Determination of sulfapyridine and its major metabolites in plasma by high pressure liquid chromatography

Increased oro-cecal transit time in grade I or II hepatic encephalopathy

The pathogenic mechanisms of hepatic encephalopathy remain to be elucidated. It has been suggested that a digestive motor disorder could promote the absorption of toxins produced within the lumen and thus enhance hepatic encephalopathy.

AIM

To evaluate oro-cecal transit time in cirrhotic patients with and without hepatic encephalopathy.

METHODS

Hospitalized patients with alcoholic cirrhosis without encephalopathy and with spontaneous grade I and II encephalopathy were included. Severity of hepatic encephalopathy was assessed clinically and the Child-Pugh score was used to describe cirrhosis severity. Nine healthy volunteers constituted a control group. Oro-cecal transit time was measured with the sulfasalazine test.

RESULTS

Twenty-eight patients (mean age 62.5 +/- 8.5 years) were included. Ten had hepatic encephalopathy of unknown cause and 18 were free of hepatic encephalopathy. Oro-cecal transit time was significantly longer in patients with hepatic encephalopathy (641 +/- 350 min) compared to patients without hepatic encephalopathy (298 +/- 96; P<0.05) and to controls (354 +/- 90; P<0.05). Oro-cecal transit time was comparable for each Child-Pugh score and was not different between the two grades of hepatic encephalopathy.

CONCLUSION

Oro-cecal transit time is longer in alcoholic cirrhosis patients with hepatic encephalopathy. This digestive motor disorder provides a partial explanation of hepatic encephalopathy of unknown etiology.

Fluorescence spectroscopy studies on 5-aminosalicylic acid and zinc 5-aminosalylicylate interaction with human serum albumin

The interaction between 5-aminosalicylic acid (5-ASA) or zinc 5-aminosalylicylate (5-ASZ) and human serum albumin (HSA) was studied by fluorescence spectroscopic technique. The binding constants of 5-ASA or 5-ASZ with HSA were determined at different temperatures under the optimum conditions. The binding sites were obtained and the acting force were suggested to be mainly hydrophobic. The effect of common ions on the binding constants was also investigated. A fluorescence spectroscopy assay of the proteins is presented in the paper. The determination results of the proteins in human serum by this method are very close to those obtained using Coomassie Brilliant Blue G-250 colorimetry, with relative standard deviations of 0.8-2.9%. A practical method was proposed for the determination of 5-ASA or 5-ASZ in human serum samples.

Simple method for the determination of 5-aminosalicylic and N-acetyl-5-aminosalicylic acid in rectal tissue biopsies

We describe a sensitive high-performance liquid chromatographic method for the determination of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid in rectal tissue biopsies. Samples were derivatised using propionic anhydride and proteins were precipitated with methanol. A Supelcosil ABZ column (150x4.6 mm I.D., 5 microm silica particles) was used with a mobile phase comprising 0.1 M acetic acid, acetonitrile and triethylamine (1600:114:6, v/v/v). Fluorescence detection was employed and detection limits were 0.2 ng/mg tissue at a signal-to-noise ratio of three (measured concentration: 5-aminosalicylic acid, 0.254 (0.228-0.286) ng/mg, C.V. 10.7%; N-acetyl-5-aminosalicylic acid, 0.18 (0.154-0.198) ng/mg, C.V 9.8%). This assay was validated for use with serum, urine and faecal samples for which it proved to be both precise and accurate (C.V.<10%, measured concentration within 10%).

Direct and metabolism-dependent toxicity of sulphasalazine and its principal metabolites towards human erythrocytes and leucocytes

1. The role of metabolites in sulphasalazine-mediated toxicity has been investigated in vitro by the use of human red blood cells and mononuclear leucocytes as target cells, with methaemoglobin formation and cytotoxicity respectively, being the defined toxic end-points. 2. Of the metabolites of sulphasalazine investigated, only sulphapyridine was bioactivated by human liver microsomes in the presence of NADPH to a metabolite which caused marked methaemoglobinaemia and a small, but statistically significant degree of mononuclear leucocyte cell death. 3. Methaemoglobinaemia was inhibited by ketoconazole but not by ascorbic acid (100 microM), glutathione (500 microM) and N-acetylcysteine (50 microM). In contrast, ascorbic acid and the thiols afforded complete protection for mononuclear leucocytes. 4. Sulphapyridine (100 microM) was converted in vitro to a metabolite (metabolite conversion 6.8 +/- 0.3%), the retention time of which on h.p.l.c. corresponded to synthetic sulphapyridine hydroxylamine. The half-life of sulphapyridine hydroxylamine in phosphate buffer (pH 7.4) was found to be 8.1 min. 5. In the absence of microsomes and NADPH, sulphapyridine hydroxylamine caused a concentration-dependent (10-500 microM) increase in methaemoglobinaemia (2.9%-24.4%) and cytotoxicity (5.4%-51.4%), whereas sulphasalazine, sulphapyridine, 5-hydroxy sulphapyridine and 5-aminosalicylic acid had no effect.

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.

Simple and rapid method for the simultaneous determination of the eight main metabolites and conjugates of sulphasalazine in human plasma, urine and faeces using dynamically modified silica

A simple and rapid method for the simultaneous determination of sulphapyridine, N-acetylsulphapyridine, 5-aminosalicylic acid, N-acetyl-5-aminosalicylic acid, hydroxysulphapyridine, N-acetylhydroxysulphapyridine, sulphapyridine O-glucuronide and N-acetylsulphapyridine O-glucuronide in plasma, urine and faeces is presented. After precipitation of plasma proteins by addition of methanol the samples are injected directly into the liquid chromatographic system. The limit of detection is 1 microgram/ml or less at a signal-to-noise ratio of 5 for all compounds using ultraviolet, fluorescence or electrochemical detection. The advantages of the dynamically modified silica approach in this reversed-phase high-performance liquid chromatographic method are demonstrated with respect to regulation and reproducibility of the selectivity.

Determination of salicylazosulphapyridine, sulphapyridine and its metabolites in serum and urine

Methods for the determination of salicylazosulphapyridine (Salazopyrin(R)), sulphapyridine, N-acetylsulphapyridine, sulphapyridine-O-glucuronide and N-acetylsulphapyridine-O-glucuronide in serum and urine have been developed. In one method samples were diluted with methanol to precipitate proteins present and thereafter injected directly onto the liquid chromatographic column. The sulphapyridine-O-glucuronide could not be determined by this method. For the determination of all the main sulphapyridine metabolites the sulphapyridine aglycones were formed after treatment with beta-glucuronidase. These sulphapyridine compounds were then extracted with isobutylmethyl ketone at pH 5, and re-extracted to a phosphate buffer at pH 13 prior to injection. Separation and retention of all compounds was affected both by pH and concentration of methanol in the mobile phase. The proposed method made determinations down to 1 mug ml(-1) possible, which was found to be sufficient. Comparisons were made with spectrophotometric methods.

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.

Sulfones and sulfonamides in dermatology today

Although dapsone and sulfapyridine have been used for years in dermatology, there has not always been a clear understanding of how these agents work. Recent investigation, however, has shed new light on thes agents which now allows a more rational approach to their use. This review is an attempt to familiarize the clinician with how these agents work, in what disease states they are effective, how to administer them, what adverse effects may occur, and how to monitor the patient to detect these adverse effects.