We studied the therapeutic efficacy of sulfasalazine and its metabolites sulfapyridine and 5-aminosalicylic acid in nine patients with Crohn's disease and in 23 patients with ulcerative colitis. In a randomized, controlled trial, we treated 11 patients for six weeks with 1 g of sulfasalazine three times a day, seven patients with 0.5 g of sulfapyridine three times a day, and 14 patients with 0.5 g of 5-aminosalicylic acid suppositories three times a day. The clinical state of the disease was characterized by an activity index, quality of stool, and remission rate. In addition, we monitored plasma levels of sulfapyridine, 5-aminosalicylic acid, and their acetylated metabolites. The initial activity index (mean +/- S.D.) was significantly reduced by sulfasalazine (from 245 +/- 129 to 100 +/- 71; P < 0.001) and by 5-aminosalicylic acid (from 251 +/- 65 to 90 +/- 93; P < 0.0001), but sulfapyridine was without benefit. Stool quality was also improved by sulfasalazine (82 per cent of the cases) and by 5-aminosalicylic acid (79 per cent). The highest remission rate was achieved with 5-aminosalicylic acid (86 per cent), followed by sulfasalazine (64 per cent) and sulfapyridine (14 per cent). Our investigations show that 5-aminosalicylic acid is the active moiety of sulfasalazine and that this effective metabolite may be an alternative to sulfasalazine in inflammatory bowel disease.

There is accumulating clinical evidence that 5-aminosalicylic acid (5-ASA), a primary metabolite of sulfasalazine (SAS), represents the therapeutic active moiety of the azo-compound SAS in the treatment of chronic inflammatory bowel disease (IBD). Since it is presumed that 5-ASA acts from the lumen of the intestine, it is important to know how much 5-ASA is released from its special galenic formulations. After liberation of 5-ASA in the terminal ileum (only slow release oral preparations of 5-ASA) and colon (5-ASA suppositories and enemas), 5-ASA is only partly absorbed. A major part of this 5-ASA is presystemically eliminated, eg, N-acetylated during its first passage through the intestinal mucosa and liver. Mean steady state plasma levels of unchanged 5-ASA are rather low (range 0.02 to 1.2 microgram/ml) whereas those of Ac-5-ASA are always higher (range 0.1 to 2.9 micrograms/ml). This is due to the rapid elimination of 5-ASA (t1/2 = 0.4 to 2.4h) and the slightly slower renal excretion of the Ac-5-ASA (t1/2 = 6 to 9 h, renal clearance = 200 to 300 ml/min). The knowledge of the pharmacokinetic properties of 5-ASA from different drug formulations might contribute to a better understanding of its mode of action in IBD.

No abstract

The disposition of 5-aminosalicylic acid (5-AS), the therapeutically active metabolite of sulphasalazine (SZ), has been studied in patients with active inflammatory bowel disease, in patients with biliary tract disease and post-operative T-tube drainage, and in healthy volunteers. Subjects were treated 3 times a day either with 5-AS 0.5 g suppositories and a slow-release preparation or with SZ 1 g tid (equivalent to 5-AS 1.14 g/day). Plasma and urine concentrations of 5-AS and its acetylated major metabolite (AcAS) were monitored during one dosing interval. In a cross-over trial in 5 patients with ulcerative colitis no difference, was found in the dose-corrected mean (+/- SD) steady state plasma levels (Css) of 5-AS and AcAS between treatment with 5-AS suppositories (0.10 +/- 0.07 and 0.50 +/- 0.20 micrograms/ml, respectively) and SZ (0.12 +/- 0.14 and 0.67 +/- 0.14 micrograms/ml, respectively). Urinary excretion of total AS (5-AS + AcAS), too, was similar (192 +/- 70 and 179 +/- 79 mg/day) with both forms of treatment. The oral slow-release form of 5-AS produced slightly higher Css in 5 patients with Crohn's disease (5-AS 0.21 +/- 0.22 micrograms/ml; AcAS 0.83 +/- 0.40 micrograms/ml) and in 5 healthy volunteers (5-AS 0.28 +/- 0.14 micrograms/ml; AcAS 1.10 +/- 0.43 micrograms/ml). Urinary recovery of total AS averaged 20 +/- 6% (patients) and 27 +/- 10% (volunteers).(ABSTRACT TRUNCATED AT 250 WORDS)

Following a single oral dose of racemic ibuprofen 600mg the stereoselective disposition of its enantiomers was studied in 8 patients with moderate to severe cirrhosis. Compared with the elimination half-life (t1/2) of (-)-R- and (+)-S-ibuprofen in 8 healthy age-matched controls (1.7 +/- 0.3h and 1.8 +/- 0.5h, respectively), t1/2 was prolonged significantly (p < 0.045 and < 0.001, respectively) in patients with cirrhosis (t1/2 = 3.1 +/- 1.7h and 3.4 +/- 1.0h, respectively). Whereas the low amounts excreted unchanged into urine differed slightly in both groups studied, much less (p < 0.01) conjugated ibuprofen was recovered either as the R-enantiomer (0.9 +/- 0.4% vs 4.1 +/- 2.8% of the dose) or the S-enantiomer (6.4 +/- 2.5% vs 26.5 +/- 12.9% of the dose) in patients with cirrhosis. Metabolic inversion of the inactive (-)-R-ibuprofen to the active (+)-S-ibuprofen may be impaired in hepatic dysfunction since the normal ratio of areas under the curve (AUC) for R- and S-enantiomers (0.79 +/- 0.18) was significantly (p < 0.02) higher in patients with cirrhosis (1.10 +/- 0.28). In a second study, a single oral dose of 400mg (+)-S-ibuprofen was administered to 8 healthy volunteers and 8 patients with cirrhosis. Elimination of this enantiomer was slightly impaired as could be seen from the prolonged t1/2 (1.6 +/- 0.1h vs 2.6 +/- 0.5h; p < 0.001) and the increase in AUC (101 +/- 35 vs 144 +/- 41 mg/L.h; p = 0.041). In conclusion, in patients with liver disease, hepatic elimination of ibuprofen is impaired. This should be taken into consideration especially if the racemic drug is used. Direct administration of the active (+)-S-enantiomer seems to offer less vulnerable treatment.