Ulcerative colitis and Crohn's colitis: differential diagnosis and treatment

Simple and simultaneous determination of sulphapyridine and acetylsulphapyridine in human serum by column-switching high-performance liquid chromatography

OBJECTIVE

A high-performance liquid chromatography (HPLC) with an automated on-line column-switching system was used for the simultaneous determination of sulphapyridine and acetylsulphapyridine, two major active metabolites related to the adverse effects of sulphasalazine, in human serum.

METHODS

Serum samples were directly injected into the HPLC, with the valve automatically switched on to remove serum proteins and other hydrophilic components remaining in the pre-column after elution of sulphapyridine and acetylsulphapyridine to the analytical column.

RESULTS

Serum proteins did not interfere with the analysis of either compound. The recoveries of SLP and Ac-SLP from drug-free human serum were 93.03-99.18% and CV were 2.88-4.34%. The within-run reproducibility of assays was excellent with relative standard deviations (RSD) of 1.01-3.90% (SLP) and 0.77-5.56% (Ac-SLP). The limit of quantification of sulphapyridine and acetylsulphapyridine was 3.13 microg/mL and 0.50 microg/mL, respectively. The serum concentrations in a patient with ulcerative colitis, who took 1.0 g sulphasalazine twice daily, were 31.20 microg/mL for sulphapyridine and 14.64 microg/mL for acetylsulphapyridine at 7 h after ingestion.

CONCLUSION

The present simple and reproducible assay was useful for the monitoring of serum sulphapyridine and acetylsulphapyridine.

Simultaneous determination of sulfasalazine and its metabolites sulfapyridine and N-acetylsulfapyridine in human serum by ion-pair high-performance liquid chromatography using a polymer-based column

An HPLC method is described for the simultaneous and rapid determination of sulfasalazine (salicylazosulfapyridine) and two of its metabolites, sulfapyridine and N-acetylsulfapyridine, in human serum. The range of quantitation is 0.1 to 12 micrograms/mL for sulfasalazine and sulfapyridine and 0.25 to 12 micrograms/mL for N-acetylsulfapyridine. Serum is mixed with acetonitrile containing the internal standard sulfamethazine and the ion-pairing agent tetraethylammonium chloride. The acetonitrile extract is concentrated and analyzed by HPLC, using a new polymer-based column, and detected by UV spectroscopy at 270 nm. This paper is the first both to describe the simultaneous analysis of all three of the compounds from serum and to present sulfasalazine concentration-time data following oral administration to humans.

Clinical pharmacokinetics of sulphasalazine, its metabolites and other prodrugs of 5-aminosalicylic acid

There is accumulating clinical evidence that 5-aminosalicylic acid (5-ASA) represents the therapeutic moiety of sulphasalazine in the treatment of inflammatory bowel disease. For more than 4 decades, the active metabolite, 5-ASA, has been administered in the form of the 'prodrug' sulphasalazine; however, in contrast to sulphasalazine, the pharmacokinetics of 5-ASA were unknown until recently. Sulphasalazine itself is poorly absorbed (3 to 12%) and its elimination half-life of about 5 to 10 hours is probably affected by the absorption process. The major part of sulphasalazine is split by bacterial azo-reduction in the colon into 5-ASA and sulphapyridine, the latter accounting for most of the adverse effects of sulphasalazine. The effective cleavage of sulphasalazine depends on an intact colon and transit time. It is markedly reduced in patients taking antibiotics and after removal of the large bowel. The formed sulphapyridine is almost completely absorbed and eliminated by hydroxylation, glucuronidation and polymorphic acetylation. Depending on the genetic phenotype, the elimination half-life and apparent oral clearance of sulphapyridine are approximately 14 hours and 40 ml/min (slow acetylators) or 6 hours and 150 ml/min (fast acetylators), respectively. Of the 5-ASA released from its 'vehicle' sulphapyridine in the colon, at least 25% is absorbed and after acetylation is subsequently excreted in the urine. At least 50% is eliminated in the faeces. Recently, 5-ASA has also been administered directly in the form of enemas, suppositories and oral slow-release preparations. While the elimination half-life of 5-ASA is short (0.5 to 1.5 h), its major acetylated metabolite (which may be active) exhibits a half-life of 5 to 10 hours. During therapy with sulphasalazine or 5-ASA, steady-state plasma concentrations of 5-ASA are relatively low (less than or equal to 2 micrograms/ml); thus its mode of action appears to be topically rather than systemically. Another approach to deliver the active 5-ASA to the gastrointestinal tract is accomplished with novel 'prodrugs' of 5-ASA, in which the carrier molecule sulphapyridine is replaced by 5-ASA itself (azodisalicylate) or other compounds.

Therapeutic efficacy of sulfasalazine and its metabolites in patients with ulcerative colitis and Crohn's disease

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.