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

Oroileal transit of slow release 5-aminosalicylic acid

The predominant active anti-inflammatory moiety in chronic inflammatory bowel disease is 5-aminosalicylic acid (5-ASA). As unprotected 5-ASA is rapidly absorbed in the upper gastrointestinal tract several slow release preparations have been developed to permit passage of 5-ASA to the lower small bowel and to the colon. To investigate luminal kinetics and extent of the release of 5-ASA intraluminal concentrations and loads of this compound together with that of its main metabolite acetyl-5-aminosalicylic acid (ac-5-ASA) were studied, over 15 hours after giving the slow release preparation Salofalk at a dose of 500 mg orally together with a test meal. Plasma concentrations and urinary excretion were also measured. Six healthy volunteers swallowed an 11 lumen oroileal tube, which allowed marker perfusion, aspiration of luminal content from the duodenum, mid-jejunum, and ileum, and recording of intestinal motility. Emptying of 5-ASA into the duodenum started after emptying of the meal, together with the first phase III of interdigestive motility. Mean luminal concentrations of 5-ASA and ac-5-ASA increased continuously from duodenum (both: 15 to 30 micrograms/ml) to ileum (60 to 110 micrograms/ml and 80 to 150 micrograms/ml respectively) over three hours and decreased over the next three hours. During 10 hours after eating, 30% of the total dose passed the ileum in solution and another 10% were excreted in urine. Thus about 60% reached the colon unreleased from tablets and another 30% were in solution. The ratio of 5-ASA and ac-5-ASA in solution was about 1:1 in the duodenum and 1:1.5 to 1:2 in the more distal small intestine. The data suggest that the large quantities of intraluminal ac-5-ASA are generated in the intestinal mucosa and reach the lumen by back diffusion. The results show that most of the 5-ASA from this slow release preparation is delivered into the colon, which explains its effectiveness in ulcerative colitis. The considerable luminal concentrations already present in the distal ileum might justify therapeutic trials in Crohn's disease.

Lung disease associated with orally administered mesalamine for ulcerative colitis

Pulmonary symptoms, bilateral interstitial infiltrates and gas exchange abnormalities developed in a patient with ulcerative colitis treated with orally administered mesalamine. Improvement of symptoms and objective findings occurred after drug discontinuation. To the best of our knowledge, this is the first report of lung toxicity associated with orally administered mesalamine.

8-Hydroxydeoxyguanosine in vitro: effects of glutathione, ascorbate, and 5-aminosalicylic acid

Oxidative DNA damage, as expressed by 8-hydroxydeoxyguanosine (8-OHdG), was investigated in calf thymus DNA exposed to either ultraviolet radiation or to FeCl2/H2O2 in a Fenton-like reaction. The influence of iron (absent in the UV system and present in the FeCl2/H2O2 system) and pH (7.4 and 4.0) on the effect of glutathione (GSH), ascorbate, and 5-aminosalicylic acid (5-ASA, a drug used in the treatment of chronic inflammatory bowel diseases) was examined in these systems. Without iron, all three compounds considerably reduced 8-OHdG formation (i.e., acted as scavengers), while in the presence of iron salts, 8-OHdG formation was accelerated (except for GSH at pH 7.4), i.e., the compounds acted as prooxidants. This effect was augmented at low pH. The prooxidant property of 5-ASA may have implications for its clinical use. Maximum scavenging effect for all the compounds investigated was obtained at much lower doses than the maximum enhancing effect. This demonstrates that to the end of oxy-radical scavenging, the concentration of the GSH, ascorbate, and 5-ASA, respectively, should be chosen to obtain maximum antioxidant effect and minimum prooxidant effects. The significance of this finding for the selection of antioxidant dose is important but remains to be investigated further.

Involvement of oxygen-derived free radicals in the pathogenesis of chronic inflammatory bowel disease

Ulcerative colitis and Crohn's disease are chronic inflammatory bowel diseases. The most widely prescribed drug for treatment of these diseases, sulfasalazine, has been shown to inhibit the activity of free radicals, as the active moiety of sulfasalazine, 5-aminosalicylic acid, is a radical scavenger. This effect of 5-aminosalicylic acid may be of clinical relevance, as a recent study has shown that 5-aminosalicylic acid reacts with oxygen-derived free radicals formed in the intestine in this disease. Reaction with free radicals does not, however, occur in patients with rheumatoid arthritis treated with the same agent. Furthermore, a significant correlation exists between the activity in the intestine of free radicals, as measured by the rate of lipid peroxidation, and the disease activity.

Pharmacokinetics of rectal drug administration, Part II. Clinical applications of peripherally acting drugs, and conclusions

Part I of this article, which appeared in the previous issue of the Journal, covered general considerations, the physiology of the rectum, spreading of drugs into the colon, rectal absorption, partial avoidance of first-pass elimination, rate-controlled rectal delivery of drugs, irritation of the rectal mucosa and clinical applications of rectal administration, and discussed centrally acting drugs. In Part II, this discussion is extended to drugs which act peripherally and to methods of enhancing rectal drug absorption. The overall summary appeared in Part I.

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

Olsalazine (sodium azodisalicylate; azodisal sodium) is an anti-inflammatory agent designed to deliver its active moiety, mesalazine (5-aminosalicylic acid; mesalamine), to the colon while avoiding the adverse effects associated with the use of a sulfapyridine carrier. As a prodrug, olsalazine is an effective oral treatment for both active ulcerative colitis and for maintenance of disease remission and may possibly be of benefit in patients with Crohn's colitis. Findings from both short and long term noncomparative and comparative studies demonstrate that olsalazine 1 to 3g daily in divided doses improves clinical signs and symptoms of colitis in approximately 60 to 80% of patients with acute ulcerative colitis of mild to moderate severity. This improvement rate was similar to that obtained with sulfasalazine. Lower doses of olsalazine, usually 1g daily in divided doses, also maintained remission in patients with chronic ulcerative colitis. While olsalazine effectively delivers mesalazine to the colon, the prodrug itself increases net luminal water secretion and accelerates gastrointestinal transit of a meal. The resulting diarrhoea (occurring in approximately 17% of patients and resulting in withdrawal from therapy in 6% of patients) is distinguishable from that associated with inflammatory bowel disease by the high water content and the absence of blood. Olsalazine-induced diarrhoea usually occurred soon after initiation of olsalazine therapy or dosage increase, was more frequent with higher doses and was usually transient. Dosage reduction, increases in frequency of dosing and concomitant administration with food reduced the severity in many patients with persistent olsalazine-induced diarrhoea. With the exception of diarrhoea, olsalazine was generally well tolerated. Fewer than 14% of patients allergic to or intolerant of sulfasalazine had similar reactions to olsalazine. Olsalazine appears to be a suitable therapy for the treatment of first attacks as well as acute exacerbation of mild to moderate acute ulcerative colitis, and for the maintenance of remission in patients with chronic ulcerative colitis.

Inflammatory bowel disease revisited: newer drugs

The development of new drug therapy is an evolutionary process progressing from clinical success with current treatments through an understanding of interactions in the immune and inflammatory events that culminate in the tissue injury of IBD. The basic immunoinflammatory response is reviewed, with identification of the recognized and potential sites of activity of current therapies. Potential sites and implications for future interventions by newer therapies are discussed as we anticipate the discovery of the etiology and eventual cure for ulcerative colitis and Crohn's disease.