A double-blind clinical trial to compare the effects of 4-aminosalicylic acid to 5-aminosalicylic acid in topical treatment of ulcerative colitis

The aminosalicylate - folate connection

Two aminosalicylate isomers have been found to possess useful pharmacological behavior: p-aminosalicylate (PAS, 4AS) is an anti-tubercular agent that targets M. tuberculosis, and 5-aminosalicylate (5AS, mesalamine, mesalazine) is used in the treatment of ulcerative colitis (UC) and other inflammatory bowel diseases (IBD). PAS, a structural analog of pABA, is biosynthetically incorporated by bacterial dihydropteroate synthase (DHPS), ultimately yielding a dihydrofolate (DHF) analog containing an additional hydroxyl group in the pABA ring: 2'-hydroxy-7,8-dihydrofolate. It has been reported to perturb folate metabolism in M. tuberculosis, and to selectively target M. tuberculosis dihydrofolate reductase (mtDHFR). Studies of PAS metabolism are reviewed, and possible mechanisms for its mtDHFR inhibition are considered. Although 5AS is a more distant structural relative of pABA, multiple lines of evidence suggest a related role as a pABA antagonist that inhibits bacterial folate biosynthesis. Structural data support the likelihood that 5AS is recognized by the DHPS pABA binding site, and its effects probably range from blocking pABA binding to formation of a dead-end dihydropterin-5AS adduct. These studies suggest that mesalamine acts as a gut bacteria-directed antifolate, that selectively targets faster growing, more folate-dependent species.

Probing the Association of Pancreatitis in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) has been increasingly diagnosed in children and adults. Similarly, acute and chronic pancreatitis are increasingly prevalent conditions with potentially devastating consequences. There is a growing body of literature linking these 2 conditions. The purpose of this review is to provide a comprehensive outline of the association between IBD and pancreatitis and to explore their putative pathophysiology. Based on the collective reports, 2 outstanding reasons for pancreatitis in patients with IBD are medications and IBD complications.

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

Despite the advent of biological products, such as anti-tumor necrosis factor-α monoclonal 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, once-daily 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 well-established antitubercular drug that is twice as potent as 5-ASA against IBD, and more specifically, ulcerative colitis. 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.

Aminosalicylates

Aminosalicylates are the most common drugs for the primary treatment of inflammatory bowel disease. Various pro-drugs and formulations were developed in order to improve pharmacological profiles, optimize bioavailability and to gain highest efficacy in the treatment of ulcerative colitis (UC) and Crohn's disease. In vitro studies have greatly contributed to the understanding of the molecular actions in vivo and clinical studies have proven aminosalicylates to be effective and safe. This review summarizes the current knowledge on the molecular, pharmacological and clinical properties of aminosalicylates with respect to chemoprevention for UC-associated colorectal cancer.

Rectal 5-aminosalicylic acid for induction of remission in ulcerative colitis

BACKGROUND

5-Aminosalicylates (5-ASA) are considered a first-line therapy for inducing and maintaining remission of mild to moderately active ulcerative colitis (UC). When inflammation in UC is limited to the distal colon, 5-ASA can also be administered rectally as a suppository, enema or foam.

OBJECTIVES

A systematic review was undertaken to evaluate the efficacy of rectal 5-ASA for treating active distal UC.

SEARCH STRATEGY

Electronic searches of the MEDLINE database (1966-2008), the Cochrane Central Register of Controlled Trials and the Cochrane IBD/FBD Group Specialized Trials Register were supplemented by manual reviews of reference listings and conference proceedings.

SELECTION CRITERIA

Randomized trials comparing rectal 5-ASA to placebo or another active therapy were eligible for inclusion. Eligible trials enrolled patients with a distal disease margin less than 60 cm from the anal verge or distal to the splenic flexure. Trials that enrolled subjects less than 12 years of age were excluded.

DATA COLLECTION AND ANALYSIS

Eligibility was assessed by three authors. Data were extracted by two authors using standardized forms. Pooled odds ratios (POR) for inducing improvement and remission by symptomatic, endoscopic and histologic criteria were calculated using an intention to treat principle. Fixed effects models were used unless heterogeneity was encountered within groups (P < 0.10), where random effects models were used. All statistical analyses were performed using RevMan 5. Where sufficient data were available, subgroup analyses were performed for disease extent, total daily 5-ASA dose, 5-ASA formulation (enema,suppository, foam) and the type of control intervention (placebo or another active therapy).

MAIN RESULTS

Thirty-eight studies fulfilled the inclusion criteria. Rectal 5-ASA was superior to placebo for inducing symptomatic, endoscopic and histological improvement and remission, with POR for symptomatic improvement 8.87 (8 trials, 95% CI: 5.30 to 14.83; P < 0.00001), endoscopic improvement 11.18 (5 trials, 95% CI 5.99 to 20.88; P < 0.00001), histologic improvement 7.69 (6 trials, 95% CI 3.26 to 18.12; P < 0.00001), symptomatic remission 8.30 (8 trials, 95% CI 4.28 to 16.12; P < 0.00001), endoscopic remission 5.31 (7 trials, 95% CI 3.15 to 8.92; P < 0.00001), and histologic remission 6.28 (5 trials, 95% CI 2.74 to 14.40; P < 0.0001). Rectal 5-ASA was superior to rectal corticosteroids for inducing symptomatic improvement and remission with POR 1.56 (6 trials, 95% CI 1.15 to 2.11; P = 0.004) and 1.65 (6 trials, 95% CI 1.11 to 2.45; P = 0.01), respectively. Rectal 5-ASA was not superior to oral 5-ASA for symptomatic improvement (POR 2.25; 95% CI 0.53 to 19.54; P = 0.27). Neither total daily dose nor 5-ASA formulation affected treatment response.

AUTHORS' CONCLUSIONS

Rectal 5-ASA should be considered a first-line therapy for patients with mild to moderately active distal UC. The optimal total daily dose and dose frequency of 5-ASA remain to be determined. Future research should define differences in efficacy among patient subgroups defined by proximal disease margin and disease activity. There is a strong need for consensus standardization of outcome measurements for clinical trials in ulcerative colitis.

Tolerance of 4-aminosalicylic acid enemas in patients with inflammatory bowel disease and 5-aminosalicylic-induced acute pancreatitis

Derivatives of 5-aminosalicylic acid (5-ASA) used for the treatment of inflammatory bowel disease may induce acute pancreatitis of immunoallergic origin. 4-aminosalicylic acid (4-ASA) differs from its 5-ASA counterpart by the position of the NH2 group and has shown efficacy in ulcerative colitis. The risk of cross intolerance reaction between 5-ASA and 4-ASA has currently never been evaluated. We report three cases of 5-ASA-induced pancreatitis, with no recurrence of pancreatitis during subsequent treatment with 4-ASA enemas. We conclude that 4-ASA enemas are a safe and well-tolerated therapeutic alternative whenever 5-ASA-induced pancreatitis occurs.

Colonic delivery of 4-aminosalicylic acid using amylose-ethylcellulose-coated hydroxypropylmethylcellulose capsules

BACKGROUND

4-Aminosalicylic acid has the potential for use in the treatment of diseases of the colon.

AIM

To assess the feasibility of delivering 4-aminosalicylic acid directly to the colon using a hydroxypropylmethylcellulose capsule coated with a mixture of amylose, a polysaccharide metabolized by bacterial enzymes in the colon, and ethylcellulose.

METHODS

Seven healthy male volunteers received, on three separate occasions, an uncoated or amylose-ethylcellulose-coated hydroxypropylmethylcellulose capsule containing 4-aminosalicylic acid Na (550 mg), or an intravenous injection of 4-aminosalicylic acid Na (135 mg). The capsules were radiolabelled with 99mTc to allow their positions in the gastrointestinal tract to be followed using a gamma camera. Plasma and urine samples were collected and assayed for 4-aminosalicylic acid and metabolite concentrations.

RESULTS

The uncoated capsules broke down within 10 min in the stomach, allowing rapid and complete absorption of the drug. The coated capsules remained intact in the upper gastrointestinal tract, and had a median gastric emptying time of 61 min (interquartile range, 77 min) and a median colon arrival time of 363 min (interquartile range, 185 min). For the coated capsules, only the metabolite was detected in the plasma and/or urine after the capsules had reached the colon.

CONCLUSIONS

The specific coating protected the drug until the capsule reached the colon, where 4-aminosalicylic acid was slowly released and absorbed. Thus, such a formulation has the potential for use in the treatment of inflammatory bowel disease.

Putting rectal 5-aminosalicylic acid in its place: the role in distal ulcerative colitis

Oral aminosalicylates such as sulfasalazine and mesalamine are widely prescribed for the treatment of mild or moderately active distal ulcerative colitis. However, a critical review of the literature demonstrates that rectal 5-aminosalicylic acid (5-ASA) is the optimal therapy for this disease. Meta-analyses of published trials show that rectally delivered 5-ASA is superior to placebo and to conventional rectal corticosteroids in inducing remission of distal ulcerative colitis, whereas the combination of rectal 5-ASA with a rectal corticosteroid or oral aminosalicylate is superior to rectal 5-ASA alone. For maintaining remission of distal ulcerative colitis, rectal 5-ASA is significantly better than placebo and at least as effective as oral 5-ASA. The dosage forms available for rectal delivery include suppositories, foams, and liquid enemas, and selection among these preparations should be guided by the proximal extent of disease and patient preference. The efficacy of rectal 5-ASA is complemented by its low rate of reported adverse effects, which may reflect its reduced potential for systemic absorption. This review summarizes the evidence supporting the role of rectal 5-ASA as a first-line therapy for mild or moderately active distal ulcerative colitis, and offers guidelines for its use.

A meta-analysis and overview of the literature on treatment options for left-sided ulcerative colitis and ulcerative proctitis

OBJECTIVES

Therapeutic trials in left-sided ulcerative colitis (L-UC) and ulcerative proctitis (UP) have lacked control for medication type, dose, delivery, and duration of therapy.

METHODS

All published therapeutic articles and abstracts in L-UC or UP from 1958-1997 were reviewed. Improvement, remission rates, and adverse events were recorded for all (ALL), placebo-controlled (PC) studies, and for PC studies passing quality assessment (QA) scoring. Meta-analysis was used where appropriate.

RESULTS

Left-sided UC: For active disease, 67 studies (17 PC; 10 QA) were identified. Mesalamine enemas achieved remission in a duration but not a dose response (QA), with higher remission rates than steroid enemas (ALL) and clinical improvement rates superior to oral therapies (QA, ALL). Remission maintenance: 17 (six PC, six QA) studies were identified. Mesalamine therapies had comparable remission rates at 6 months, with a possible dose but not delivery effect. Mesalamine enema dosing intervals between QHS to Q3 days maintained efficacy. Reported adverse events were most common with oral sulfasalazine and dose-independent for mesalamine. Withdrawals from therapy were less than placebo, or < or =3%. Ulcerative proctitis: For active disease, 18 (nine PC, three QA) studies were identified. Mesalamine suppositories achieved clinical improvement and remission in a duration but not dose response, with higher rates of remission than topical steroids (ALL). Remission maintenance: three (three PC, two QA) studies were identified. Remission ranged from 75% to 90% (6 months) and 61-90% (12 months) for mesalamine agents. Reported adverse events were most common for mesalamine foam (8%). Withdrawals from therapy were <2%.

CONCLUSIONS

In L-UC and UP, the efficacy and side-effect profile of topical mesalamine are dose independent and superior to oral therapies and topical steroids. Economic analysis suggests that use of these agents will also result in an overall decrease in patient costs.

Antioxidant effects of aminosalicylates and potential new drugs for inflammatory bowel disease: assessment in cell-free systems and inflamed human colorectal biopsies

BACKGROUND

The therapeutic efficacy of 5-aminosalicylic acid in inflammatory bowel disease may be related to its antioxidant properties.

AIM

To compare in vitro the antioxidant effects of conventional drugs (5-aminosalicylic acid, corticosteroids, metronidazole), with new aminosalicylates (4-aminosalicylic acid, balsalazide) and other potential therapies (ascorbate, N-acetylcysteine, glutathione, verapamil).

METHODS

Compounds were assessed for efficacy in reducing the in vitro production of reactive oxygen species by cell-free systems (using xanthine/xanthine oxidase, with or without myeloperoxidase) and by colorectal biopsies from patients with ulcerative colitis using luminol-amplified chemiluminescence.

RESULTS

5-aminosalicylic acid and balsalazide were more potent antioxidants than 4-aminosalicylic acid or N-acetyl-5-aminosalicylic acid in cell-free systems. 5-aminosalicylic acid (20 mM) and balsalazide (20 mM) inhibited rectal biopsy chemiluminescence by 93% and 100%, respectively, compared with only 59% inhibition by 4-aminosalicylic acid (20 mM). Hydrocortisone, metronidazole and verapamil had no significant effect on chemiluminescence in any system. Ascorbate (20 mM) inhibited chemiluminescence by 100% in cell-free systems and by 60% in rectal biopsies. N-acetyl cysteine (10 mM), and both oxidized and reduced glutathione (10 mM), completely inhibited chemiluminescence in cell-free systems, but not with rectal biopsies.

CONCLUSIONS

The antioxidant effects of compounds varies between cell-free systems and inflamed colorectal biopsies. The effect of drugs on the chemiluminescence produced by these two assay systems is useful for screening potentially new antioxidant treatments for inflammatory bowel disease. Ascorbate seems worth further study as a novel therapy.

Innovations in topical therapy

Topical therapy can be considered the standard treatment for distal ulcerative colitis. The group of drugs of first choice are the aminosalicylates which are effective in inducing remission in acute disease as well as in preventing relapse. Corticosteroids appear to be slightly less effective and have no proven benefit in maintenance therapy. With new topical steroids, such as budesonide, systemic effects can be minimized. The major role of corticosteroids is to complement aminosalicylates, when necessary. The new topical compounds appear to be especially valuable when there is a long-term requirement for corticosteroids. With the vast majority of patients obtaining remission with standard treatment, it is difficult to make the case for alternative substances. Short-chain fatty acids, local anaesthetics and bismuth compounds seem to be the most promising innovations in topical therapy although their equivalence or even superiority to mesalazine has not been established.

Controlled trial of 4-ASA in ulcerative colitis

A six-week placebo-controlled trial of the efficacy and safety of 6 g per day of 4-aminosalicylic acid (4-ASA) was conducted in 30 subjects with mild to moderately severe ulcerative colitis. Subjects were stratified into groups having distal (< 60 cm) or more extensive (> 60 cm) disease. Diarrhea, bleeding, sigmoidoscopic and biopsy appearance, and physician global assessment were scored to judge efficacy. Safety was evaluated by monitoring untoward symptoms and laboratory values. Median percent improvement was significantly greater (P < 0.05) in the 4-ASA > 60-cm group (42.7%) than in the placebo > 60-cm group (21.2%), but 4-ASA was not better than placebo for the < 60-cm group or the total study group. Severe dyspepsia (one subject), abnormal AST (transient in five, persistent in one) and elevated lipase without pancreatitis (six subjects) were noted. Thus 6 g 4-ASA for six weeks was more effective than placebo in mild to moderate ulcerative colitis extending more than 60 cm above the anus, but not in distal disease, and the drug was generally well tolerated.

Salicylates for ulcerative colitis--their mode of action

Delivery of 5-aminosalicylic acid to the colon by sulphasalazine, other azo-bonded compounds and controlled-release preparations is introduced in the context of metabolism by epithelial cells and therapeutic efficacy in ulcerative colitis. Potential modes of action are then reviewed, including actions on luminal bacteria, epithelial cell surface receptors, cellular events (such as nitric oxide release or butyrate oxidation), electrolyte transport and epithelial permeability. Evidence for an influence of salicylates on circulating and lamina propria inflammatory cells is presented, as well as actions on adhesion molecules, chemotactic peptides and inflammatory mediators, such as eicosanoids, platelet-activating factor, cytokines or reactive oxygen metabolites. The precise mechanism will remain uncertain as long as the aetiology of ulcerative colitis is unknown, but a pluripotential mode of action of salicylates is an advantage when influencing the network of events that constitute chronic inflammation.

Oral 4-aminosalicylic acid versus 5-aminosalicylic acid slow release tablets. Double blind, controlled pilot study in the maintenance treatment of Crohn's ileocolitis

4-Aminosalicylic acid (4-ASA) has been suggested as an effective treatment for both active and quiescent ulcerative colitis. 5-Aminosalicylic acid (5-ASA) is well accepted for the maintenance treatment of inactive ulcerative colitis. Moreover, recent studies suggest that 5-ASA may also be effective in maintaining remission in Crohn's colitis. As treatment with 4-ASA may result in less side effects, the efficacy of a one year's maintenance treatment with oral 4-ASA (1.5 g/d, slow release tablets, n = 19) and oral 5-ASA (1.5 g/d, slow release tablets, n = 21) was compared in a double blind, randomised trial in patients with quiescent Crohn's ileocolitis. Patients with ileocolonic or colonic involvement were enrolled if in stable remission for more than two months but less than one year. Baseline demography and clinical severity were similar in both groups. Total colonoscopy and ileoscopy were performed at enrollment and at the end of the study. After one year seven of 19 patients receiving 4-ASA (36%) and 8 of 21 receiving 5-ASA (38%) had developed a clinical relapse, as defined by a rise in the Crohn's disease activity index (CDAI) of more than 100 points to values higher than 150. The relapse rates between the 4-ASA and the 5-ASA groups were not statistically different although no comparison with the spontaneous relapse rate in a placebo group could be made. Clinical relapse was accompanied by a statistically significant rise in serum concentrations of soluble interleukin 2 receptor and by an increased percentage of activated peripheral blood T cells. There were no statistical differences between the 4-ASA and the 5-ASA groups regarding the height of rise in CDAI or of soluble interleukin 2 receptor concentrations during relapse, thus showing a similar severity relapsed disease activity. In conclusion, 4-ASA maybe as effective as 5-ASA in the maintenance treatment of quiescent Crohn's disease and there were no differences in the severity of relapse between both treatment groups.

Current management of inflammatory bowel disease

The aetiology of ulcerative colitis and Crohn's disease remains unknown. While this remains so, treatment must be directed towards pathogenetic mechanisms. Corticosteroids, sulphasalazine and the new salicylates, the immunosuppressants azathioprine, 6-MP and, more recently, cyclosporin and metronidazole have become the accepted and standard forms of treatment. The importance of maintaining nutritional status is often overlooked but must be considered in every patient. Recognition of the occurrence of disease in all age groups, and in particular in children and adolescents, is also important, as is an appreciation of the special problems involved. The possibility of surgery at some stage of the disease should be raised with the patient. As the pathogenetic mechanisms of inflammatory bowel disease are further elucidated, new forms of treatment will be developed. This is already happening, with studies looking at such agents as immunoglobulin G, eicosapentaenoic acid and a new specific inhibitor of 5-lipoxygenase. These offer hope of more potent drugs with low side-effect profiles that may complement or replace the currently available agents used in the management of inflammatory bowel disease.

Double blind, controlled trial of 4-aminosalicylic acid and prednisolone enemas in distal ulcerative colitis

Corticosteroid or 5-aminosalicylic acid enemas are the treatment of choice for distal ulcerative colitis but up to one third of patients may be unresponsive. As an alternative therapy might be advantageous, the efficacy of six weeks' treatment with 2 g 4-aminosalicylic acid (4-ASA) (n = 24) and 20 mg prednisolone enemas (n = 21) were compared in a double blind, randomised trial in patients with acute distal (less than 30 cm from the anus) ulcerative colitis. Baseline demography and clinical severity were similar in both groups. Five of 24 patients receiving 4-ASA and 4 of 21 receiving prednisolone did not complete the trial because of deteriorating symptoms, failure to improve, or side effects. At the time of leaving the trial, 24 hour stool frequency, the presence of blood in the stools, and histological and sigmoidoscopic appearances were similar in both groups. Symptomatic improvement occurred in 17 of 24 patients receiving 4-ASA compared with 11 of 21 receiving prednisolone (chi 2 = 1.62, NS). Complete symptomatic improvement occurred in 9 of 24 patients receiving 4-ASA compared with 5 of 21 receiving prednisolone (chi 2 = 0.98, NS). Histological improvement was seen in 9 of 24 patients on 4-ASA compared with 7 of 21 on prednisolone (chi 2 = 0.08, NS). One patient receiving 4-ASA was considered to have an idiosyncratic reaction to the drug but other side effects were not considered to be drug related. Thus, 4-ASA, previously used in the treatment of tuberculosis (para-aminosalicyclic acid), is as good as prednisolone in the treatment of distal ulcerative colitis and should be considered in patients unresponsive to steroids or in whom steroid treatment is undesirable.

A prospective randomized double blind trial comparing prednisolone and 4-aminosalicylic acid enemas in acute distal ulcerative colitis

A prospective double blind and randomized study was conducted to compare 4-aminosalicylic acid (4-ASA) and prednisolone-21-phosphate enemas in inducing remission in patients with acute distal ulcerative colitis. Patients with ulcerative colitis distal to the splenic flexure as assessed by flexible colonoscopy, barium enema and histology were included in the study. Of 40 consecutive patients, 20 were randomized to each of the two treatment groups. Clinical evaluation was done weekly; sigmoidoscopy and histology were performed at entry and at the end of 4 weeks. Therapy was discontinued in four patients treated with prednisolone enemas due to worsening of symptoms. The clinical improvement was significant in the remaining patients (P less than 0.001) and was similar in the two groups (P greater than 0.1). Sigmoidoscopic and histological improvement were better with 4-ASA than with prednisolone enemas. No adverse effects were observed in any of the patients treated. The present study suggests that 4-ASA is a safe and effective treatment for inducing remission in acute distal ulcerative colitis.

Placebo-controlled trial of ulcerative colitis with oral 4-aminosalicylic acid

Forty patients with active ulcerative colitis were randomly assigned to receive either 4 g of oral enterically coated 4-aminosalicylic acid (para-aminosalicylic acid) or placebo. The duration of treatment was 12 weeks. Disease activity was assessed by grading clinical symptoms of blood, mucus, urgency, sigmoidoscopic findings, and degree of histological inflammation in rectal biopsy specimens. At 12 weeks, 11 of 20 patients (55%) who received 4-aminosalicylic acid showed improvement in clinical and sigmoidoscopic variables. In contrast, only 1 of 20 patients (5%) who had received placebo showed improvement (P less than 0.005). Eighteen of the 19 patients in the placebo group who showed no improvement were treated subsequently with open-label 4-aminosalicylic acid. Of the 18, 11 showed clinical and sigmoidoscopic improvement. Patients allergic or intolerant to sulfasalazine with extensive disease were more likely to respond to 4-aminosalicylic acid.

The production of an amine-modified derivative of 5-aminosalicylic acid by activated neutrophils. Roles for myeloperoxidase and chloride ions

Following incubation with activated neutrophils, two metabolites of 5-aminosalicyclic acid (5-ASA) were identified by HPLC. These two metabolites accounted for approximately 60% and 20% of the original 5-ASA. The formation of the major metabolite was prevented by pre-incubation with the peroxidase inhibitor, azide, and reduced by the omission of chloride ions from the incubation medium, or the presence of catalase. A similar product was generated by sodium hypochlorite or myeloperoxidase/H2O2, mass spectroscopical analysis being consistent with it being 5-nitroso-salicylate. Our finding suggests that the efficacy of 5-ASA results from its ability to react with and so scavenge hypochlorite ions. The amount of amine-modified 5-ASA in the faecal stream may thus provide an indicator for hypochlorite production in the bowel.

Mesalamine in ulcerative colitis

Sulfasalazine has been used for many years in the management of ulcerative colitis. As many as 20 percent of patients treated with it experience intolerable adverse effects usually attributed to its sulfapyridine component. The other active component is 5-aminosalicylic acid (5-ASA); the only 5-ASA enema preparation currently available in the U.S. is mesalamine (Rowasa, Reid-Rowell) containing 5-ASA 4 g in 60 mL. In clinical trials, mesalamine has proved efficacious in treating refractory cases of distal ulcerative colitis, proctitis, and proctosigmoiditis. Because of its high cost compared with more conventional treatment modalities, it should be reserved for cases that are either refractory or intolerant to conventional treatment.

Luminal concentrations of orally ingested 4-aminosalicylic acid as determined by in-vivo equilibrium dialysis

We measured 4-aminosalicylic acid (4-ASA) levels in faecal water by in-vivo equilibrium dialysis during oral ingestion of drug by two different dose protocols (A and B). In Protocol A, 5 normal subjects ingested 3 g of 4-ASA as the free acid and 20 mg of metaclopromide per day. On Day 5, small dialysis sacs filled with dextran 40 were ingested and the oral drug was continued until the sacs were retrieved from the stool. Protocol B followed the same format except that 3 g of 4-ASA was ingested twice daily and metaclopromide was omitted. In both protocols concentrations of 4-ASA and N-acetylated 4-ASA in sac contents were measured by HPLC. In-vitro dialysis studies showed bi-directional equilibrium was reached within 120 min. During Protocol A, intraluminal concentrations of total 4-ASA ranged from 14.0 to 32.2 mmol/L with a mean of 20.6 mmol/L. With Protocol B, total 4-ASA levels ranged from 20.1 to 41.3 mmol/L with a mean of 33.9 mmol/L. From 90 to 99% of the drug in the dialysates was N-acetylated. These concentrations of total 4-ASA are similar to those of 5-ASA after ingestion of therapeutic doses of sulphasalazine or absorption-resistant formulations of 5-ASA. Thus, oral 4-ASA could have a role in the treatment of inflammatory bowel disease.

New salicylate therapies for ulcerative colitis

Since the development of sulfasalazine about a half century ago, the prognosis for patients with ulcerative colitis has improved significantly. Very recently, the active moiety of oral sulfasalazine, 5-aminosalicylic acid, has been made available as a topical (enema) preparation. In this article, Dr. Bruckstein reviews the advantages of the enemas in the treatment of ulcerative colitis and briefly examines the potential benefits of the new oral salicylate preparations.

Newer pharmacologic agents for the therapy of inflammatory bowel disease

Topical 5-ASA Agents. Observations that 5-ASA may be the clinically active component of sulfasalazine have stimulated extensive pharmaceutical efforts to develop a new class of agents for the treatment of the inflammatory bowel diseases. Both oral and rectal forms of 5-ASA have been designed, tested, and released for use in Europe and Canada. Only one rectal 5-ASA formulation is now commercially available in the United States. Studies with topical 5-ASA have demonstrated that this formulation is safe and effective for distal colitis, even in patients with disease refractory to standard therapy. Adverse effects of topical 5-ASA are minimal. However, optimal treatment doses have not been defined, relapse is common after withdrawal of therapy, and issues regarding maintenance regimens are not yet resolved. Other disadvantages include the expense and inconvenience of enema therapy. However, rectally administered 5-ASA is an appropriate initial therapy for the treatment of distal ulcerative colitis, or as a therapeutic option for refractory distal colitis. Data are insufficient to make recommendations regarding the use of topical 5-ASA in Crohn's disease. Whether this class of agents will be of benefit for Crohn's proctitis or for perineal disease must await further clinical trials. Oral 5-ASA Agents. There appears to be a well-substantiated benefit equivalent to that of sulfasalazine achieved by the new oral formulations of 5-ASA when used for the treatment of acute mild to moderate ulcerative colitis, and as maintenance treatment of ulcerative colitis in remission. Adverse reactions to these agents are uncommon, usually mild, and infrequently require withdrawal of therapy. The major problem reported with these agents is watery diarrhea, most commonly associated with olsalazine, but the practical importance of this adverse effect is disputed. Rare occurrences of reversible pericarditis and acute pancreatitis have been encountered during clinical application of these agents. As more experience is obtained, these agents may become the initial therapy of choice for the treatment of mild to moderate ulcerative colitis and for maintenance in inactive disease. Currently available data have defined a role for these agents as an important alternative for the treatment of patients intolerant or allergic to sulfasalazine. As with sulfasalazine, these agents should not be used as the sole treatment for severely active ulcerative colitis. Many unanswered questions remain regarding therapy with these agents for ulcerative colitis. Still undefined are optimal drug dosages, appropriate dosing intervals, and the necessary duration of therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Topical treatment of ulcerative colitis

It is clear that the therapeutic options available for the treatment of ulcerative proctosigmoiditis have increased over the last few years and in the future additional therapies will be available. Therapy will have to be individualized. Studies to date have generally failed to confirm the superiority of one form of treatment over another, although there is some evidence that high-dose 5-ASA enemas are superior to hydrocortisone enemas. Patients who fail to respond to one form of therapy may respond to another therapeutic modality. Continued evaluation of topical therapies provides not only an opportunity to improve the treatment prospects for patients but also allows for examination of potential mechanisms of action of therapeutically active compounds. Future research directions should also include assessment of combination therapy, the more widespread use of suppositories, and strategies to encourage patient compliance. Larger multicenter trials are needed to assess the effectiveness of some of the newer compounds. The role of topical therapy for patients with Crohn's disease confined to the left colon requires evaluation.

Mesalazine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in chronic inflammatory bowel disease

Mesalazine (5-aminosalicylic acid; mesalamine), the active moiety of sulphasalazine (salazosulfapyridine), is available in specially formulated oral and rectal forms for the treatment of active ulcerative colitis of mild to moderate severity and for maintenance therapy during disease remission. Tablets or capsules coated with acrylic-based resin and tablets containing microgranules coated with ethylcellulose deliver mesalazine to the distal small intestine and colon, thus avoiding the need for the carrier, sulphapyridine, which is responsible for many of the adverse effects associated with sulphasalazine. Since mesalazine is released in the small intestine from some coated preparations in contrast to sulphasalazine, these oral formulations have therapeutic potential in Crohn's disease. A limited number of therapeutic trials suggest that orally administered mesalazine 1.5 to 2.4g daily is of similar efficacy to sulphasalazine 2 to 3g daily in patients with mild to moderate ulcerative colitis. The efficacy of mesalazine enemas has been more widely investigated, a dose of 1 to 4g once daily being consistently more effective than placebo and apparently similar to enemas of prednisone 25mg or oral sulphasalazine 3g. Initial results suggest that mesalazine 4g enemas may be more effective than those containing hydrocortisone 100mg. Mesalazine and sulphasalazine in approximately equivalent oral dosages are similarly effective in maintaining remission in ulcerative colitis. Orally administered coated mesalazine is generally well tolerated by about 85% of patients allergic to or intolerant of sulphasalazine, the remainder experiencing similar reactions to both drugs. Adverse effects of mesalazine enemas are confined to local irritation and effects resulting from enema-tip insertion. Thus, orally administered coated mesalazine is a suitable alternative to sulphasalazine in the treatment of patients with mild to moderate active distal ulcerative colitis and for maintaining remission particularly in patients allergic to or intolerant of sulphasalazine. In patients who find enema therapy acceptable, mesalazine enemas are effective and well tolerated.

Immunosuppressive drugs in inflammatory bowel disease. A review of their mechanisms of efficacy and place in therapy

Immune effector mechanisms are central to the disease process in inflammatory bowel disease, but it is not clear whether the mucosal or systemic immunological abnormalities are primary phenomena, or are secondary to disease activity. Corticosteroid drugs remain the most effective treatment for active disease, but there is no evidence that they are useful for maintenance therapy. Some patients, however, are dependent on low-dose corticosteroids, and relapse when the drug is withdrawn. These drugs have widespread actions on the immune response, and monocytes are particularly sensitive to corticosteroids. In contrast, sulphasalazine and 5-aminosalicylic acid are effective in maintenance therapy, but do not act primarily by immunosuppressive mechanisms. They are effective in maintenance therapy of ulcerative colitis, and mild relapses of ulcerative colitis and colonic Crohn's disease. New preparations of 5-aminosalicylic acid have reduced side effects, many of which are due to sulphapyridine. Azathioprine and 6-mercaptopurine are used less widely: in Crohn's disease there is reasonable evidence for benefit in chronic active disease unresponsive to corticosteroids, and maintenance of remission. In ulcerative colitis, the position is less clearcut. Overall, trials favour an effect in chronic active disease, and there are pointers to an effect in maintenance of remission. Because of their side effects, in particular marrow suppression, these drugs should be reserved for second-line therapy. Similarly, other cytotoxic drugs are not used because of their side effects. More recently, cyclosporin A, with its selective action on interleukin-2 release and/or synthesis, and inhibition of helper T cell function, has been shown to be helpful in Crohn's disease. At present it should only be used in controlled trials, for patients with unresponsive disease in whom surgery is contraindicated. Renal toxicity may limit long term use. There is little data for cyclosporin A in ulcerative colitis. On the basis that there may be an underlying immune defect in Crohn's disease leading to mucosal inflammation, immunostimulant therapy has been used, but there is no evidence for benefit from treatment with BCG or levamisole in active disease or in maintenance therapy. 7S-Immunoglobulin, plasmapheresis or T-lymphocyte apheresis have been used in acute relapse, but evidence is anecdotal, and does not support their use except as a desperate measure to avoid surgery. Further well-designed controlled trials are needed to define the role of all these drugs, and further research into the mechanism of action on the immune response may shed light on the pathogenesis of inflammatory bowel disease.

Experience with topical administration of 4-aminosalicylic acid in ulcerative colitis

4-Aminosalicylic acid was applied topically in a daily dose of 1.4 gm for two weeks in ten patients with ulcerative colitis. After favorable results, the therapeutic effects of 4-aminosalicylic acid and salazopyrin enemas were compared in a two-week cross-over open trial, in 20 patients suffering from recurrent ulcerative colitis involving the rectum and rectosigmoid. No significant difference was found in the changes of the endoscopic picture of the mucosa. The results did not show a significant difference between 4-aminosalicylic acid and salazopyrin enemas, either in the clinical activity or in the histologic picture. 4-Aminosalicylic acid seems to be a suitable drug for improving the clinical symptoms of ulcerative proctitis.

Newer 5-aminosalicylic acid based drugs in chronic inflammatory bowel disease

Since the discovery that 5-aminosalicylic acid (5-ASA) is the active moiety of sulphasalazine in the treatment of chronic inflammatory bowel disease, several new 5-ASA based drugs have been developed. These consist either of slow- or delayed-release formulations of plain 5-ASA or sulpha-free azo compounds of 5-ASA. The different formulations and compounds have varying bioavailabilities, which makes it possible to use them alternatively in different clinical situations. A review of the literature is given, together with suggestions as to how the new drugs might be used in different clinical situations.

Double-blind comparison of slow-release 5-aminosalicylate and sulfasalazine in remission maintenance in ulcerative colitis

The results of a clinical trial comparing slow-release 5-aminosalicylic acid tablets (Pentasa) and enteric-coated sulfasalazine tablets (Salazopyrin) with regard to the efficacy of maintaining ulcerative colitis patients in remission for 12 mo and with regard to safety of treatment are reported. Seventy-five patients with ulcerative colitis in remission for between 1 mo and 5 yr were included for analysis. Forty-nine men and 26 women, aged between 18 and 79 yr, received either Pentasa t.i.d. (1500 mg) plus Salazopyrin placebo or Salazopyrin t.i.d. (3 g) plus Pentasa placebo daily. Patients were assessed clinically, endoscopically, and histologically before and 3, 6, 9, and 12 mo after the start of treatment. Life-table analysis showed ongoing remission after 6 and 12 mo for Pentasa to be 63% (26 of 41) and 54% (22 of 41) and for Salazopyrin 72% (22 of 31) and 46% (14 of 31). These differences were not statistically significant. Three patients treated with Salazopyrin were withdrawn because of severe erythrodermia, anxiety and backache, and pregnancy, respectively. One patient on Salazopyrin experienced transient rises in serum urea, creatinine, and lactic dehydrogenase and another patient in this group reported slight reversible loss of hair. In the Pentasa group no side effects were recorded. We conclude that Pentasa is a well-tolerated drug, equally effective as Salazopyrin in maintenance of remission of ulcerative colitis.

Medical treatment of ulcerative colitis: scoring the advances

Recently, oenological prejudices were challenged by the use of a points scoring system (from 50 to 100) to evaluate wine in a book now widely regarded as one of the most authoritative. On this scale, a 1981 Chateau Citran described as 'emaciated' scored 65, a 1983 Chateau Kirwan scored 85, and a 1982 Petrus 100. If the same approach were used for drugs used in ulcerative colitis to quantify an advance over conditions existing at the time of its introduction how would they score? Because they were the first available drugs in their class and clearly constituted major advances, corticosteroids and sulphasalazine both score 95, the score being limited by a high level of side effects. The new salicylates score 75, because they extend the benefits of sulphasalazine to a minority of patients but they have the potential to score 90 if increased dosing and greater effectiveness over sulphasalazine can be achieved. Salicylate enemas score 80, because they advance treatment over topical corticosteroids for patients with resistant distal disease, but the mode of delivery needs improvement. Steroid foams also score 80, particularly if the patient's vote is taken into account. Azathioprine's score cannot be calculated because there is doubt over its efficacy, but it is potentially 88 if it saves patients with difficult disease from colectomy. We can only guess what an oral non-absorbed steroid would score, but if response rates for relapse were substantially improved, or if corticosteroids could be used as effective maintenance treatment, it could be as high as 95. There are indications that we should 'watch this space'.

Review: new aminosalicylic acid derivatives for the treatment of inflammatory bowel disease

Up to 20-30% of patients treated with sulphasalazine experience a variety of adverse effects, principally due to the carrier moiety sulphapyridine. In the last decade there has been a major drive to develop a new generation of 5-aminosalicylic acid (5-ASA) and 5-ASA-related drugs which not only have a high efficacy but are also devoid of the unwanted side-effects of sulphapyridine. Various forms of 5-ASA have been evaluated in ulcerative colitis and appear to be effective orally in preventing relapse and topically in the treatment of active distal colitis. More recently, topical 4-ASA has been found to be useful for the treatment of distal colitis with the advantage of better stability and lower cost compared with 5-ASA. In the foreseeable future it seems likely that these new aminosalicylic acid derivatives will become the drugs of choice in the treatment of inflammatory bowel disease and largely replace sulphasalazine.

4-Aminosalicylic acid, in contrast to 5-aminosalicylic acid, has no effect on arachidonic acid metabolism in human neutrophils, or on the free radical 1,1-diphenyl-2-picrylhydrazyl

5-Aminosalicylic acid seems to be the active moiety of sulfasalazine in the treatment of chronic inflammatory bowel disease. Even if the precise mode of action is obscure, it is assumed that two of the main mechanisms are inhibitory effects on the lipoxygenation of arachidonic acid and interaction with free radicals. As 4-aminosalicylic acid has been claimed to be beneficial in the topical treatment of ulcerative colitis, it was tested whether this drug possesses any influence on the 5-lipoxygenase activity in human neutrophils in vitro or whether it acts as a radical scavenger. The change of the amino residue from carbon-5 to carbon-4 abolished the effect in the two systems tested. The reported clinical observations on 4-aminosalicylic acid in the treatment of chronic inflammatory bowel disease remain to be confirmed and cannot be explained by interference with arachidonic acid metabolism or free oxygen radicals.

5-Aminosalicylic acid enemas: effective agent in maintaining remission in left-sided ulcerative colitis

The efficacy of 5-aminosalicylic acid enemas in maintaining remission in left-sided ulcerative colitis was studied. Twenty-five patients in remission for at least 2 mo were randomized to receive either 1-g 5-aminosalicylic acid or placebo enemas daily and were followed up for 1 yr. Eleven of 13 patients randomized to placebo relapsed after a mean of 16 wk. Nine of 12 patients randomized to 5-aminosalicylic acid remained in remission for 1 yr, 2 others in remission withdrew by request, and 1 relapsed at 10 wk. The difference between relapse rate on 1-g 5-aminosalicylic acid versus placebo was significant (p less than 0.005). Seven patients entered the blinded trial a second time. Three of 4 patients randomized to 5-aminosalicylic acid remained in remission and 1 relapsed. Three randomized to placebo relapsed at a mean of 14 wk. One-gram 5-aminosalicylic acid enemas are safe and effective in maintaining remission in patients with left-sided ulcerative colitis.

Efficacy of 5-aminosalicylic acid enemas versus hydrocortisone enemas in ulcerative colitis

A controlled trial has been carried out in order to compare the efficacy of enemas containing a high dosage of 5-ASA (4 g) versus enemas containing hydrocortisone 100 mg. The trial was conducted on 86 patients, 44 of whom received 5-ASA and 42 received hydrocortisone. The results were favorable in terms of clinical, sigmoidoscopic, and histologic criteria for 5-ASA treatment. Other aspects have been investigated, such as retrograde spread of enemas which have been shown to reach the left colon. No nephrotoxicity was detected. The long term experience confirmed the preliminary positive results.

Proctocolitis unresponsive to conventional therapy. Response to 5-aminosalicylic acid enemas

We report results of a prospective study of daily 5-ASA enema therapy in patients with proctocolitis that was unresponsive to conventional therapy. Forty-seven patients with active colonic inflammation distal to the splenic flexure have been followed for three months to three years. Rapid improvement was noted within three months in 41 of 47 (87%) patients, while six failed therapy. Of the 41 patients responding to therapy, 39 achieved complete remission. Nineteen patients have relapsed at least once following discontinuation of 5-ASA, but 23 of 25 (92%) relapse episodes responded to a course of 5-ASA therapy. Complications of 5-ASA therapy were limited to hemorrhoidal irritation and local perianal injury. We conclude that 5-ASA enema is effective in inducing remission in patients with proctocolitis unresponsive to conventional therapy.

4-Aminosalicylic acid retention enemas in treatment of distal colitis

Forty-five of 47 patients with distal ulcerative colitis completed a two-week double-blind, randomized, controlled trial to determine if 4-aminosalicylic acid (4-ASA) enemas, 1 g bid or 2 g bid, were therapeutically effective compared to placebo. Forty-one patients enrolled because they were refractory to or had side effects during conventional therapy with sulfasalazine or corticosteroids. Proctoscopic examination was done before and after two weeks of treatment. Patients kept daily diaries assessing: blood in stools, mucus in stools, tenesmus, abdominal pain, loss of appetite, fatigue, weight loss, and malaise. Severity of each symptom ranged from 0 (absent) to 3 (severe). A total severity score was calculated from the above for each patient. At the end of the two-week study, 35 patients elected to take 4-ASA in an open-label trial for one year. 4-ASA enemas in the 1-g bid but not the 2-g bid dosage were significantly more effective in improving symptoms than placebo: P less than or equal to 0.05. Neither dose of 4-ASA enema was better than placebo in improving the sigmoidoscopic appearance at the end of two-weeks. Forty-six percent of patients had complete resolution of all signs and symptoms in the open-label trial and 31% were better but still had sigmoidoscopic evidence of disease, a total response rate of 77%. Side effects were similar in the placebo and 4-ASA groups. We conclude that 4-ASA enemas in a dose of 1 g bid are safe and effective in the treatment of distal ulcerative colitis.

Effect of 5-aminosalicylic acid (5-ASA) and other salicylates on short-chain fat metabolism in the colonic mucosa. Pharmacological implications for ulcerative colitis

5-Aminosalicylic acid (5-ASA) suppressed nitrite-stimulated oxidation of the fatty acid n-butyrate in a dose-dependent manner in isolated human and rat colonic epithelial cells. 4-ASA had one-sixth of the capacity of 5-ASA and sulphapyridine (SP) little of the capacity of 5-ASA to suppress fatty acid oxidation in human colonic epithelial cells. Sulphasalazine (SASP), azodisalicylic acid (ADS), acetyl-5-ASA and acetyl salicylic acid (ASA) did not suppress fatty acid oxidation in rat colonocytes. The suppression index of fatty acid oxidation (SIFO) of respective salicylic acids correlated with the reported clinical effectiveness of each drug against ulcerative colitis (UC). The capacity of 5-ASA to affect nitrite-stimulated oxidation of fat in the colonic mucosa suggests that nitrite ions and control of fatty acid oxidation play a central role in the development and therapy of active UC.