Azathioprine

Advances in Thiopurine Drug Delivery: The Current State-of-the-Art

Thiopurines (mercaptopurine, azathioprine and thioguanine) are well-established maintenance treatments for a wide range of diseases such as leukemia, inflammatory bowel disease (IBD), systemic lupus erythematosus (SLE) and other inflammatory and autoimmune diseases in general. Worldwide, millions of patients are treated with thiopurines. The use of thiopurines has been limited because of off-target effects such as myelotoxicity and hepatotoxicity. Therefore, seeking methods to enhance target-based thiopurine-based treatment is relevant, combined with pharmacogenetic testing. Controlled-release formulations for thiopurines have been clinically tested and have shown promising outcomes in inflammatory bowel disease. Latest developments in nano-formulations for thiopurines have shown encouraging pre-clinical results, but further research and development are needed. This review provides an overview of novel drug delivery strategies for thiopurines, reviewing modified release formulations and with a focus on nano-based formulations.

Efficacy and Safety of Switching to Azathioprine for Mycophenolate-Induced Diarrhea in Renal Transplant Recipients

BACKGROUND

Diarrhea is a common adverse effect of mycophenolate treatment in renal transplant recipients. In patients with mycophenolate-induced diarrhea, one option is to switch to mycophenolate to azathioprine. In this study, we aimed to define the safety and efficacy of switching from mycophenolate to azathioprine for mycophenolate-related diarrhea in renal transplant recipients.

METHODS

A total of 177 patients, 59 of whom were switched to azathioprine because of diarrhea and 118 of whom comprised a matched control group without diarrhea and continued mycophenolate treatment participated in this study. We analyzed the effect of switching to azathioprine from mycophenolate on amelioration of diarrhea and graft survival.

RESULTS

We observed that 89.8% of patients who switched to azathioprine because of diarrhea had improved diarrhea complaints. Patients switched to azathioprine because of diarrhea had lower glomerular filtration rates (P < .001) and higher proteinuria (P < .001) compared with the control group before the switch. Patients switched to azathioprine compared with a subgroup of 59 control patients were matched to patients switched to azathioprine in terms of baseline renal function and proteinuria in addition to demographic parameters had higher 10-year graft loss compared with patients who continued mycophenolate (P = .03). Particularly in patients with a glomerular filtration rate <30 mL/min at the time of conversion, the risk of early graft loss was high.

CONCLUSIONS

Although switching from mycophenolate to azathioprine was an effective approach to improve diarrhea, this approach is associated with increased risk of graft loss.

The long-term risk of continuous immunosuppression using thioguanides in inflammatory bowel disease

The efficacy of thiopurine treatment in the induction, and especially maintenance, of remission in inflammatory bowel disease is well proven; however, it is associated with side effects in both medium and long-term use. The potential harmful effects may be anticipated and minimised by due diligence prior to commencing these drugs followed by close monitoring of haematological and biochemical parameters once started. Careful clinical examination and history taking are also essential. Affected patients are expected to lead lives that include travel, employment and pregnancy - the implications of continued thiopurine therapy in such patients are discussed.

Drug monitoring in systemic lupus erythematosus: a systematic review

OBJECTIVES

To conduct an evidence-based review of the common medication toxicities and strategies and utility of drug toxicity monitoring among patients with systemic lupus erythematosus (SLE).

METHODS

PubMed and other databases were searched for articles published between the years 1960 and 2010 for keywords referring to medication toxicity or monitoring strategies for 7 drugs commonly used in SLE. All relevant English-language articles were reviewed. Most of the evidence we reviewed comprised studies that addressed the incidence of toxicity-randomized trials that compare different monitoring strategies for these drugs do not exist.

RESULTS

Data to describe the frequency of adverse events and appropriate strategies for screening for these events are scarce. Toxicities do not appear to be substantially more common among patients with SLE compared to other conditions for which these drugs are used.

CONCLUSIONS

Our review demonstrates that the scientific basis for many aspects of drug toxicity monitoring is weak and that most current recommendations are based largely on expert consensus. We present a future research agenda to address these gaps.

Treatment of lupus nephritis

Renal involvement in systemic lupus erythematosus (SLE) is a serious complication of the disease. However, the prognosis of patients with lupus nephritis is continually improving with 10-year survival rates now greater than 75%. This improvement reflects earlier diagnosis due to more sensitive and specific diagnostic tests, better clinical appreciation of the natural history, and improved treatment of SLE and its manifestations. This review of the treatment of lupus nephritis has graded the level of evidence of specific treatment using the guidelines of the US Preventive Service Task Force. Although many new treatments have been advocated, the best evidence for treating proliferative lupus nephritis relies on a strategy combining specific treatment of the SLE as well as generalised treatment of the associated comorbidities. This strategy involves a combination of corticosteroids and cytotoxic agents plus or minus the adjunctive use of antimalarials, coordinated aggressive management of hypertension, proteinuria, infections, dyslipidaemia, thrombotic coagulopathy and potential renal replacement therapies.

Old and new drugs used in rheumatoid arthritis: a historical perspective. Part 1: the older drugs

Rheumatoid arthritis is the paradigmatic immune-mediated inflammatory arthropathy and may be of comparatively recent, New World origin. Apart from the symptom-relieving nonsteroidal anti-inflammatory drugs, whose natural congeners have been in use since antiquity for musculoskeletal pain and inflammation, only a dozen drugs or drug classes--the disease-modifying antirheumatic drugs--are currently in common use in rheumatoid arthritis. Development of these drugs has been a notable achievement of the 20th century. Some were developed serendipitously (glucocorticoids, antimalarials), some were the product of faulty reasoning (gold, D-penicillamine), and others were applied for plausible reasons but whose mechanism remains unproven (sulfasalazine, methotrexate, minocycline). A minority were originally applied on the basis of actions that remain germane to the pathophysiology of rheumatoid arthritis as currently understood (azathioprine, cyclosporine, leflunomide, infliximab, etanercept). Among the latter are the more recently introduced and effective agents. The practical use of these drugs is determined by efficacy-toxicity considerations, which have also driven the recent development of the cyclooxygenase-2-selective nonsteroidal anti-inflammatory drugs.

Reduced thiopurine methyltransferase activity and development of side effects of azathioprine treatment in patients with rheumatoid arthritis

OBJECTIVE

To investigate thiopurine enzyme activities for their possible value in predicting the development of azathioprine (AZA)-related toxicity in patients with rheumatoid arthritis (RA).

METHODS

Patients with longstanding RA (n = 33) were enrolled in a study of treatment with AZA. Before the initiation of AZA treatment and at months 1 and 6 of treatment, we measured activities of the purine key enzymes hypoxanthine guanine phosphoribosyltransferase, 5'-nucleotidase, purine nucleoside phosphorylase, and thiopurine methyltransferase (TPMT). Controls included patients with early RA (n = 24) and healthy volunteers (n = 42).

RESULTS

Fourteen of the 33 patients rapidly developed severe side effects, most frequently gastrointestinal (GI) intolerance. Compared with the other groups, the group with adverse effects had significantly lower TPMT activities (P = 0.004). Seven of 8 patients with reduced ("intermediate") baseline TPMT levels developed toxicity, resulting in a significant relationship (P = 0.005) between toxicity and "intermediate" TPMT activity. Compared with "high" activity, baseline intermediate TPMT activity gave a relative risk of 3.1 (95% confidence interval 1.6-6.2) for the development of severe toxicity with AZA treatment.

CONCLUSION

In RA patients, inherited intermediate TPMT activity seems predictive for the development of severe side effects of AZA. Clinicians should consider measuring TPMT prior to treatment initiation to improve the safety of AZA use. We hypothesize that GI intolerance may also be related to a thiopurine metabolic imbalance.

Therapeutic approaches to the treatment of rheumatoid disease

Successful treatment of patients with rheumatoid arthritis demands an understanding of the rationale, clinical use, and side effects of the various antirheumatic modalities. Most patients can be treated effectively with salicylates or other nonsteroidal anti-inflammatory drugs, although some with more serious disease require the addition of a slow-acting agent such as gold, d-penicillamine, or methotrexate.