Nonadherence in inflammatory bowel disease: results of factor analysis

BACKGROUND

The purpose of the study was to assess overall nonadherence to treatment among patients with Crohn's disease (CD) and ulcerative colitis (UC) in a single tertiary center.

METHODS

A total of 177 patients were enrolled in this study (84 males, 93 females; 117 CD, 60 UC). Patients were interviewed about their nonadherent behavior and their answers were analyzed using factor analysis. Urine samples were collected from a subcohort of 47 patients treated by mesalamine to verify the presence of 5-ASA or its metabolites.

RESULTS

Overall intentional nonadherence was reported by 38.9% of patients; 18.6% of the patients discontinued the treatment at least once. Intentional dose reduction was reported by 18% of patients; 14.7% of patients occasionally did not refill their medications on time. There were no differences in adherence between males and females, disease type, previous bowel surgery, or marital, smoking, and nonsmoking status. More than 38% of patients reported unintentional nonadherence. Factor analysis proved that nonadherence increased with a higher education level of the patients and decreased with older age. Adverse drug effects strongly contributed to nonadherence. Nonadherent patients were more likely to be chronically active or in relapse (tau = 0.212; P = 0.002). In the group of 47 patients whose urine was analyzed, 6 cases (12.7%) were negative for mesalamine or its metabolite.

CONCLUSIONS

The overall intentional nonadherence with medical therapy is relatively high among IBD patients and should be taken into account when a patient's response to treatment is unsatisfactory. Therefore, problems of nonadherence should be discussed with all IBD patients.

Studies of compliance with delayed-release mesalazine therapy in patients with inflammatory bowel disease

BACKGROUND

Non-compliance with maintenance mesalazine therapy may be a risk factor for relapse in inflammatory bowel disease, but the prevalence and determinants of non-compliance are unknown.

AIM

To study the prevalence and determinants of non-compliance in patients with inflammatory bowel disease.

METHODS

Out-patients receiving delayed-release mesalazine were studied. Compliance was determined by direct enquiry and by analysis of urine samples for 5-aminosalicylic acid/N-acetyl-5-aminosalicylic acid. Potential determinants of compliance were assessed.

RESULTS

Ninety-eight patients were studied. Forty-two patients (43%) reported taking <80% of their prescribed dose. Logistic regression revealed the independent predictors of non-compliance to be three-times daily dosing [odds ratio (OR), 3.1; 95% confidence interval (CI), 1.8-8.4] and full-time employment (OR, 2.7; 95% CI, 1.1-6.9). Urine from 12 patients (12%) contained no detectable 5-aminosalicylic acid/N-acetyl-5-aminosalicylic acid, and 18 patients (18%) had levels below those expected. Depression was the only independent predictor of complete non-compliance (OR, 10.5; 95% CI, 1.8-79.0), and three-times daily dosing was the only independent predictor of partial non-compliance (OR, 3.7; 95% CI, 1.8-8.9). Self-reporting correctly identified 66% of patients judged to be non-compliant on urinary drug measurement.

CONCLUSIONS

Non-compliance with maintenance mesalazine therapy is common in patients with inflammatory bowel disease. Three-times daily dosing and full-time employment are predictors of partial non-compliance, whilst depression is associated with complete non-compliance. Self-reporting detects most non-compliant patients.

Intrarectal administration of 5-aminosalicylic acid to rabbits and dogs

Intrarectal administration of 5-aminosalicylic acid (5-ASA) to rabbits and dogs was performed to obtain safety data. Groups of rabbits and dogs received twice daily intrarectal doses of 250, 500 or 1000 mg 5-ASA for 14 consecutive days. Treatment had no adverse effect on the behaviour or performance of the animals and microscopic examination revealed no evidence of systemic or local toxicity.

Synthesis and in vitro/in vivo evaluation of 5-aminosalicyl-glycine as a colon-specific prodrug of 5-aminosalicylic acid

A simple synthetic route for the preparation of amino acid conjugate of 5-aminosalicylic acid (5-ASA) was exploited and prepared 5-aminosalicyl-glycine (5-ASA-Gly) in good yield. In vitro and in vivo properties of 5-ASA-Gly as a colon-specific prodrug of 5-ASA were investigated using rats as the test animal. Incubation of 5-ASA-Gly with cecal or colonic contents at 37 degrees C released 5-ASA in 65 or 27% of the dose in 8 h, respectively. No 5-ASA was detected from the incubation of 5-ASA-Gly with the homogenates of stomach or small intestine. Plasma concentration of 5-ASA-Gly decreased rapidly after intravenous administration of 5-ASA-Gly, and no 5-ASA was detected in the blood, which indicated 5-ASA-Gly was not degraded in the plasma. After oral administration of 5-ASA-Gly, about 50% of the administered dose was recovered as 5-ASA and N-acetyl-ASA and 3% as 5-ASA-Gly from feces and 14% as 5-ASA-Gly and 28% as 5-ASA and N-acetyl-ASA from urine in 24 h. These results suggested that a large fraction of 5-ASA-Gly was delivered to the large intestine and activated to liberate 5-ASA. For comparison, total recovery of 5-ASA and N-acetyl-5-ASA from feces after oral administration of 5-ASA-Gly was greater than that from sulfasalazine, which is one of the most commonly prescribed prodrugs of 5-ASA.

Systemic levels of free 5-aminosalicylic acid depend on the nature of the 5-aminosalicyclic acid derivative and not on disease activity or extent in patients with inflammatory bowel disease

INTRODUCTION

Several new derivatives of sulphasalazine that make use of its active moiety, 5-aminosalicylic acid (5-ASA), have been introduced for the treatment of inflammatory bowel disease (IBD). In rats short term intravenous administration of 5-ASA has been associated with nephrotoxicity. A number of cases of nephrotoxicity have been reported recently in IBD patients taking oral maintenance treatment with 5-ASA compounds.

OBJECTIVE

To study the urinary and serum levels of acetylated 5-ASA (Ac-5-ASA) and the unacetylated 5-ASA (5-ASA) in patients with IBD maintained on sulphasalazine, olsalazine and mesalazine (pH dependent release form). We also sought correlation between levels of 5-ASA, clinical disease activity and extent of disease.

METHODS

We studied 79 patients (male, n = 30; female, n = 49) with established IBD [ulcerative colitis (UC), n = 48; Crohn's disease (CD), n = 31], 72 maintained on 5-ASA compounds (sulphasalazine = 27; olsalazine = 28; mesalazine = 17) and 7 patients were receiving no medication. Urinary and serum analysis of 5-ASA was performed by high performance liquid chromatography (HPLC). Clinical disease activity was quantified using simple index of Harvey and Bradshaw.

RESULTS

Patients receiving mesalazine had significantly higher levels of serum free 5-ASA compared to those who were receiving olsalazine and sulphasalazine (mesalazine mean +/- SEM; range; 2.84 +/- 1.21 (0.00-16.00) vs olsalazine 0.45 +/- 0.18 (0.00-16.20); mumol/L; p < 0.04; sulphasalazine 0.37 +/- 0.25 (0.00-3.74); p < 0.03). Similarly levels of urinary free 5-ASA were significantly higher in patients maintained on mesalazine compared to those on olsalazine or sulphasalazine (mesalazine 219 +/- 80.43 (0.00-1050) vs olsalazine 33.3 +/- 17.23 (0.00-317) mumol/L; p < 0.01; and sulphasalazine 15 +/- 8.86 (0.00-192); p < 0.05). However, no significant difference was observed in the levels of urinary free 5-ASA between olsalazine and sulphasalazine. No significant difference was observed in the levels of free-5-ASA in UC patients with left sided disease and those with extensive disease. Furthermore, no significant difference was observed in the levels of serum and urinary 5-ASA in CD patients with ileo-colic disease and colonic disease. Urinary and serum free-5-ASA did not correlate with the clinical disease activity.

CONCLUSION

Systemic absorption of 5-ASA from sulphasalazine and olsalazine is relatively low. However, pH-dependent mesalazine formulations may release their contents rapidly in the small intestine and proximal colon resulting in higher plasma and urinary concentrations of free 5-ASA. The effects of free 5-ASA on renal function in the human require further evaluation.

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%).

Determination of p-aminosalicylic acid and its N-acetylated metabolite in human urine by capillary zone electrophoresis as a measure of in vivo N-acetyltransferase 1 activity

A capillary zone electrophoresis method has been developed for the determination of p-aminosalicylic acid (PAS) and its metabolite, N-acetyl-p-aminosalicylic acid (N-acetyl-PAS), in urine. A linear relationship was observed between time-normalized peak area and the concentration of the parent and metabolite with correlation coefficients greater than 0.9990. The method could be applied to the determination of PAS and N-acetyl-PAS in human urine without any sample pretreatment. A good separation of the analytes is achieved in a run time of 12 min (15 min total, including capillary wash). Using PAS as a probe for N-acetyltransferase 1 activity, 20 healthy volunteers were phenotyped after oral administration of a 1 g dose. The preliminary results seem to indicate a bimodal distribution of N-acetyl-PAS/PAS molar ratios.

Systemic absorption of 5-aminosalicylic acid in patients with inactive ulcerative colitis treated with olsalazine and mesalazine

OBJECTIVE

To compare the systemic load of 5-aminosalicylic acid (5-ASA) as a basis for potential long-term toxicity during treatment in usual dosage with olsalazine (Dipentum) and one controlled-release mesalazine preparation (Salofalk) in patients with inactive ulcerative colitis.

DESIGN

Open, randomized, crossover study. TREATMENT SCHEDULE: Olsalazine 500 mg twice daily for 7 days and mesalazine 500 mg thrice daily for 7 days consecutively.

PATIENTS

Fifteen patients (12 males/3 females) aged between 18-70 years with ulcerative colitis in endoscopically confirmed remission for at least one month.

METHODS

A morning predose plasma sample and a 24-h urine collection on days 6 and 7 of each course were obtained from all patients for quantitative determination of 5-ASA and acetyl-5-ASA (Ac-5-ASA) concentrations. High performance liquid chromatography was used and all analyses were performed blindly on coded samples.

RESULTS

Treatment with mesalazine compared with olsalazine gave significantly higher levels of 5-ASA and Ac-5-ASA in plasma and urine. Maximum values and ranges of all variables were higher in the mesalazine group than in the olsalazine group. It is noteworthy that there was clear discriminance in the range of urine 5-ASA and Ac-5-ASA concentrations after mesalazine and olsalazine treatment.

CONCLUSION

1. The mesalazine preparation used, in comparison with olsalazine given in usual dosages, causes significantly higher levels of 5-ASA and Ac-5-ASA in plasma and urine in patients with inactive ulcerative colitis. 2. The lower systemic load of 5-ASA may reduce the potential risk of adverse events and in particular of nephrotoxicity.

Systemic availability of 5-aminosalicylic acid: comparison of delayed release and an azo-bond preparation

AIM

To determine the systemic uptake of 5-aminosalicylic acid (5-ASA) and acetyl-5-ASA (Ac-5-ASA) at steady state during treatment with either an azo-bond preparation, olsalazine, or a delayed-release mesalazine.

METHODS

In an open cross-over trial with randomized sequence, 15 patients with ulcerative colitis in remission were given 7-day courses of olsalazine (Dipentum 1.0 g daily) and of mesalazine (Asacol 1.6 g daily). Plasma and urine were collected on days 6 and 7 of each course and concentrations of 5-ASA and Ac-5-ASA were determined by high-performance liquid chromatography (HPLC).

RESULTS

Mean steady-state plasma concentrations of 5-ASA and Ac-5-ASA were significantly higher after treatment with mesalazine than with olsalazine (P < 0.0001). Total urinary excretion of 5-ASA and Ac-5-ASA as a percentage of the given dose was significantly higher on mesalazine than on olsalazine (P < 0.01). Only two patients experienced, during the first 3 days of treatment with olsalazine, transient watery diarrhoea which resolved spontaneously. No unexpected or major changes in haematology or biochemistry were detected during the study.

CONCLUSION

As 5-ASA acts locally, the lower systemic load provided by olsalazine may increase efficacy and reduce the potential risk of nephrotoxicity during long-term maintenance treatment of ulcerative colitis.

Pharmacokinetics of 5-aminosalicylic acid from controlled-release capsules in man

One gram single dose of Pentasa controlled-release capsules was administered to 24 healthy volunteers under fasting condition. Mean plasma 5-aminosalicylic acid (5-ASA) and acetyl 5-ASA concentrations peaked at 0.53 microgram.ml-1 and 1.33 micrograms.ml-1 from 3 to 4 hours following dosing, respectively. The half-lives of both compounds could not be determined as absorption of 5-ASA was continuous throughout the gastrointestinal tract. An average of 29.4% (CV: 27%) of the dose was excreted in the urine primarily as acetyl 5-ASA. Up to 91.1% of the dose was released from the capsules. Forty percent of the dose (CV: 40%) was eliminated in the feces, with 8.9% of the dose remained as formulation bounded 5-ASA, indicating that controlled-release capsules continue to release drug throughout the GI tract. 5-ASA contributed 46.7% of the salicylates eliminated in the feces and acetyl 5-ASA accounted for the balance. Controlled-release capsules produced three times more total salicylates and 10 times more total and free 5-ASA in the feces than did 5-ASA suspension. Thus, while lower systemic levels of salicylates were absorbed, greater therapeutic quantities of 5-ASA were available in the bowel.

Delivery and fate of oral mesalamine microgranules within the human small intestine

BACKGROUND/AIMS

Oral use of mesalamine in inflammatory bowel disease requires slow-release preparations to prevent premature absorption and inactivation. Resulting luminal concentrations within the human small intestine are unknown. The aim of this study was to determine human intestinal delivery patterns of mesalamine from a microgranule preparation (Pentasa; Ferring Arzeimittel, Kiel, Germany) effective in Crohn's disease with small bowel involvement.

METHODS

A multilumen tube for duodenal, jejunal, and ileal aspiration and marker perfusion was placed in 6 normal subjects. Levels of luminal, plasma, and urinary mesalamine and its main metabolite, acetyl mesalamine, were measured for 7 hours after ingestion of mesalamine (500 mg) with a labeled meal.

RESULTS

Gastric emptying of mesalamine paralleled the meal, and its release occurred throughout the small intestine (cumulative, 20% of dose). For 4 hours, mean luminal mesalamine and acetyl mesalamine concentrations were 52 and 38 micrograms/mL (duodenum), 59 and 82 micrograms/mL (jejunum), and 64 and 104 micrograms/mL (ileum). Cumulative colonic delivery was 82% (7% dissolved, 75% in microgranules), and urinary excretion was 3.5%.

CONCLUSIONS

Although the major part of continuous-release mesalamine is delivered to the colon, large proportions are liberated and available at high concentrations within the small intestinal lumen, thus explaining its therapeutic efficacy in small intestinal Crohn's disease.

Pharmacokinetic studies of benzalazine

The pharmacokinetic properties of benzalazine ((2-hydroxy-5-[(4-carboxyphenyl)azo]benzoic acid, CAS 64896-26-0), a new agent for the treatment of ulcerative colitis and Crohn's disease of the large intestine, were investigated. From jejunal loops of rats in situ no noteworthy absorption of benzalazine was observed. All attempts to demonstrate metabolic conversion of benzalazine in mucosal homogenate of the small intestine of rats were without any success. In faecal suspensions, the half-life of the metabolic conversion of benzalazine was determined as 15 min and the formation of the metabolite 5-aminosalicylic acid (5-ASA) was demonstrated qualitatively. 72 h after single oral administration of 300 mg benzalazine/kg b.w. to rats, an average of 71.83% of the administered dose was recovered in urine and faeces. Only a small amount of unmetabolized benzalazine was excreted with urine and faeces (0.75% and 1.47% of the administered dose, respectively). The benzalazine metabolite 5-ASA and the 5-ASA metabolite acetyl-5-aminosalicylic acid (Ac-5-ASA) were excreted mainly with the faeces (29.22% and 20.66% of the administered dose, respectively) and only in small amounts with the urine (2.54% and 11.06% of the administered dose, respectively).

Brush-border-enzyme-mediated intestine-specific drug delivery. Amino acid prodrugs of 5-aminosalicylic acid

5-Aminosalicylic acid (5-ASA) is the active principle of a number of preparations aimed at the treatment of inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, but its efficacy is limited by early absorption and metabolism. The possibility to exploit the selective hydrolytic activity of brush border enzymes such as aminopeptidase A and carboxypeptidases was studied by preparing the following four amino acid prodrugs of 5-ASA: 5-(N-L-aspartylamino)-2-salicylic acid, disodium salt (18), 5-(N-L-glutamylamino)-2-salicylic acid, disodium salt (19), [(5-aminosalicyl)-L-prolyl]-L-leucine, sodium salt (25), and [[5-(N-L-glutamylamino)salicyl]-L-prolyl]-L-leucine, disodium salt (28). In these compounds, the peptide bond is selectively split by the intestinal brush border aminopeptidase A (compounds 18, 19, and 28) and carboxypeptidases (compounds 25 and 28).

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.

Identification of oxidation products of 5-aminosalicylic acid in faeces and the study of their formation in vitro

The formation of three oxidant-derived products of 5-aminosalicylic acid (5-ASA) in vivo was demonstrated in patients with active ulcerative colitis as well as in healthy subjects. The products were isolated from faeces by preparative HPLC and their chemical structures were found to be oxidation products of 5-ASA using 1H-NMR spectroscopy and mass spectrometry. Reactions carried out in vitro between 5-ASA and oxidants suggested to be present in the inflamed bowel verified that the hypochlorite-mediated oxidation of 5-ASA as well as the haemoglobin-catalysed H2O2-dependent oxidation of 5-ASA resulted in the formation of a single oxidation product of 5-ASA. This product was similar to, but not identical to any of the products identified in faeces from patients receiving 5-ASA. Oxygen radical-mediated oxidation of 5-ASA gave several products, different from the products isolated. Finally, it was verified that the products formed in vivo are not formed as a result of autooxidation of 5-ASA either in faeces extract or in pharmaceuticals.

Disposition of mesalazine from mesalazine-delivering drugs in patients with inflammatory bowel disease, with and without diarrhoea

The disposition of mesalazine from the azo compounds sulphasalazine and olsalazine (Dipentum) and from the slow-release mesalazine drugs Pentasa, Asacol, and Salofalk was studied in 20 patients with inflammatory bowel disease. Ten of them had diarrhoea, and 10 had normal stools. On the last 2 days of a 7-day maintenance treatment with each of the study drugs urine and faeces were collected for determination of mesalazine, acetyl-mesalazine, and unsplit azo compound. In patients with and without diarrhoea the urinary and the faecal excretion of acetyl-mesalazine was lowest during treatment with olsalazine. The proportion of acetyl-mesalazine in faeces was highest during treatment with Pentasa in both groups. The presence of diarrhoea was associated with a decrease in the proportion of acetyl-mesalazine in faeces during treatment with all drugs, not significant only for Pentasa. The proportion of unsplit azo compound in faeces increased in the case of diarrhoea to almost 50%. It is concluded that in patients with inflammatory bowel disease diarrhoea substantially influences the disposition from all these drugs except Pentasa.

A pharmacokinetic study of sulphasalazine and two new formulations of mesalazine

We have examined the pharmacokinetics of enteric coated sulphasalazine compared with two new formulations of mesalazine. These consisted of microgranules of mesalazine coated with Eudragit S in a concentration of either 20 or 25% dry lacquer substance; these in turn were enclosed in capsules coated with Eudragit L. In-vitro dissolution studies of coated microgranules showed that drug release was pH dependent. Studies in 7 normal volunteers showed median peak concentrations of 5-amino-salicylic acid and N-acetyl-5-amino-salicylic acid occurred at about 6 hours with both microgranular preparations, compared with sulphasalazine at 15 h. The microgranule formulation coated with 20% Eudragit S gave serum levels and overall systemic absorption similar to values with sulphasalazine. This new formulation may be of value for delivering mesalazine and other therapeutic agents to the colon.

High-performance liquid chromatographic assay of 5-aminosalicylic acid (5-ASA) and its metabolites N-beta-D-glucopyranosyl-5-ASA, N-acetyl-5-ASA, N-formyl-5-ASA and N-butyryl-5-ASA in biological fluids

A fast, highly sensitive high-performance liquid chromatographic method for the simultaneous determination of 5-aminosalicylic acid (5-ASA) and its metabolites N-beta-D-glucopyranosyl-5-ASA, N-formyl-5-ASA, N-acetyl-5-ASA and N-butyryl-5-ASA has been developed using a dynamically modified silica approach on a 40 mm x 4.6 mm I.D. column packed with 3-microns Hypersil. Plasma proteins are precipitated with acetonitrile. After extraction of the acetonitrile into 1,1,1-trichloroethane an undiluted aqueous phase containing the analytes is obtained. The detection limits are in the range 0.002-0.05 microgram/ml in plasma at a signal-to-noise ratio of 3 using fluorescence detection.

Steady-state pharmacokinetics of a new 4-gram 5-aminosalicylic acid retention enema in patients with ulcerative colitis in remission

The pharmacokinetic profile of a new 4-g 5-aminosalicyclic acid (5-ASA) retention enema, Mesasal, was investigated. Nine patients with ulcerative colitis in remission and one patient with mild disease activity received one enema for seven consecutive nights. They were admitted to hospital for administration of the eighth enema. Plasma concentration and urinary excretion of 5-ASA and acetyl-5-aminosalicyclic acid (Ac-5-ASA) were studied for 45 h and faecal excretion for 24 h after administration of the last enema. The median peak plasma concentration of 5-ASA was 0.92 (range, 0.59-1.87) micrograms/ml at a median of 11 h after administration, and of Ac-5-ASA 1.62 (range, 1.03-4.36) micrograms/ml at a median of 12 h after administration. On average, the plasma concentration of Ac-5-ASA was almost twice that of 5-ASA at each sampling period. At 24 h after administration the median plasma concentration for 5-ASA was 0.12 (range, 0-0.77) micrograms/ml and for Ac-5-ASA 0.36 (range, 0.01-1.6) micrograms/ml. At 45 h after administration low levels of both 5-ASA (less than 0.2 micrograms/ml) and Ac-5-ASA (less than 0.3 microgram/ml) were noted in two patients, low levels of only Ac-5-ASA (less than 0.1 microgram/ml) in two patients, and neither 5-ASA nor Ac-5-ASA in the other six patients. All patients had detectable urinary levels of both 5-ASA and Ac-5-ASA during the first 4 h after administration. Median urinary recovery during 45 h was 12.6% (range, 5.6-22.2%), indicating a low absorption at steady-state conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Disposition of 5-aminosalicylic acid by olsalazine and three mesalazine preparations in patients with ulcerative colitis: comparison of intraluminal colonic concentrations, serum values, and urinary excretion

To compare the disposition of 5-aminosalicylic acid (5-ASA) and its acetylated metabolite during treatment with olsalazine and mesalazine, 14 patients with inactive ulcerative colitis were randomly assigned to olsalazine (1 g twice daily) and the mesalazines, Asacol (800 + 400 + 800 mg daily), Pentasa (750 + 500 + 750 mg daily), and Salofalk (750 + 500 + 750 mg daily) in a crossover design trial so that all received each drug for seven days. Intraluminal colonic concentrations of 5-ASA were estimated after five days by the method of equilibrium in vivo dialysis of faeces. A predose serum sample and a 24 hour urine collection were obtained on day seven. The 5-ASA and acetyl-5-aminosalicylic acid (Ac-5-ASA) values were determined by high performance liquid chromatography. Olsalazine almost doubled the colonic concentrations (mean 23.7 (SEM) (1.9) mmol/l) of its therapeutically active ingredient (5-ASA) compared with equimolar doses of Pentasa (12.6 (2.2) mmol/l; p less than 0.0003) and Salofalk (15.0 (2.0) mmol/l; p less than 0.003). At the same time, olsalazine treatment was associated with lower serum concentrations and urinary excretions (p less than 0.05) of 5-ASA and Ac-5-ASA compared with the mesalazine preparations. The low systemic load of 5-ASA provided by olsalazine reduces the potential risk of nephrotoxicity during long term treatment.

Effect of food coadministration on 5-aminosalicylic acid oral suspension bioavailability

Single doses of 1 gm 5-aminosalicylic acid (5-ASA) suspension was administered to 24 healthy volunteers during both fasting and fed conditions. For subjects in a fasting state, plasma 5-ASA and acetyl 5-ASA concentrations peaked rapidly 1 hour after dosing to 14.72 micrograms/ml and 11.4 micrograms/ml, respectively. The elimination half-life of 5-ASA was 51.9 minutes, whereas the acetyl 5-ASA half-life could not be determined. A mean of 78.3% of the dose was excreted in the urine, with 5-ASA accounting for 21.2% of the dose and acetyl 5-ASA accounting for the balance. Only 11.3% of the dose was eliminated in the feces, consisting mostly of acetyl 5-ASA. Food coadministration reduced 5-ASA and acetyl 5-ASA systemic relative bioavailability to 44% and 76%, respectively, compared with the fasting treatment. Urinary excretion of the salicylates was reduced to 46.8%, and fecal salicylate elimination increased almost 100%--to 24.2% of the total dose.

Pharmacokinetics of sulfasalazine metabolites in rats following concomitant oral administration of riboflavin

Sulfasalazine, 60 mg/kg, was administered orally to groups of rats (n = 4) along with 1, 5, or 10 mg/kg of riboflavin. Plasma and urine were assayed for 5-aminosalicylic acid, acetyl-5-aminosalicylic acid, sulfapyridine, and acetyl-sulfapyridine using an HPLC method. The mean percent of dose recovered as total metabolites in urine was significantly greater (alpha = 0.01) for the group receiving 10 mg/kg riboflavin compared to the controls or the group receiving 1 mg/kg riboflavin. Plasma AUC and Cmax values were also significantly greater (alpha = 0.05) for the 10 mg/kg riboflavin group. These results suggest that at higher doses, a significant fraction of riboflavin reaches the colon intact and stimulates more efficient reduction of the azo bond in sulfasalazine. Since the concentrations of 5-ASA achieved in the colon may be directly related to the efficacy of sulfasalazine in treating inflammatory bowel disease, concomitant administration of riboflavin may enhance sulfasalazine's efficacy in humans.

Pharmacokinetics of a 5-aminosalicylic acid enteric-coated tablet and suppository dosage form

An Eudragit-L coated oral 5-aminosalicylic acid (5-ASA; mesalazine) product (Mesasal), has been formulated to deliver 5-ASA to the distal small intestine and colon for the treatment of inflammatory bowel disease. The purpose of this study was to compare the pharmacokinetic profile of this product to sulphasalazine (SASP; Salazopyrin) and to assess the pharmacokinetics of a suppository 5-ASA dosage form. Twelve healthy volunteers randomly received four single doses of 5-ASA delivering formulations not less than 1 week apart. (a) Mesasal tablets, 2 x 250 mg, fasting; (b) Mesasal tablets, 2 x 250 mg, fed; (c) Salazopyrin tablets, 3 x 500 mg (corresponding to 576 mg 5-ASA), fasting; and (d) Mesasal suppository, 1 x 500 mg, fasting. Plasma 5-ASA and acetyl-5-ASA (Ac-5-ASA) concentrations were followed for 48 h and urine and faecal concentrations for 72 h. Mesasal tablets (fasting) produced a greater area under the concentration-time curve (AUC), peak and time to peak for both plasma 5-ASA and Ac-5-ASA than Salazopyrin. Median urinary recovery values were 21.7% for Salazopyrin and 35.5% for Mesasal (fasting) (P less than 0.01). This means that the systemic absorption was higher after Mesasal than after Salazopyrin. The total faecal recovery values were 38.3 and 26.5%, respectively (NS). Except for a delay of 1.5-.3 h in the time to peak of 5-ASA and Ac-5-ASA plasma levels, the pharmacokinetics of Mesasal tablets were essentially the same in fasting or fed subjects. Suppository administration of 5-ASA resulted in a low median urinary recovery of 10.8%.

The pharmacokinetics of olsalazine sodium in healthy volunteers after a single i.v. dose and after oral doses with and without food

Olsalazine sodium (5,5'-azodisalicylic acid (OLZ] was given to eight healthy volunteers as a 10 mg i.v. bolus dose and as a 1 g oral dose with and without food. To five fasting participants single oral doses of 2 g and 4 g were given. Blood and urine were collected during three weeks after each dose and were assayed for OLZ, a conjugate identified as a sulphate of OLZ (OLZs), 5-aminosalicylic acid (5-ASA), and N-acetyl-5-aminosalicylic acid (ac-5-ASA). The study showed that: 1. OLZ had a very short elimination half-life, mean 56 min. 2. OLZ was absorbed from the intestinal tract to a very small extent, as seen from the low systemic availability and low urinary excretion, 2.3% and 0.31% respectively, for a 1 g dose taken fasting. 3. OLZ was present in the serum partly as a conjugate, which was identified as an O-sulphate. Following the i.v. dose the serum half-life of the O-sulphate was estimated to be 7 days. 4. Food intake did not influence the systemic availability of OLZ and ac-5-ASA. 5. There was no dose-dependent increase of OLZ absorption with single doses up to 2 g, but a 4-g dose showed a more than two-fold increase in the individual peak serum concentration and in the systemic availability of OLZ. However, there was no significant increase in the mean residence time (MRT) for OLZ or in the serum concentration of either 5-ASA or ac-5-ASA at a dose of 4 g.

Improved specificity of the PABA test with p-aminosalicylic acid (PAS)

Until now use of the PABA test together with [14C] PABA to calculate the PABA excretion index has probably been the best adaptation suggested to enhance the specificity of this non-invasive pancreatic function test. Drawbacks of the method are the application of radioactivity, the fact that children, pregnant women, and patients with renal insufficiency have to be excluded from the test, and the possible interference of drugs and isotopes. We propose simultaneous administration of p-aminosalicylic acid (PAS) in the PABA test and quantification of the urinary PABA and PAS excretion with liquid chromatography. Urinary PABA and PAS excretion in six hours are comparable (69.5 +/- 8.4% and 65.6 +/- 18.4% respectively in five healthy volunteers). Application of the PABA/PAS ratio was compared with the urinary PABA excretion in 21 normal controls, 38 patients with pancreatic disease, and 42 patients without pancreatic pathology. The PABA/PAS ratio and the per cent PABA excretion correlated very well in pancreatic patients: (PABA/PAS ratio) = 0.0149 (% PABA) + 0.052 (r = 0.902). Use of the PABA/PAS ratio enhanced the specificity of the test from 76 to 89%.

Metabolism and urinary excretion of 5-amino salicylic acid in healthy volunteers when given intravenously or released for absorption at different sites in the gastrointestinal tract

In six healthy subjects serum concentrations of 5 amino salicylic acid (5ASA) and acetyl 5ASA were measured for up to 24 hours, and urinary excretion over 48 hours. After an intravenous injection of 3.26 mmol 5ASA serum concentrations fell rapidly with a distribution half-life of 17 +/- 2 min and an elimination half-life of 42 +/- 5 min. After 45 minutes acetyl 5ASA became the dominant compound and after seven hours serum concentrations of both components were almost unrecordable. Orally ingested 5ASA in three preparations to ensure its release in the stomach, small intestine and ileocaecal region respectively gave lower serum concentrations and urinary excretion than those obtained after an intravenous infusion. Bioavailabilities which ranged from 19% for ileocaecal release to 75% for release in the upper gastrointestinal tract, were calculated from areas under the serum concentration curves. Urinary excretion of 5ASA and its acetyl metabolite over 48 hours was 78%, 52%, 55%, and 21% respectively of the dose given intravenously and orally for gastric, small intestinal and ileocaecal release.

A stable isotope method for the quantification of N-acetyl-5-aminosalicylic acid in plasma and urine

The synthesis of a number of N-acyl-5-aminosalicylic acids and their derivatives is described. These compounds allow the sensitive and specific mass spectrometric determination of unlabelled or deuterium-labelled N-acetyl-5-aminosalicylic acid in biological samples. An in vivo study shows that the labelled compound, administered to rats, is excreted isotopically unchanged to at least 97%, and that no significant deacetylation/acetylation mechanism exists for this metabolite N-acetyl-5-aminosalicylic acid of salicylazosulphapyridine.

Studies of two novel sulfasalazine analogs, ipsalazide and balsalazide

Sulfasalazine appears to exert its beneficial effect in colitis by releasing 5-aminosalicylic acid in the colon, but its use can be limited by side effects. Ipsalazide and balsalazide are novel sulfasalazine analogs designed to release 5-aminosalicylic acid and a nontoxic carrier molecule in the gastrointestinal tract. They have a low oral toxicity following single or repeat administration to mouse, rat, and ferret, and balsalazide is not mutagenic in the Ames test. Ipsalazide and balsalazide are split in rat and man, and the urinary and fecal excretion pattern of the 5-aminosalicylic acid released is similar to that of sulfasalazine; the carrier molecules are absorbed to a lesser extent than the sulfapyridine derived from sulfasalazine. These two analogs deserve therapeutic trial.

Influence of intestinal transit time on azo-reduction of salicylazosulphapyridine (Salazopyrin)

During a normal and an accelerated intestinal transit, in seven healthy volunteers, the recoveries of salicylazosulphapyridine (SASP) and its split products sulphapyridine (SP) and 5-aminosalicylic acid (5-ASA) were determined in urine and faeces. The azo-reduction of SASP and consequently the recovery of 5-ASA in the faeces was found to be substantially decreased during an accelerated intestinal transit. In addition, in 18 patients with inflammatory disease of the colon during maintenance therapy of SASP it could be demonstrated that the serum SP levels were related to the diarrhoeal state and did not correlate with disease activity. As recent studies have reported that 5-ASA is possibly the active therapeutic moiety of SASP, the ineffectiveness of SASP therapy in patients with active colitis may be ascribed to the reduced azo reduction of SASP as the result of profuse diarrhoea.

Colorimetric determination of 5-aminosalicylic acid and its N-acetylated metabolite on urine and feces

A simple and convenient colorimetric method is described for the quantitative determination of 5-aminosalicylic acid (5-ASA) and N-acetyl-5-ASA in urine and feces after oral administration of salicylazosulfa-pyridine (SASP), the drug of choice in the treatment of ulcerative colitis. N-acetyl-5-ASA is extracted directly from the acidified biological specimen, deacetylated, and the liberated 5-ASA subjected to a modified Bratton-Marshall reaction. The 5-ASA present in the specimen must be acetylated with acetic anhydride prior to extraction. The violet colored product of the Bratton-Marshall reaction has a lambdamax of 560 nm and conforms to Beer's law over the concentration range of 0-70 umg/ml. Average recoveries (+/- S.D., N = 6) OF 5-ASA added to rat and human urine and rat fecal homogenates were 91.6 +/- 4.9%, 102 +/- 6.0%, and 71.0 +/- 4.8%, respectively. Interference by SASP and its sulfapyridine metabolities is negligible. As demonstrated, the colorimetric method is of sufficient sensitivity for application in most metabolic and pharmacokinetic studies conducted with SASP in laboratory animals and man.

Detection of para-aminosalicylic acid (PAS) in urine: a simple spot test

A simple spot test for the detection of PAS in urine has been described and its sensitivity compared with that of other methods such as the Ehrlich's reagent and the ferric chloride tests. In patients receiving 4 g. PAS the three methods gave similar results in urine specimens collected within eight hours. The new test is an inexpensive micro method which can easily be performed on a large scale. There is no reaction with sulfonamide or salicylic acid derivatives.