[Thiopurine methyltransferase activity and myelosuppression in inflammatory bowel disease patients treated with azathioprine and 6-mercaptopurine]

Undiagnosed thyroid dysfunction, thyroid antibodies, and iodine excretion in a Mediterranean population

The prevalence of thyroid dysfunction varies in different populations. The aim of this cross-sectional study was to analyze the prevalence of undiagnosed thyroid dysfunction and thyroid antibodies and their relationship with urine iodine excretion in a representative sample of 1,124 (55.5% women; mean age: 44.8 ± 15.2 years) non-hospitalized Mediterranean adults, in Catalonia (Spain). Free thyroxine, thyroid-stimulating hormone, thyroperoxidase and thyroglobulin antibodies, and urine iodine were measured. Undiagnosed thyroid dysfunction was 5.3% (hypothyroidism 3.8%; 56.66% of these subjects were women). The total (diagnosed + undiagnosed) thyroid dysfunction was 8.9% (71.15% women). Thyroperoxidase antibodies were positive in 2.4% of men and 9.4% of women and thyroglobulin antibodies, in 1.3% of men and 3.8% of women. No differences were observed in urine iodine between groups with thyroid dysfunction and euthyroidism, or between subjects with positive or negative antibodies. In subjects over 60, undiagnosed thyroid dysfunction was 9.8% (hypothyroidism 6.9%, hyperthyroidism 3.3%; 36.36% women) and total thyroid dysfunction 13.61% (53.12% women). Women and men over 60 had similar thyroid dysfunction prevalence. Thus, aggressive case-finding should be recommended in both, over 60.

Thiopurine-induced myelotoxicity in patients with inflammatory bowel disease: a review

AIM

Probably, the most important and potentially lethal adverse event of azathioprine (AZA) and mercaptopurine (MP) is myelosuppression. Our aim was to conduct a review of AZA/MP-induced myelotoxicity in inflammatory bowel disease (IBD) patients.

METHODS

Bibliographical searches were performed in MEDLINE/EMBASE. The studies evaluating thiopurine-induced myelotoxicity in patients with IBD were reviewed. The cumulative incidence and the incidence rate of AZA/MP-induced myelotoxicity were calculated by a meta-analysis.

RESULTS

In total, 66 studies (8,302 patients) were included. The cumulative incidence of AZA/MP-induced myelotoxicity was 7% (95% confidence interval [CI] 6-8%). The incidence rate (per patient and year of treatment) of the drug-induced myelotoxicity was 3% (95% CI 3-4%). The risk was roughly similar with AZA and with MP (7%vs 9%). The duration of AZA/MP treatment in patients with myelotoxicity ranged from 12 days to 27 yr. The cumulative incidence of infections among AZA/MP-induced myelotoxicity patients was 6.5%. The cumulative incidence of severe myelotoxicity was 1.1% (incidence rate 0.9%). Three deaths were reported due to myelotoxicity (cumulative incidence 0.06%, 95% CI 0.02-0.17%). The risk of death among patients who developed myelotoxicity was 0.94% (95% CI 0.32-2.70%).

CONCLUSION

The incidence rate of myelotoxicity in IBD patients receiving AZA/MP is approximately 3% per patient and year of treatment. Although bone marrow toxicity may develop at any time after starting the therapy, this happens more frequently during the first months. The incidence rate of severe myelotoxicity is less than 1% per patient and year of treatment, and the mortality risk is less than 0.1% (which means that the risk of death among IBD patients who develop myelotoxicity is approximately 1%).

[Monitoring of thiopurine methyltransferase and thiopurine metabolites to optimize azathioprine therapy in inflammatory bowel disease]

Determination of the activity of thiopurine methyltransferase (TPMT) and of thiopurine metabolites (6-thioguanine and 6-methylmercaptopurine nucleotides) could be useful for individualized monitoring of azathioprine (AZA) and 6-mercaptopurine (6-MP) doses. TPMT activity in the general population follows a trimodal distribution, in which approximately 0.3% of the population is homozygotic for the low-activity allele. A notable correlation has been observed between the low TPMP activity genotype or phenotype and the risk of myelotoxicity. Patients with a high TPMT activity genotype or homozygous phenotype should receive immunosuppressive doses that have clearly been demonstrated to be effective. In contrast, in patients with a low TPMT activity genotype or homozygous phenotype, the use of AZA/6-MP should be contraindicated or only very small doses should be administered. Importantly, TPMP deficiency explains only some cases of myelotoxicity and consequently periodic laboratory testing should be performed in patients receiving AZA/6-MP, even though TPMP function may be normal. Currently, the utility of routine thiopurine metabolite determinations in patients undergoing AZA/6-MP therapy has not been established and this practice should be limited to specific situations such as lack of response to thiopurine therapy or the occurrence of thiopurine-related adverse effects. Randomized trials comparing the routine strategy of AZA/6-MP dosing (based exclusively on the patient's weight) versus individualized monitoring (based on quantification of TPMP activity and/or thiopurine metabolites) are required before definitive conclusions on the most effective alternative can be drawn.

Efficacy and safety of thiopurinic immunomodulators (azathioprine and mercaptopurine) in steroid-dependent ulcerative colitis

BACKGROUND

The efficacy of azathioprine in the management of steroid-dependent ulcerative colitis is taken for granted. However, study populations frequently include together steroid-dependent and refractory patients.

AIM

To assess the efficacy and safety of thiopurinic immunomodulators in strictly defined steroid-dependent ulcerative colitis.

METHODS

Survey of 34 patients with steroid-dependent ulcerative colitis, treated with azathioprine according to protocol. Therapeutical success: glucocorticoid withdrawal within 12 months, without steroid requirements during another year.

RESULTS

Mean age was 39.1 +/- 17 years. Pancolitis and extensive colitis accounted for 50% of cases. Therapeutic success of immunomodulator treatment reached 70.6%, intention to treat analysis (confidence interval 95%: 52-84%) and 72.7%, as per protocol (confidence interval 95%: 54-86%). Mean time to steroid withdrawal was 4.6 months. In therapy successes, mean corpuscular volume and total serum bilirubin increased with treatment time (P = 0.0001). Fifteen adverse effects were observed in 13 patients (38%). Azathioprine was withdrawn in seven cases (20.6%); in four of them (with liver toxicity), treatment with mercaptopurine was indicated.

CONCLUSIONS

Therapy with thiopurinic immunomodulators (azathioprine) represents the first option in the management of steroid-dependent ulcerative colitis. Its efficacy (70%) and its acceptable safety support this view. Increasing mean corpuscular volume and serum bilirubin values may be a surrogate marker of a beneficial effect.

Actividad de la tiopurina metiltransferasa en pacientes con hepatitis autoinmune

BACKGROUND AND OBJECTIVE

The measurement of the activity of thiopurine methyltransferase (TPMT) is useful to monitor, on an individual basis, the dose of azathioprine in order to identify patients at risk of myelotoxicity. However, the distribution of the enzymatic activity in patients with autoimmune hepatitis is unknown. Our objective was to analyze the activity of TPMT in a group of 200 patients with autoimmune hepatitis and to evaluate the possible effect of some variables such as the treatment with azathioprine on this activity.

PATIENTS AND METHOD

The activity of TPMT was determined by a radiochemical method; the activity was determined in the erythrocytes of patients with autoimmune hepatitis from 31 Spanish hospitals. We studied the relationship between TPMT levels and several demographic variables as well as its correlation with azathioprine treatment.

RESULTS

We included 209 patients (80% females, mean age 50 years, 39% on azathioprine). The mean value of TPMT was 20.7 U/ml erythrocytes (from 0 to 39). TPMT levels were adjusted to a normal distribution. 1%, 9% and 90% patients had low (< 5 U/ml), intermediate (5-13.7 U/ml) and high (>= 13.8 U/ml) TPMT levels, respectively. In the multivariate analysis, there were no differences when comparing the mean TPMT values according to age, gender or previous azathioprine treatment.

CONCLUSIONS

TPMT activity in patients with autoimmune hepatitis displays a similar distribution to that reported in other populations (approximately 1% of patients have low levels and 9% have intermediate levels) and it does not depend on the age, gender or simultaneous azathioprine treatment.