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Effect of olsalazine on sodium-dependent bile acid transport in rat ileum.

Olsalazine (OLZ), a relatively new form of 5-aminosalicylic acid (5-ASA), is being used for the treatment of colitis. A major side effect of olsalazine is diarrhea, reported in 12-25% of patients. One suggested mechanism for this side effect is enhanced ileal water and electrolyte secretion. We propose that OLZ may also inhibit ileal bile acid (BA) transport, resulting in choleretic diarrhea. This would result in excess BAs reaching the colon, with consequent BA-induced secretory diarrhea. Therefore, we studied the effect of OLZ on rat ileal absorption of taurocholate. BA uptake was determined in rat ileal segments, everted sacs, brush border membrane vesicles (BBMV), and Xenopus laevis oocytes. Segments and everted sacs were treated with 5 mM OLZ for 30 min prior to and throughout 10-min taurocholate (Tc) uptake. Terminal ileal BBMV were used to study the effect of OLZ on sodium-dependent bile acid uptake independent of cellular metabolism. Direct effects on the bile acid carrier were examined using Xenopus laevis oocytes expressing the cloned apical rat ileal BA transporter. In ileal segments 5 mM OLZ inhibited 10-min Tc uptake by 69.4 +/- 8.8% (P < 0.01) (N = 10 animals). Increasing concentrations of OLZ resulted in a dose-dependent inhibition of Tc uptake. Ten-minute Tc uptake with 0.5, 1.0, 2.0, 2.5, and 5 mM OLZ was inhibited by 13.5, 39.6, 49.7, and 70.5%, respectively. In BBMV, OLZ inhibited 45-sec Tc uptake in a dose-dependent manner but did not effect Na-dependent L-alanine uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminosalicylic Acids↗

Steady state disposition of 5-aminosalicyclic acid following oral dosing.

In 18 healthy volunteers the steady state disposition of 5-aminosalicylic acid (5-ASA, mesalazine, CAS 89-57-6; 500 mg tid) was evaluated following the last oral dose in form of slow release tablets (Salofalk) either containing 500 mg or 250 mg 5-ASA. In none of the pharmacokinetic parameters of 5-ASA characterizing bioavailability (e.g. AUC approximately 6 ug/ml x h; Cmax approximately 1.7 micrograms/ml; tmax approximately 5 h; Cminss approximately 0.5 micrograms/ml; Cavss approximately 0.75 microgram/ml) differences between both forms were observed and the calculated 90% confidence intervals and point estimates indicated bioequivalence. Following the delayed absorption 5-ASA was rapidly eliminated (t1/2 = 1.4 +/- 0.5 h).

Administration, Oral↗

5-Lipoxygenase inhibitors for the treatment of inflammatory bowel disease.

The unique role of the enzyme 5-lipoxygenase (5-LO) in the production of leukotrienes (LTs) makes it a likely target for biochemical manipulation. The rationale for using 5-LO inhibitors for the treatment of inflammatory bowel disease (IBD) is based on the increased generation of LTs in the inflamed mucosa, LTB4 being the most potent chemotactic and chemokinetic metabolite of arachidonic acid. Furthermore, conventional drugs, such as corticosteroids, sulphasalazine, and 5-aminosalicylic acid, inhibit LT production and specific 5-LO inhibition accelerates healing in animal models of acute colitis. The compounds identified as 5-LO inhibitors can be divided into antioxidants, substrate-analogous, and a large miscellaneous group of inhibitors, where hydroxamic acids are potent and more selective inhibitors of 5-LO. The benzothiophene hydroxyurea, zileuton, is the first selective 5-LO inhibitor evaluated for the treatment of patients with IBD. An 800-mg oral dose of zileuton was shown to reduce LTB4, but not prostaglandin E2, concentrations by 75-85% in rectal dialysates from patients with active ulcerative colitis. The clinical efficacy of zileuton 800 mg b.i.d. has also been tested in a randomized, double-blind, placebo-controlled trial in similar patients. Zileuton significantly improved the symptom scores and the histology score, but not the sigmoidoscopy score, compared to pretreatment conditions and with response to placebo, the beneficial effects being most pronounced in patients not receiving concomitant sulphasalazine treatment. The mean inhibition of LTB4 in the target tissue of inflammation was 70%. The proof that any putative 5-LO inhibitor is blocking LT production is an important stage in assessing any such drug. The main disadvantage of existing new LT inhibitors relates to the high potency of LTs, and unless a higher level of inhibition can be achieved, endogenous LTs may still be present in sufficient amounts to produce their effects.

Adrenal Cortex Hormones↗

[Acute manifestations in Crohn disease and ulcerative colitis. Conservative treatment of acute situations].

Ulcerative colitis (UC) and Crohn's disease (CD) can lead to perforation, abscesses and peritonitis. In such cases conservative treatment should only be secondary to surgery, whereas intensive conservative treatment is needed from the very start in toxic megacolon. The decision to operate must be made within 24-48 h. Partial or complete intestinal obstruction is frequently encountered in CD patients if the ileum is involved. Prednisone treatment can sometimes reverse this condition when combined with parenteral nutrition. Treatment of acute exacerbations of UC and CD is essentially conservative and consists of salazosulfapyridine or 5-aminosalicylic acid and prednisone.

Acute Disease↗

5-amino salicylic acid absorption and metabolism in ulcerative colitis patients receiving maintenance sulphasalazine, olsalazine or mesalazine.

BACKGROUND: All 5-aminosalicylic acid (5-ASA) preparations are potentially nephrotoxic, but there has been concern that newer delivery systems may increase this risk, either because of altered absorption or altered metabolism. Previous studies of 5-ASA absorption and excretion have usually either been performed in healthy controls or have only examined short-term therapy. 5-ASA and N-acetyl-5-ASA have therefore been measured in blood samples, and N-acetyl-5-ASA in urine samples, from patients with ulcerative colitis on long-term maintenance with different 5-ASA preparations and compared with sensitive markers of renal damage. METHODS: Patients receiving mesalazine (Asacol) (n = 13), sulphasalazine (n = 12) or olsalazine (Dipentum) (n = 8), all at doses within the recommended range were studied. Six-hour and trough serum concentrations of 5-ASA and N-acetyl-5-ASA and 24-h urinary excretion of N-acetyl-5-ASA were measured by high-performance liquid chromatography. RESULTS: Absorption of 5-ASA, assessed as 24-h excretion of N-acetyl-5-ASA expressed as molar % of ingested dose, was greater in patients receiving mesalazine, 23.25 +/- 10.65% (mean +/- s.d.; n = 13), than those receiving sulphasalazine (11.16 +/- 10.52%, n = 12; P = 0.003) or olsalazine (9.70 +/- 3.89%, n = 8; P < 0.002). The ratio of 5-ASA: N-acetyl-5-ASA in the serum 6 h after dose was also greater with mesalazine (1.02 +/- 0.44, mean +/- s.d.) than sulphasalazine (0.54 +/- 0.44, P < 0.02) or olsalazine (0.38 +/- 0.44, P < 0.005). Urinary markers of tubular damage were increased in four of 33 patients, but showed no correlation with concentration of 5-ASA or N-acetyl-5-ASA in serum and N-acetyl-5-ASA in urine, nor with lifetime dose or average daily dose of 5-ASA. CONCLUSIONS: In patients with ulcerative colitis receiving maintenance 5-ASA therapy there was greater absorption and less acetylation of 5-ASA from mesalazine (Asacol) compared with sulphasalazine or olsalazine, but no evidence from this study that this resulted in increased nephrotoxicity.

Absorption↗

Response to treatment of microscopic colitis.

Microscopic colitis is a recently recognized cause of diarrhoea, predominantly affecting older women, but its response to treatment is poorly documented. This report reviews the response to treatment of 16 patients with microscopic colitis and provides evidence for the use of 5-aminosalicylic acid and corticosteroids.

Aminosalicylic Acids↗