Thiopurine therapy: when to start and when to stop

Relapse rate following azathioprine withdrawal in maintaining remission for Crohn's disease: a meta-analysis

BACKGROUND

The duration of use of azathioprine (Aza) and 6-mercaptopurine (6-MP) for maintaining remission for Crohn's disease is debatable.

AIM

To examine whether Aza/6-MP can be safely withdrawn in patients with Crohn's disease who have been in remission.

METHODS

The following databases were searched: MEDLINE (1950-September 2010), EMBASE (1980-September 2010), CINHAL (1981-September 2010), PubMed (1950-September 2010), and the Cochrane Central Register of Controlled Trials (CENTRAL). Randomised controlled and cohort studies comparing azathioprine continuation versus placebo or no treatment were eligible for inclusion. Primary outcomes were relapse rate after discontinuation of Aza/6-MP at 6, 12, and 18 months, and 5 and 10 years.

RESULTS

Five studies, with 256 patients and 168 controls, met the inclusion criteria. Stopping azathioprine/6-MP was found to significantly increase the risk of relapse at 6, 12, and 18 months with pooled odds ratios of 0.22 (95% CI 0.09-0.53), 0.25 (95% CI 0.11-0.56), and 0.35 (95% CI 0.21-0.6), respectively. Two trials examined relapse rate at 5 years with pooled OR 0.53 (95% CI 0.13-2.21). No trials looking at relapse rates beyond 5 years were identified.

CONCLUSIONS

There is a clear benefit of continuing Aza/6-MP for at least 18 months to maintain remission for Crohn's disease patients who established remission. There is not enough evidence to provide clear guidance on whether or not to continue Aza/6-MP treatment beyond 18 months. Well-designed randomised controlled trials addressing this issue are needed.

Thiopurine S-methyltransferase (TPMT) assessment prior to starting thiopurine drug treatment; a pharmacogenomic test whose time has come

Thiopurine S-methyltransferase (TPMT) is involved in the metabolism of thiopurine drugs. Patients that due to genetic variation lack this enzyme or have lower levels than normal, can be adversely affected if normal doses of thiopurines are prescribed. The evidence for measuring TPMT prior to starting patients on thiopurine drug therapy has been reviewed and the various approaches to establishing a service considered. Until recently clinical guidelines on the use of the TPMT varied by medical specialty. This has now changed, with clear guidance encouraging clinicians to use the TPMT test prior to starting any patient on thiopurine therapy. The TPMT test is the first pharmacogenomic test that has crossed from research to routine use. Several analytical approaches can be taken to assess TPMT status. The use of phenotyping supported with genotyping on selected samples has emerged as the analytical model that has enabled national referral services to be developed to a high level in the UK. The National Health Service now has access to cost-effective and timely TPMT assay services, with two laboratories undertaking the majority of the work at national level and with several local services developing. There appears to be adequate capacity and an appropriate internal market to ensure that TPMT assay services are commensurate with the clinical demand.

Maintenance treatment with azathioprine in ulcerative colitis: outcome and predictive factors after drug withdrawal

OBJECTIVES

Whether the duration of maintenance treatment with azathioprine (AZA) affects the outcome of ulcerative colitis (UC) is unclear. We investigated clinical outcomes and any predictive factors after withdrawal of AZA in UC.

METHODS

In this multicenter observational retrospective study, 127 Italian UC patients, who were in steroid-free remission at the time of withdrawal of AZA, were followed-up for a median of 55 months or until relapse. The frequency of clinical relapse or colectomy after AZA withdrawal was analyzed according to demographic, clinical, and endoscopic variables.

RESULTS

After drug withdrawal, a third of the patients relapsed within 12 months, half within 2 years and two-thirds within 5 years. After multivariable analysis, predictors of relapse after drug withdrawal were lack of sustained remission during AZA maintenance (hazard ratio, HR 2.350, confidence interval, CI 95% 1.434-3.852; P=0.001), extensive colitis (HR 1.793, CI 95% 1.064-3.023, P=0.028 vs. left-sided colitis; HR 2.024, CI 95% 1.103-3.717, P=0.023 vs. distal colitis), and treatment duration, with short treatments (3-6 months) more disadvantaged than >48-month treatments (HR 2.783, CI 95% 1.267-6.114, P=0.008). Concomitant aminosalicylates were the only predictors of sustained remission during AZA therapy (P=0.009). The overall colectomy rate was 10%. Predictors of colectomy were drug-related toxicity as the cause of AZA withdrawal (P=0.041), no post-AZA drug therapy (P=0.031), and treatment duration (P<0.0005).

CONCLUSIONS

Discontinuation of AZA while UC is in remission is associated with a high relapse rate. Disease extent, lack of sustained remission during AZA, and discontinuation due to toxicity could stratify relapse risk. Concomitant aminosalicylates were advantageous. Prospective randomized controlled trials are needed to confirm whether treatment duration is inversely associated with outcome.

The haemotoxicity of azathioprine in repeat dose studies in the female CD-1 mouse

Azathioprine (AZA) is a cytotoxic immunosuppressive drug used in the prevention of rejection in organ transplants and the treatment of auto-immune diseases. However, AZA is haemotoxic causing significant bone marrow depression. The present studies were to characterize the haemotoxicity of AZA in the female CD-1 mouse. In Experiment 1, a dose-ranging study, with AZA gavaged daily for 10 days, clinical evidence of toxicity was evident at 125 mg/kg and above. Experiment 2 was a dose-response study with AZA gavaged daily for 10 days at 40-120 mg/kg. At day 1 after the final dose, AZA induced a dose-related pancytopaenia, reduced femoral marrow cellularity, increases in serum levels of the cytokine fms-like tyrosine kinase 3 ligand, reduction in granulocyte-monocyte colony-forming units and erythroid colonies, and increased bone marrow apoptosis. Histology demonstrated hepatocyte hypertrophy, thymic atrophy, reduced splenic extramedullary haemopoiesis, and reduced cellularity of sternal bone marrow. In Experiment 3, AZA was dosed for 10 days at 100 mg/kg with autopsies at 1, 3, 9, 22, 29, 43 and 57 days postdosing. At 1, 3 and 9 days, haematological parameters reflected changes in Experiment 2. At 22/29 days, many blood parameters were returning towards normal; at 43/57 days, most parameters compared with controls. However, there was some evidence of a persistent (i.e. residual/late-stage) mild reduction in RBC and erythroid progenitor cell counts at day 43/57. We conclude that the CD-1 mouse provides an acceptable model for the haemotoxicity of AZA in man.

Re-introduction of azathioprine in previously intolerant patients

BACKGROUND AND AIMS

Azathioprine is an important steroid sparing agent in the management of patients with inflammatory bowel disease. However, side effects are a problem in a significant minority of patients. We proposed that desensitization might increase the number of patients able to tolerate the drug.

METHODS

Successive inflammatory bowel disease patients who were intolerant to azathioprine in our hospital gastroenterology clinic were invited to recommence the drug at a low dose, gradually building up to a therapeutic dose. Patients were observed for the recurrence of side effects. Patients who did not wish to participate were offered alternative immunosuppressant therapy.

RESULTS

Fourteen patients elected to attempt desensitization. Nine of these (64%) were able to tolerate a full dose of azathioprine. The remainder suffered a return of their side effects and were offered alternative treatment.

CONCLUSIONS

Azathioprine can be tolerated in some people who have been previously intolerant by the use of desensitization.

Medical management of Crohn's disease

Current evidence strongly suggests that Crohn's disease is caused by an abnormal response to enteric flora. This review examines the current evidence for medical management of Crohn's disease, particularly focusing on alternative therapies to corticosteroids in managing disease relapses and preventing long-term complications.