Interaction of 6-mercaptopurine and azathioprine with 5-aminosalicylic acid agents

Recent advances using immunomodulators for inflammatory bowel disease

Use of the immunomodulators thiopurines and methotrexate (MTX) in the treatment of inflammatory bowel disease (IBD), i.e., Crohn's disease and ulcerative colitis (UC), is considered to be good clinical practice. However, despite being administered to a considerable number of IBD patients over the years, questions remain about the most rational treatment regimens of azathioprine (AZA), 6-mercaptopurine (6-MP), and MTX, and results from a range of recent studies necessitate increased attention to how to optimize the use of these immunomodulators. First and foremost, it is of utmost importance to define the subgroup of IBD patients in need of immunomodulators, including those in need of combination therapy with biologic agents, especially because some side effects may be rather severe. Second, colorectal cancer is observed more often in IBD patients than in the background population. However, a recent nationwide Dutch study pointed to a preventive effect of thiopurines. Finally, the need for an appropriate approach to the discontinuation of immunomodulators is emphasized. Since controversy continues regarding the most appropriate use of immunomodulators, this paper is focusing on pharmacokinetics, pharmacogenetics, and therapeutic blood testing, as well as the occurrence of adverse events, when using AZA, 6-MP, and MTX in an attempt to determine a more up-to-date and rational treatment regimen in IBD.

Thiopurine treatment in inflammatory bowel disease: clinical pharmacology and implication of pharmacogenetically guided dosing

This review summarises clinical pharmacological aspects of thiopurines in the treatment of chronic inflammatory bowel disease (IBD). Current knowledge of pharmacogenetically guided dosing is discussed for individualisation of thiopurine therapy, particularly to avoid severe adverse effects. Both azathioprine and mercaptopurine are pro-drugs that undergo extensive metabolism. The catabolic enzyme thiopurine S-methyltransferase (TPMT) is polymorphically expressed, and currently 23 genetic variants have been described. On the basis of an excellent phenotype-genotype correlation for TPMT, genotyping has become a safe and reliable tool for determination of a patient's individual phenotype. Thiopurine-related adverse drug reactions are frequent, ranging from 5% up to 40%, in both a dose-dependent and -independent manner. IBD patients with low TPMT activity are at high risk of developing severe haematotoxicity if pharmacogenetically guided dosing is not performed. Based on several cost-benefit analyses, assessment of TPMT activity is recommended prior to thiopurine therapy in patients with IBD. The underlying mechanisms of azathioprine/mercaptopurine-related hepatotoxicity, pancreatitis and azathioprine intolerance are still unknown. Although the therapeutic response appears to be related to 6-thioguanine nucleotide (6-TGN) concentrations above a threshold of 230-260 pmol per 8 x 10(8) red blood cells, at present therapeutic drug monitoring of 6-TGN can be recommended only to estimate patients' compliance.Drug-drug interactions between azathioprine/mercaptopurine and aminosalicylates, diuretics, NSAIDs, warfarin and infliximab are discussed. The concomitant use of allopurinol without dosage adjustment of azathioprine/mercaptopurine leads to clinically relevant severe haematotoxicity due to elevated thiopurine levels. Several studies indicate that thiopurine therapy in IBD during pregnancy is safe. Thus, azathioprine/mercaptopurine should not be withdrawn in strictly indicated cases of pregnant IBD patients. However, breastfeeding is contraindicated during azathioprine/mercaptopurine therapy. Use of azathioprine/mercaptopurine for induction and maintenance of remission in corticosteroid-dependent or corticosteroid-refractory IBD, particularly Crohn's disease, is evidence based. To improve response rates in thiopurine therapy of IBD, comprehensive analyses including metabolic patterns and genome-wide profiling in patients with azathioprine/mercaptopurine treatment are required to identify novel candidate genes.

Debate: should mesalamine be used in Crohn's disease?: comments and conclusions

Mesalamine has a well-established role in the management of ulcerative colitis. However, its role in the management of Crohn's disease (CD) is less clear. Studies evaluating its therapeutic value in CD have produced both positive and negative results. Meta-analyses have not clarified the situation, possibly because they have combined studies of different design. This debate critically examines the evidence for and against the use of mesalamine in CD.

A prospective randomized observer-blind 2-year trial of azathioprine monotherapy versus azathioprine and olsalazine for the maintenance of remission of steroid-dependent ulcerative colitis

OBJECTIVE

The aim of this prospective study was to assess whether the coadministration of azathioprine (AZA) and olsalazine is superior to AZA monotherapy in maintaining remission of steroid-dependent ulcerative colitis (UC).

METHODS

Patients with steroid-dependent UC in remission were randomized to receive AZA alone (2.2 mg/kg) or in combination with olsalazine (0.5 g tid). Remission was defined as steroid withdrawal, an Ulcerative Colitis Clinical Activity Index (UCCAI) score of <2, an Ulcerative Colitis Disease Activity Index (UCDAI) score of 0, and a negative colonoscopy and histology. Patients were followed in the outpatient clinic every month for 2 yr. The study protocol included 1) monthly clinical examination, assessment of UCCAI, hematological and biochemical tests, and compliance with treatment; 2) a sigmoidoscopy and completion of inflammatory bowel disease quality-of-life questionnaire (IBD-Q) and UCDAI every 3 months; and 3) total colonoscopy with biopsies at the end of the first and second year of the trial.

RESULTS

Seventy patients were randomized to receive AZA alone (n = 34) or with olsalazine (n = 36). Three patients in each group developed side effects or could not comply with treatment and were withdrawn from the study. Three patients receiving AZA relapsed after the first year of the study and three after the second year of the study (19%). In the combination therapy group four patients relapsed after the first year of study and two after the second year of the study (18%). Relapse rates were not significant whether analyzed by intention-to-treat or per protocol. There were no significant differences between groups in time to relapse or discontinuation of treatment, UCCAI, UCDAI, or IBD-Q scores. However, the number of adverse events and the cost of treatment were significantly higher, whereas compliance with treatment was poorer in the combination therapy.

CONCLUSION

Patients with steroid-dependent UC successfully maintained in remission on AZA are not in need of 5-aminosalicylic acid compounds.

Rectocolite ulcéro-hémorragique chronique active

OBJECTIVE

To know whether the therapeutic protocol applied in the case of severe acute ulcerative colitis (UC) associating ciclosporine and azathioprine was also effective in the case of moderate chronic active ulcerative colitis (UC).

SUBJECTS AND METHODS

in this retrospective study 10 patients (31-65 years, 6 distal colitis, 1 left colitis, 3 pancolitis) moderately active and corticosteroid-resistant or dependent were included. Patients received ciclosporine intraveinously (4 mg/kg/d) and were evaluated 10 days later. If efficient, ciclosporine was given orally for 3 Months, azathioprine was introduced and steroids were progressively tapered.

RESULTS

on inclusion the clinical score, based on the Mayo Clinic score, was of 5.7 +/- 0.5. On Day 10, the score decreased significantly (2.1 +/- 0.7, p<0.001) and the therapeutic effect was sustained at the third Month (1.8 +/- 0.7). With azathioprine, 4 patients were still in remission with a mean follow up of 23.3 +/- 15.5 Months.

CONCLUSION

therapeutic scheme proposed in severe acute UC failing to respond to steroids may be helpful in some patients with a chronic active UC. Clinical improvement is rapid and long-term response is maintained in about 1 patient out of 2.

Review article: the treatment of inflammatory bowel disease with 6-mercaptopurine or azathioprine

The thioguanine derivative, azathioprine, is a prodrug of 6-mercaptopurine that is further metabolized by various enzymes present in the liver and gut. Azathioprine and 6-mercaptopurine have been used in the treatment of inflammatory bowel disease, i.e. ulcerative colitis and Crohn's disease, for more than 30 years. However, widespread use of azathioprine or 6-mercaptopurine in inflammatory bowel disease is of more recent origin, the primary reason being a long-standing debate on the efficacy of these agents in inflammatory bowel disease. Both drugs are slow acting, which is why clinical efficacy cannot be expected until several weeks or even months of treatment have elapsed. Consequently, azathioprine and 6-mercaptopurine have no place as monotherapy in the treatment of acute relapsing inflammatory bowel disease. Today, azathioprine and 6-mercaptopurine are the most commonly used immunomodulatory drugs in the treatment of inflammatory bowel disease. Their clinical effects are probably identical, although their exact mode of action is still unknown. The mode of action of azathioprine is thought to be multifactorial, including conversion to 6-mercaptopurine (which acts as a purine antimetabolite), possible blockade of thiol groups by alkylation, inhibition of several pathways in nucleic acid biosynthesis (preventing proliferation of cells involved in the determination and amplification of the immune response) and damage to DNA through the incorporation of thiopurine analogues. However, 6-thioguanine nucleotides may accumulate in toxic doses in myeloid precursor cells, resulting in life-threatening myelosuppression. Azathioprine and 6-mercaptopurine are further known to alter lymphocyte function, reduce the number of lamina propria plasma cells and affect natural killer cell function. The purpose of this comprehensive review is to suggest guidelines for the application of azathioprine and 6-mercaptopurine in the treatment of inflammatory bowel disease.

Safety and efficacy of azathioprine in the maintenance of ciclosporin-induced remission of ulcerative colitis

BACKGROUND

It has been shown that azathioprine prolongs the response to ciclosporin of steroid-refractory ulcerative colitis, but no specific data are available concerning its toxicity in this indication.

AIM AND METHODS

The charts of 21 patients with steroid-refractory ulcerative colitis who received azathioprine overlapping with a successful ciclosporin course were reviewed for the onset of toxicity. The controls consisted of 48 initial responders to steroids who received azathioprine for steroid-dependence or resistance/toxicity.

RESULTS

Two of the 21 patients were withdrawn because of hypersensitivity to azathioprine. The remaining 19 were treated for a median of 18 months together with a median daily steroid dose of 35 mg (10-75 mg) to be tapered off. Toxicity (31%) included leukopenia alone (two cases), cholestasis alone (one case), cholestasis and increased amylase (one case), increased amylase alone (one case), and cutaneous infection (one case). The frequency of withdrawal was 21%. The mean daily steroid doses were reduced from 38 mg to 3.8 mg in the study cohort, and from 25 mg to 8 mg in the controls, among whom toxicity (27%) included four cases each of leukopenia and increased amylase, two cases each of alteration of liver enzymes and infection, and one case of gastric intolerance. Ten of the 48 controls (20%) were withdrawn from the study.

CONCLUSION

Azathioprine is as effective and safe in the maintenance of the response of patients with steroid-refractory ulcerative colitis to ciclosporin as it is in the treatment of those who respond to steroids.