Disposition of 5-aminosalicylic acid by 5-aminosalicylic acid-delivering compounds

Exploring Different Strategies for Efficient Delivery of Colorectal Cancer Therapy

Colorectal cancer (CRC) is the third most common cancer and the fourth leading cause of cancer death in the world. Currently available chemotherapy of CRC usually delivers the drug to both normal as well as cancerous tissues, thus leading to numerous undesirable effects. Much emphasis is being laid on the development of effective drug delivery systems for achieving selective delivery of the active moiety at the anticipated site of action with minimized unwanted side effects. Researchers have employed various techniques (dependent on pH, time, pressure and/or bacteria) for targeting drugs directly to the colonic region. On the other hand, systemic drug delivery strategies to specific molecular targets (such as FGFR, EGFR, CD44, EpCAM, CA IX, PPARγ and COX-2) overexpressed by cancerous cells have also been shown to be effective. This review aims to put forth an overview of drug delivery technologies that have been, and may be developed, for the treatment of CRC.

Review article: the role of oxidative stress in pathogenesis and treatment of inflammatory bowel diseases

In this review, we focus on the role of oxidative stress in the aetiology of inflammatory bowel diseases (IBD) and colitis-associated colorectal cancer and discuss free radicals and free radical-stimulated pathways as pharmacological targets for anti-IBD drugs. We also suggest novel anti-oxidative agents, which may become effective and less-toxic alternatives in IBD and colitis-associated colorectal cancer treatment. A Medline search was performed to identify relevant bibliography using search terms including: ‘free radicals,’ ‘antioxidants,’ ‘oxidative stress,’ ‘colon cancer,’ ‘ulcerative colitis,’ ‘Crohn’s disease,’ ‘inflammatory bowel disease.’ Several therapeutics commonly used in IBD treatment, among which are immunosuppressants, corticosteroids and anti-TNF-α antibodies, could also affect the IBD progression by interfering with cellular oxidative stress and cytokine production. Experimental data shows that these drugs may effectively scavenge free radicals, increase anti-oxidative capacity of cells, influence multiple signalling pathways, e.g. MAPK and NF-kB, and inhibit pro-oxidative enzyme and cytokine concentration. However, their anti-oxidative and anti-inflammatory effectiveness still needs further investigation. A highly specific antioxidative activity may be important for the clinical treatment and relapse of IBD. In the future, a combination of currently used pharmaceutics, together with natural and synthetic anti-oxidative compounds, like lipoic acid or curcumine, could be taken into account in the design of novel anti-IBD therapies.

Pharmacokinetics and safety of single and multiple doses of Asacol tablets in Japanese healthy volunteers

INTRODUCTION

The pharmacokinetics and safety of Asacol (Tillotts Pharma AG, Ziefen, Switzerland), which has been used worldwide to treat ulcerative colitis and Crohn's disease, were studied in Japanese healthy male volunteers.

METHODS

Drug plasma concentrations and urinary and fecal excretions after a single dose (400-4800 mg) and multiple doses (3600 mg/day for 7 days) were investigated.

RESULTS

All adverse events were "not serious." The peak plasma concentration (C max) was reached at 12.3-18.0 hours after a single dose, and the C max and area under the plasma concentration-time curve (AUC) of mesalazine and its N-acetyl metabolite were proportional to the doses. The C max and AUC in non-Japanese subjects reported in the literature were closely correlated to findings in Japanese subjects, and external excretions were also similar in the Japanese and non-Japanese subjects.

CONCLUSIONS

Asacol was safe and well tolerated in this Japanese population, and the non-Japanese clinical data could be extrapolated to the Japanese population.

Comparative pharmacokinetics of equimolar doses of 5-aminosalicylate administered as oral mesalamine (Asacol) and balsalazide: a randomized, single-dose, crossover study in healthy volunteers

BACKGROUND

Existing pharmacokinetic data are insufficient to determine whether a delayed-release formulation of mesalamine (Asacol) results in greater systemic exposure to 5-aminosalicylic acid and its major metabolite N-acetyl-5-aminosalicylic acid than a prodrug (balsalazide).

AIM

To determine the pharmacokinetic parameters of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid from equimolar doses of 5-aminosalicylic acid administered as Asacol and balsalazide.

METHODS

Nineteen healthy volunteers completed an open-label, single-dose, randomized, crossover study comparing the pharmacokinetics of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid from equimolar doses of 5-aminosalicylic acid (800 mg) administered as Asacol (800 mg) and balsalazide (2250 mg). Plasma and urine samples were analysed for 5-aminosalicylic acid, N-acetyl-5-aminosalicylic acid, and balsalazide (urine only) using high-performance liquid chromatography methods with mass spectrometric detection. Pharmacokinetic parameters assessed for 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid included: percentage of dose excreted in urine (A(e)%), area under the plasma concentration-time curve (AUCt(last)); and maximum plasma concentration (C(max)).

RESULTS

The geometric mean total (5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid) urinary excretion values (A(e)%) of Asacol and balsalazide were 19.26 and 19.31% (P = 0.98). The geometric mean A(e)% values of 5-aminosalicylic acid for Asacol and balsalazide were 0.39 and 0.37% (P = 0.78); the geometric mean A(e)% values of N-acetyl-5-aminosalicylic acid for Asacol and balsalazide were 18.78 and 18.83% (P = 0.98). The geometric mean 5-aminosalicylic acid AUC(t(last)) values for Asacol and balsalazide were 3295 and 3449 ng h/mL (P = 0.85); the geometric mean N-acetyl-5-aminosalicylic acid AUC(t(last)) values for Asacol and balsalazide were 15 364 and 16 050 ng h/mL (P = 0.69). The geometric mean 5-5-aminosalicylic acid C(max) values for Asacol and balsalazide were 319 and 348 ng/mL (P = 0.80); the geometric mean N-acetyl-5-aminosalicylic acid C(max) values for Asacol and balsalazide 927 and 1009 ng/mL (P = 0.67).

CONCLUSIONS

The systemic absorption of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid from Asacol and balsalazide are comparable based upon plasma pharmacokinetic parameters and urinary excretion values.

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.

Amino acid derivatives of 5-ASA as novel prodrugs for intestinal drug delivery

In an attempt to obtain site-specific delivery of 5-ASA in the intestinal tract, we have determined the extent of absorption and metabolism of a number of novel 5-ASA derivatives, namely, (N-L-glutamyl)-amino-2-salicylic acid (1), (N-L-aspartyl)-amino-2-salicylic-acid (2), 5-aminosalicyl-L-proline-L-leucine (3), and 5-(N-L-glutamyl)-aminosalicyl-L-proline-L-leucine (4), which are selectively cleaved by intestinal brush border aminopeptidase A and carboxypeptidases. These novel prodrugs, 5-ASA, and sulfasalazine were administered to adult Fisher rats (N = 30) and to animals that had undergone prior colostomy (N = 30). Urine and feces were collected at timed intervals for 48 hr and the metabolites, 5-ASA, and N-acetyl-5-ASA were measured by high-performance liquid chromatography. The absorption and metabolism of all compounds were essentially identical in colostomized and normal animals. 5-ASA exhibited a rapid proximal intestinal absorption as evidenced by the high cumulative urinary excretion (> 65%) and low fecal excretion. Sulfasalazine, as expected, exhibited a lower urinary recovery (< 35%) and higher fecal excretion of 5-ASA and its metabolite. The novel glutamate and aspartate derivatives (1 and 2) behaved similarly to sulfasalazine, while administration of the proline-leucine derivative (3) resulted in urinary and fecal recovery values intermediate with respect to those observed with 5-ASA and sulfasalazine. 5-(N-L-Glutamyl)-aminosalicyl-L-proline-L-leucine yielded the highest fecal recovery of 5-ASA and its N-acetyl derivative, indicating a more efficient delivery to the distal bowel. Amino acid derivatives of 5-ASA appear to be potentially useful prodrugs for the site-specific delivery of 5-ASA to different regions of the intestinal tract.

Olsalazine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in inflammatory bowel disease

Olsalazine (sodium azodisalicylate; azodisal sodium) is an anti-inflammatory agent designed to deliver its active moiety, mesalazine (5-aminosalicylic acid; mesalamine), to the colon while avoiding the adverse effects associated with the use of a sulfapyridine carrier. As a prodrug, olsalazine is an effective oral treatment for both active ulcerative colitis and for maintenance of disease remission and may possibly be of benefit in patients with Crohn's colitis. Findings from both short and long term noncomparative and comparative studies demonstrate that olsalazine 1 to 3g daily in divided doses improves clinical signs and symptoms of colitis in approximately 60 to 80% of patients with acute ulcerative colitis of mild to moderate severity. This improvement rate was similar to that obtained with sulfasalazine. Lower doses of olsalazine, usually 1g daily in divided doses, also maintained remission in patients with chronic ulcerative colitis. While olsalazine effectively delivers mesalazine to the colon, the prodrug itself increases net luminal water secretion and accelerates gastrointestinal transit of a meal. The resulting diarrhoea (occurring in approximately 17% of patients and resulting in withdrawal from therapy in 6% of patients) is distinguishable from that associated with inflammatory bowel disease by the high water content and the absence of blood. Olsalazine-induced diarrhoea usually occurred soon after initiation of olsalazine therapy or dosage increase, was more frequent with higher doses and was usually transient. Dosage reduction, increases in frequency of dosing and concomitant administration with food reduced the severity in many patients with persistent olsalazine-induced diarrhoea. With the exception of diarrhoea, olsalazine was generally well tolerated. Fewer than 14% of patients allergic to or intolerant of sulfasalazine had similar reactions to olsalazine. Olsalazine appears to be a suitable therapy for the treatment of first attacks as well as acute exacerbation of mild to moderate acute ulcerative colitis, and for the maintenance of remission in patients with chronic ulcerative colitis.