebo (p = 0.0001). Analysis of subgroups indicated that patients most likely to respond were those with disease confined to the 20-40 cm from the anus. Response was not affected by concurrent sulfasalazine, but patients requiring concurrent oral steroids had a diminished response. Rapid onset of efficacy was shown by a significant reduction in rectal bleeding within 3 days of treatment initiation. 5-Aminosalicylic acid enemas are well tolerated and are of benefit in the treatment of ulcerative colitis confined to the distal colon.     

The efficacy of oral 5-ASAs in the treatment of active ulcerative colitis: a systematic review

The authors set out to critically review the current data on the efficacy of oral 5-aminosalicylic acid (5-ASA) agents for active ulcerative colitis (UC). Thirty-one studies were identified; 19 met entry criteria. Three trials with mesalamine showed statistical significance versus placebo; those with olsalazine or balsalazide did not. No agent was statistically different from sulfasalazine. In 2 of 3 trials of balsalazide versus mesalamine, results for defined primary and secondary endpoints failed to demonstrate statistically significant differences. Studies suggest that mesalamine is superior to placebo for treating active UC. Five-ASA products appear to be as effective as sulfasalazine, but available data do not suggest a difference in efficacy between any of the 5-ASA preparations.     

Sulphasalazine and 5-aminosalicylic acid in long-term treatment of ulcerative colitis: report on tolerance and side-effects

BACKGROUND: Use of sulphasalazine in ulcerative colitis patients is hampered by a variety of side-effects, including male infertility. 5-aminosalicylic acid is better tolerated and has been increasingly used to treat patients intolerant/allergic to sulphasalazine but it may also be associated with side-effects. AIM: To evaluate tolerance of long-term treatment with sulphasalazine and 5-aminosalicylic acid in ulcerative colitis. METHODS: Side-effects to sulphasalazine (2-3 g/day) and 5-aminosalicylic acid (1.2-2.4 g/day) were recorded in 685 patients: 410 patients received only sulphasalazine, 130 only 5-aminosalicylic acid, and 145 both drugs. In patients with side-effects to sulphasalazine, a desensitisation protocol (rechallenge) was attempted to improve tolerance, and patients still presenting side-effects after desensitisation were switched to 5-aminosalicylic acid. Male fertility was also assessed in 42 males on sulphasalazine and on 5-aminosalicylic acid. RESULTS: Side-effects were observed in 110/555 patients (20%) on sulphasalazine and in 18/275 patients (6.5%) on 5-aminosalicylic acid during a median period of follow-up of 7 and 5 years, respectively. Desensitisation was achieved in 40% of patients intolerant to sulphasalazine. 5-aminosalicylic acid intake induced side-effects in 2/130 patients (1.5%) who had not taken sulphasalazine before versus 4/91 patients (4%) tolerating sulphasalazine and 12/54 patients (22%) intolerant/allergic to sulphasalazine, the difference in incidence of side-effects in the two latter groups being statistically significant (4.4% vs 20.8%, p=0. 001). Fertility was found to be affected in all patients on sulphasalazine but improved when put onto 5-aminosalicylic acid. CONCLUSIONS: 5-aminosalicylic acid should be considered the drug of choice in the treatment of ulcerative colitis bearing in mind that intolerance or allergy may occur in a few patients also on this drug.     

Colon-specific prodrugs of 4-aminosalicylic acid for inflammatory bowel disease

Despite the advent of biological products,such as antitumor necrosis factor-αmonoclonal antibodies(infliximab and adalimumab),for treatment of moderate to severe cases of inflammatory bowel disease(IBD),most patients depend upon aminosalicylates as the conventional treatment option.In recent years,the increased knowledge of complex pathophysiological processes underlying IBD has resulted in development of a number of newer pharmaceutical agents like low-molecular-weight heparin,omega-3 fatty acids,probiotics and innovative formulations such as high-dose,oncedaily multi-matrix mesalamine,which are designed to minimize the inflammatory process through inhibition of different targets.Optimization of delivery of existing drugs to the colon using the prodrug approach is another attractive alternative that has been utilized and commercialized for 5-aminosalicylic acid(ASA)in the form of sulfasalazine,balsalazide,olsalazine and ipsalazine,but rarely for its positional isomer 4-ASA-a wellestablished antitubercular drug that is twice as potent as 5-ASA against IBD,and more specifically,ulcerativecolitis.The present review focuses on the complete profile of 4-ASA and its advantages over 5-ASA and colon-targeting prodrugs reported so far for the management of IBD.The review also emphasizes the need for reappraisal of this promising but unexplored entity as a potential treatment option for IBD.