Medications as a potential source of exposure to phthalates in the U.S. population

BACKGROUND

Widespread human exposure to phthalates, some of which are developmental and reproductive toxicants in experimental animals, raises concerns about potential human health risks. Underappreciated sources of exposure include phthalates in the polymers coating some oral medications.

OBJECTIVE

The objective of this study was to evaluate whether users of phthalate-containing medications have higher urinary concentrations of phthalate metabolites than do nonusers.

METHODS

We used publically available files from the National Health and Nutrition Examination Survey for the years 1999-2004. For certain survey periods, participants were asked to recall use of prescription medication during the past 30 days, and for a subsample of individuals, the urinary concentrations of phthalate metabolites were measured. We a priori identified medications potentially containing phthalates as inactive ingredients and then compared the mean urinary concentration of phthalate metabolites between users and nonusers of those medications.

RESULTS

Of the 7,999 persons with information on urinary phthalate concentrations, 6 reported using mesalamine formulations, some of which may include dibutyl phthalate (DBP); the mean urinary concentration of monobutyl phthalate, the main DBP metabolite, among these mesalamine users was 50 times higher than the mean for nonusers (2,257 microg/L vs. 46 microg/L; p < 0.0001). Users of didanosine, omeprazole, and theophylline products, some of which may contain diethyl phthalate (DEP), had mean urinary concentrations of monoethyl phthalate, the main DEP metabolite, significantly higher than the mean for nonusers.

CONCLUSION

Select medications might be a source of high exposure to some phthalates, one of which, DBP, shows adverse developmental and reproductive effects in laboratory animals. These results raise concern about potential human health risks, specifically among vulnerable segments of the general population and particularly pregnant women and children.

5-aminosalicylic acid release from a new controlled-release mesalazine formulation during gastrointestinal transit in healthy volunteers

BACKGROUND

Mesalazine (5-aminosalicylic acid, 5-ASA) containing formulations represent a cornerstone in the treatment of inflammatory bowel diseases. A novel formulation with an Eudragit L/S mixture coating has been developed to provide selective release of 5-ASA to the ileo-caecal region and the colon.

AIM

To determine the release of 5-ASA during the gastrointestinal transit.

METHODS

A single oral dose of mesalazine EC 500 mg gastroresistant tablets (Asamax) was administered to eight healthy male volunteers. Gastrointestinal transit and tablet disintegration were monitored by scintigraphy. 5-ASA release was verified by assessing plasma pharmacokinetics.

RESULTS

Initial tablet disintegration was observed 5.65 +/- 0.86 h after dosing, corresponding to the detection of 5-ASA in plasma. This occurred in the ileo-caecal region in three subjects and the ascending colon in the remaining five. The relative percentage of 5-ASA absorption was more pronounced in the ascending colon (41 +/- 27.4%) than the ileo-caecal region (6.6 +/- 9.2%).

CONCLUSION

This mesalazine EC gastroresistant tablets release locally active 5-ASA specifically in the ileo-caecal region and the ascending colon.

Adherence to treatment in inflammatory bowel disease

AIM

Adherence to therapy is important to ensure success. We wanted to explore this feature in patients with inflammatory bowel disease.

PATIENTS AND METHODS

We explored adherence to treatment and its modifiers in 40 patients with inflammatory bowel disease using a battery of tests.

RESULTS

A 67% of patients (95% CI: 51-81%) acknowledged a certain degree of involuntary nonadherence, and 35% (95% CI: 20-51%) of voluntary nonadherence. Overall, 72% (95% CI: 56-85%) of patients had some form of nonadherence. An objective correlation of these self-reported data was assessed by the determination of urine salicylate levels in the subset of patients treated with mesalazine or its derivatives (15 cases). Two of them (13%) had no detectable urinary drug levels, indicating complete nonadherence. Voluntary nonadherence was higher in patients with lower scores in the intestinal (p = 0.02) and social areas (p = 0.015) of IBDQ-32, as well as in those with less active Crohn s disease (p < 0.005), patients with high depression scores and high patient-physician discordance (p = 0.01), patients with long-standing disease (p = 0.057), patients who considered themselves not to be well informed about the treatment they were getting (p = 0.04) or who trusted their attending physicians less (p = 0.03).

CONCLUSIONS

Intentional nonadherence to therapy is prevalent among patients with inflammatory bowel disease. A correction of factors associated to poor adherence could lead to higher therapeutic success.

Combined scintigraphic and pharmacokinetic investigation of enteric-coated mesalazine micropellets in healthy subjects

BACKGROUND

There is a growing clinical trend to increase the daily dose of mesalazine, which leads to significant compliance issues associated with multiple dosings of current preparations.

AIM

To examine the gastrointestinal performance and systemic exposure of a 1.5 g sachet (micropellets) mesalazine formulation, compared with three enteric-coated tablets (500 mg each, Claversal).

METHODS

A randomized, two-way, cross-over pharmacoscintigraphic (scintigraphy plus pharmacokinetics) study and a two-way, cross-over, pharmacokinetic-only study were performed in 24 healthy volunteers (12 subjects per investigation).

RESULTS

The relative bioavailability of mesalazine was 92% comparing micropellets with Claversal tablets, and the cumulative urine excretion was c. 26% for both preparations, suggesting comparable systemic exposure for the two types of preparation. In the majority of subjects, drug release from the micropellet formulation occurred predominantly in the terminal ileum and ascending colon. The Claversal tablets disintegrated in comparable intestinal sites, albeit at slightly later time points than the micropellets, principally due to slower gastric emptying for the single-unit formulation.

CONCLUSION

The 1.5 g micropellet formulation offers comparable delivery properties to the marketed tablets, but with greater convenience of dosing.

Gastrointestinal transit and release of 5-aminosalicylic acid from 153Sm-labelled mesalazine pellets vs. tablets in male healthy volunteers

BACKGROUND

Mesalazine (5-aminosalicylic acid)-containing formulations, designed to optimize drug delivery to the ileo-caecal region, represent a cornerstone in the treatment of inflammatory bowel diseases.

AIM

: To test, by means of pharmaco-scintigraphy, whether novel mesalazine-containing pellets release 5-aminosalicylic acid in the same target region as mesalazine tablets (Salofalk).

METHODS

Fourteen healthy male volunteers received a single dose of either pellets or tablets containing 500 mg of mesalazine and 2 mg of 152Sm2O3 with a 1-week washout period. The gastrointestinal transit of 153Sm, incorporated into the formulations, was followed by gamma-scintigraphy. Mesalazine release was verified by assessing 5-aminosalicylic acid plasma pharmacokinetics.

RESULTS

The formulations reached the ileo-caecal target region almost at the same time (3.3 +/- 1 and 3.8 +/- 1 h for pellets and tablets, respectively). Plasma 5-aminosalicylic acid tmax values were comparable and corresponded to the time during which the formulations were located in the target region. Plasma AUC values were significantly lower for pellets, which might be explained by a more prolonged release of 5-aminosalicylic acid.

CONCLUSIONS

Novel mesalazine pellets and Salofalk tablets release active 5-aminosalicylic acid in the same target region and pass through the gastrointestinal tract under fasting conditions in healthy volunteers in a comparable time. From a comparison of in vitro dissolution and plasma concentration data, a slower and more prolonged release of 5-aminosalicylic acid from pellets is suggested.

Gastrointestinal transit and 5-ASA release from a new mesalazine extended-release formulation

BACKGROUND

Mesalazine (5-aminosalicylic acid, 5-ASA)-containing formulations represent a cornerstone in the treatment of inflammatory bowel diseases. Recently, a new formulation has been developed to provide selective and more homogeneous release of 5-ASA compared to traditional systems.

METHODS

In a first study, gastrointestinal transit was followed by gamma-scintigraphy after single-dose application of tablets containing 1200 mg mesalazine to 12 healthy male volunteers. 5-ASA release was verified by the assessment of plasma pharmacokinetics. In a second, 7-day, multiple-dose study, the steady state plasma pharmacokinetics, urinary excretion and safety profile were characterized after twice-daily tablet administration to 12 healthy volunteers.

RESULTS

Tablet erosion started after 6.9 +/- 1.1 h in the ascending or transverse colon. Radioactivity spread homogeneously throughout the colon, indicating the sustained release of active 5-ASA. Plasma kinetics indicated an earlier initial absorption of 5-ASA, i.e. during transit of the small intestine and ileum. Mean Cmax values (350.6 +/- 322.6 ng/mL) were observed during location in the ileo-caecal region. The mean relative absorption of 5-ASA was 19.9 +/- 18.2% in the small intestine and ileum and 80.1 +/- 18.2% in the colon.

CONCLUSIONS

The administration of the new mesalazine formulation was well tolerated, and 5-ASA was continuously released along the whole colon, a favourable prerequisite for the therapy of distally located inflammatory bowel disease.

Systematic review: the pharmacokinetic profiles of oral mesalazine formulations and mesalazine pro-drugs used in the management of ulcerative colitis

AIM

: To quantify through systematic review the pharmacokinetic profiles of the oral delayed release and sustained release mesalazine (5-aminosalicylate, 5ASA) formulations (Asacol, Salofalk, Mesasal, Claversal, Pentasa) and pro-drugs (sulfasalazine, olsalazine, balsalazide) used in the management of ulcerative colitis.

METHODS

: Selected articles had: (1) adult healthy volunteers or patients with ulcerative colitis and (2) quantification of pharmacokinetic data to include, at a minimum, urinary excretion of total 5ASA [5ASA plus N-Acetyl-5ASA (N-Ac-5ASA)].

DATA COLLECTION AND ANALYSIS

: Pharmacokinetic data (Tmax, Cmax, AUC, urinary excretion, faecal excretion) of 5ASA, its major metabolite N-Acetyl-5ASA, total 5ASA, and the parent pro-drug compounds was extracted.

MAIN RESULTS

: The summary results for urinary excretion of total 5ASA over 24-96 h in all subjects (either mean or median) were: sulfasalazine mean 11-33% or median 22%; olsalazine mean 14-31% or median 16-27%; balsalazide mean 12-35% or median 20%; Asacol mean 10-35% or median 18-40%; Pentasa mean 15-53% or median 23-34%; Salofalk, Mesasal and Claversal mean 27-56% or median 31-44%. The summary results for faecal excretion of total 5ASA over 24-96 h in all subjects (either mean or median) were: sulfasalazine mean 23-75% or median 38%; olsalazine mean 47-50% or median 17-36%; balsalazide mean 46% or median 22%; Asacol mean 40-64% or median 20-56%; Pentasa mean 12-51% or median 39-59%; Salofalk, Mesasal and Claversal mean 37-44% or median 23-35%.

CONCLUSIONS

: The systemic exposure to 5ASA, as measured by urinary excretion of total 5ASA, and the faecal excretion of total 5ASA is comparable for all oral mesalazine formulations and pro-drugs. Thus, selection of a mesalazine therapy for the treatment of ulcerative colitis should be based on other factors such as efficacy, dose-response, toxicity of the parent compound and its metabolites, compliance issues related to dose forms and dosing schedules, and costs.

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.

Low dose balsalazide (1.5 g twice daily) and mesalazine (0.5 g three times daily) maintained remission of ulcerative colitis but high dose balsalazide (3.0 g twice daily) was superior in preventing relapses

BACKGROUND

Balsalazide is a new 5-aminosalicylic acid (5-ASA) containing prodrug. Its efficacy in comparison with standard mesalazine therapy and the optimum dose for maintaining remission of ulcerative colitis are still unclear.

AIMS

To compare the relapse preventing effect and safety profile of two doses of balsalazide and a standard dose of Eudragit coated mesalazine.

METHODS

A total of 133 patients with ulcerative colitis in remission were recruited to participate in a double blind, multicentre, randomised trial: 49 patients received balsalazide 1.5 g twice daily, 40 received balsalazide 3.0 g twice daily, and 44 received mesalazine 0.5 g three times daily. Efficacy assessments were clinical activity index (CAI) and endoscopic score according to Rachmilewitz, and a histological score. In addition, laboratory tests were performed and urinary excretion of 5-ASA and its metabolite N-Ac-5-ASA was analysed. The study lasted for 26 weeks.

RESULTS

Balsalazide 3.0 g twice daily resulted in a significantly higher clinical remission rate (77.5%) than balsalazide 1.5 g twice daily (43.8%) and mesalazine 0.5 g three times daily (56.8%) (p=0.006). The respective times to relapse were 161 days, 131 days (p=0.003), and 144 days (NS). Accordingly, pairwise contrasts of the final endoscopic score demonstrated a significant difference (p=0.005) between the two balsalazide treatment groups while differences between either of these two groups and mesalazine were not statistically significant. Patients treated with balsalazide excreted less 5-ASA and N-Ac-5-ASA than patients receiving mesalazine but these differences were not statistically significant. Discontinuation of the trial because of adverse effects occurred in nine patients: three in the balsalazide 1.5 g twice daily group, two in the balsalazide 3.0 g twice daily group, and four in the mesalazine 0.5 g three times daily group. No clinically important new drug safety related findings were identified in this study.

CONCLUSIONS

High dose balsalazide (3.0 g twice daily) was superior in maintaining remission in patients with ulcerative colitis compared with a low dose (1.5 g twice daily) or a standard dose of mesalazine (0.5 g three times daily). All three treatments were safe and well tolerated.

Colon-specific prodrugs of 5-aminosalicylic acid: synthesis and in vitro/in vivo properties of acidic amino acid derivatives of 5-aminosalicylic acid

5-aminosalicyl-L-aspartic acid (5-ASA-Asp) and 5-aminosalicyl-L-glutamic acid (5-ASA-Glu) were synthesized and their properties as colon-specific prodrugs of 5-aminosalicylic acid (5-ASA) were investigated employing rats as test animals. Incubation of 5-ASA-Asp and 5-ASA-Glu with the homogenates of tissue and contents of stomach or small intestine released no 5-ASA, indicating that they were stable in this condition. Incubation of 5-ASA-Asp with the cecal contents released 5-ASA 37%, whereas 5-ASA-Glu released only 8% of the dose in 16 h. Plasma concentration of 5-ASA-Asp after intravenous administration decreased rapidly and became undetectable in 60 min. No 5-ASA was detected in the blood, which indicated 5-ASA-Asp was stable in the plasma. After oral administration of 5-ASA-Asp, concentration of 5-ASA, its metabolite N-acetyl-5-ASA, and 5-ASA-Asp in the plasma, feces, and urine was determined. In the plasma, 5-ASA-Asp was not detected and the concentration of 5-ASA or N-acetyl-5-ASA was very low. About 33% of the administered dose was recovered as 5-ASA and N-acetyl-5-ASA and 43% as 5-ASA-Asp from feces, and 20% as 5-ASA and N-acetyl-5-ASA and 1% as 5-ASA-Asp from urine in 24 h. These results suggested that most of 5-ASA-Asp was delivered to the large intestine and about half of the administered dose was activated to liberate 5-ASA. After oral administration of free 5-ASA, fecal recovery was only 7% of the dose in 24 h and more than 80% was recovered from urine. Comparing 5-ASA-Asp and free 5-ASA, the amount of 5-ASA available in the large intestine was much larger, while the amount of 5-ASA in urine, which might be related to the systemic toxicity of 5-ASA, was much lower by the administration of 5-ASA-Asp than free 5-ASA.

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.

Dose loading with delayed-release mesalazine: a study of tissue drug concentrations and standard pharmacokinetic parameters

AIMS

Tissue concentrations of 5-aminosalicylic acid (5ASA) and its metabolites may influence the clinical course of inflammatory bowel disease. Since the factors that determine tissue drug concentrations are unknown we have studied the relationships between the oral dose of delayed-release mesalazine, rectal tissue drug concentrations and standard pharmacokinetic parameters.

METHODS

Twelve healthy volunteers were studied following 7 days treatment with 1.2, 2.4 and 4.8 g of delayed-release mesalazine daily. 5-aminosalicylic acid and N-acetyl 5-aminosalicylic acid concentrations were measured in serum, urine, stool and rectal tissue biopsies.

RESULTS

Serum concentrations and 24 h urinary excretion of 5ASA and N-acetyl 5ASA increased as the oral dose of mesalazine was increased from 1.2 g through 2.4 g to 4.8 g daily (serum area under curve (AUC):5ASA = 3. 9, 15.4 and 46.8 microg ml-1 h, P < 0.0001; N-acetyl 5ASA = 17.2, 30. 9 and 57.8 microg ml-1 h, P < 0.0001: urinary excretion: 5ASA = 1.8, 85.5 and 445 mg, P < 0.0001; N-acetyl 5ASA = 250, 524 and 1468 mg, P < 0.0001, respectively). Faecal 5ASA excretion increased as the oral dose increased from 1.2 g to 2.4 g but did not increase further with 4.8 g daily dosing whereas faecal N-acetyl 5ASA excretion was similar at all three doses. Rectal tissue concentrations of 5ASA increased markedly, and N-acetyl 5ASA increased modestly, as the dose of oral mesalazine increased from 1.2 g to 2.4 g daily but neither increased further with 4.8 g daily dosing.

CONCLUSIONS

The relationship between the ingested dose of delayed-release mesalazine and rectal tissue drug concentrations is complex. Factors other than dose are likely to be important determinants of rectal tissue drug concentrations.

Validation of a LC method for the determination of 5-aminosalicylic acid and its metabolite in plasma and urine

The choice of a proper analytical method for the quantification of drugs and/or their metabolites in biological samples plays a significant role in the evaluation and interpretation of bioavailability, bioequivalence and pharmacokinetic data. The aim of this study was validation of a method for the identification and quantitative determination of 5-aminosalicylic acid (5-ASA) and its metabolite N-acetyl-5-aminosalicylic acid in human plasma and urine. According to previous studies on the disposition of 5-ASA (mesalazine) in a patient with inflammatory bowel diseases, we have developed a rapid, sensitive method for the determination of 5-ASA and its acetylated metabolite, N-acetyl-5-aminosalicylic acid (Ac-5-ASA). The advantage of this method is that it measures both compounds, and is more rapid, reproducible and credible than the previous studies [C. Fischer, K. Maier, U. Klotz, J. Chromatogr. Biomed. Appl. 225 (1981) 498-503; P.N. Shaw, A.L. Sivner, L. Aarons, J.B. Houston, J. Chromatogr. Biomed. Appl. 274 (1983) 393-397; B. Norlander, R. Gotthard, M. Strom, Aliment. Pharmacol. Ther. 3 (1989) 333-342; U. Klotz, G.L. Stracciari, Arzneim.-Forsch. Drug Res. II 43 (12) (1993) 1357-1359]. 5-ASA was quantitatively determined in human plasma and urine samples by liquid chromatography following prior derivatization to its acetylated metabolite (Ac-5-ASA). N-Acetyl-anthranilic acid was used as the internal standard. The detection was performed with a spectrofluorimetric detector, excitation at 311 nm, cut-off at 449 nm. The method was validated for the following parameters: linearity, recovery, sensitivity, precision, accuracy, selectivity and stability, limits of quantification and of detection. It showed good linearity (r2 > or = 0,996) in the range 0.1 ng/ml to 8 microg/ml using a Lichrospher 60 RP-select B column. The lower limit of detection was 20 ng/ml in plasma and urine. The within-run relative standard deviations (R.S.D.) were below 6.7% at all concentration levels and the between-run R.S.D. were below 25.4% at all concentration levels.

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%).