Toxicity of azathioprine: why and when? analysis of the prevalence of polymorphism in Joinville, SC, Brazil

Myasthenia gravis and azathioprine treatment: Adverse events related to thiopurine S-methyl-transferase (TPMT) polymorphisms

Azathioprine (AZA) is the most common immunosuppressive drug used to treat myasthenia gravis (MG). To analyses the prevalence of thiopurine S-methyl-transferase (TPMT) genotypes and their association with adverse events due to azathioprine therapy in MG patients. Allele-specific polymerase chain reaction (PCR) and PCR with restriction fragment length polymorphism (RFLP) analysis were carried out to determine the prevalence of the most common TPMT genotypes (*2, *3A, *3B and *3C) in 50 MG patients from Southern Brazilian. The frequency of adverse reactions due to azathioprine therapy was analysed and correlated with different genotypes groups. The prevalence of TPMT gene variants was 12%. The allelic frequency of variant TPMT*2 (C238G), TPMT*3A (G460A/A719G), TPMT*3B (G460A), and TPMT*3C (A719G) genotypes was 1, 3, 2 and 1%, respectively. Adverse events occurred in 44%, of MG patients, of which 86% were minor and 14% were major. One patient, who presented a major adverse event (bone marrow suppression), was homozygous for the TPMT*3A genotype. Our study estimated the prevalence of TPMT genotypes for Brazilian MG patients. The profile of TPMT genotypes was different from other Brazilian populations. Hardy-Weinberg equilibrium and allelic frequencies of TPMT*3A and TPMT*3B, respectively, were different than expected, a finding that suggests a possible founder effect. Major adverse events were statistically significant for TPMT genotypes compared to wild-type. Although TPMT genotype has been associated with AZA-related adverse events, since no statistically significant difference among wild-type and other TPMT genotypes for minor adverse events, our study supports the view that TPMT genotype alone is not enough to adequately personalise the AZA therapy in MG patients. In conclusion, these results were important to characterise the prevalence of TPMT gene variants in MG patients treated with AZA and correlate the adverse events of this therapy in a real-world outpatient clinic from Southern Brazil.

Severe cholestasis due to azathioprine in Behcet's disease

Azathioprine (AZA) is an immunosuppressive drug that is widely used in the treatment of autoimmune diseases. Although AZA is used widely, many studies reported that AZA-related hepatotoxicity is rather rare. We aimed to present a case with severe cholestatic hepatitis due to AZA use for Behcet's disease. Three weeks after starting AZA for the treatment of uveitis, the patient was admitted to our clinic with cholestasis and constitutional symptoms. In liver biopsy, findings were in accordance with drug reaction, and the AZA treatment was stopped. After 2 months, bilirubin levels and liver tests results became normal. As a result, given that AZA may cause severe cholestasis, the drug should be stopped if idiosyncrasy or hypersensitivity develops. If there is a debate in the diagnosis, histopathological evaluation of the liver would be the major issue because of the correct diagnosis of the drug toxicity and excluding other aetiologies.

Pharmacogenomics research and clinical implementation in Brazil

We searched PubMed entries and the Lattes database of Brazilian Pharmacogenetics Network investigators, for pharmacogenetic/genomic (PGx) studies in the Brazilian population, focusing on the drugs and genes included in the Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines. Warfarin was the most extensively studied drug in a PGx context: a genomewide association study targeting warfarin stable dose identified significant signals in VKORC1 and CYP2C9, several PGx dosing algorithms were developed based on these and other genes, and the implications of population admixture on extrapolation of dosing recommendations in the CPIC guidelines were examined. A study in renal transplanted patients disclosed association of CYP3A5*6 and CYP3A5*7 with tacrolimus dosing, which led to addition of these variants to CYP3A5*3 in the CPIC tacrolimus guideline. Studies verified predisposition of HIV-positive carriers of UGT1A1*28 to severe atazanavir-induced hyperbilirubinaemia, intolerance to 5-fluorouracyl in gastrointestinal cancer patients with deleterious DPYD variants, failure of HCV-infected carriers of IFNL3 rs12979860 to obtain a sustained viral response to PEG-IFN-α, and hypersensitivity reactions to abacavir in HIV-positive carriers of HLA-B*57:01. No prospective analyses of drug therapy outcomes or cost-effectiveness assessments of PGx-guided therapy were found. In conclusion, the limited adoption of PGx-informed drug prescription in Brazil reflects combination of recognized barriers to PGx implementation worldwide plus factors specific to the Brazilian population. The latter include rarity/absence of genetic variants on which international PGx guidelines are based (eg HLA-B*15.02 for phenytoin and carbamazepine) and the caveat of extrapolating to the admixed Brazilian population, guidelines based on categorical variables, such as continental ancestry (eg warfarin guidelines), "race" or ethnicity.

Forensic pharmacovigilance: Newer dimension of pharmacovigilance

Drug safety for the patients is of paramount importance for a medical professional. Pharmacovigilance attempts to ensure the safety of patients by keeping a close vigil on the pattern of adverse events secondary to drug use. Number of medicolegal cases is at rise since last few years. Forensic sciences and pharmacovigilance need to work hand in hand to unlock the mystery of many criminal and civil proceedings. Pharmacovigilance offers its wide scope in forensic sciences by putting forward its expertise on adverse profile of drugs which may be instrumental in solving the cases and bringing the justice forth. It may range from as simple affairs as defining the adverse drug reaction on one hand to putting expert advice in critical criminal cases on the other one. Pharmacovigilance experts have to abide by the ethics of the practice while executing their duties as expert else it may tarnish the justice and loosen its dependability. As a budding discipline of science, it is confronted with several hurdles and challenges which include reluctance of medical professionals for being involved in court proceedings, extrapolations of facts and data and variations in law across the globe etc. These challenges and hurdles call the medical fraternity come forward to work towards the momentous application of pharmacovigilance in the forensic sciences. Evidence based practice e.g. testing the biological samples for the presence of drugs may prove to be pivotal in the success of this collaboration of sciences.

Suspected azathioprine induced liver cirrhosis: an unusual side effect

In recent years, the hepatotoxic potential of thiopurines, in particular 6-thioguanine (6-TG) has been discussed in literature. However, cirrhosis was exceptionally reported. We report the case of a 56-year-old woman with ileocaecal Crohn's disease treated with azathioprine. After taking azathioprine (2 mg/kg daily) for four years, she underwent surgical treatment for acute intestinal obstruction. In peroperative, we noticed a cirrhotic liver. A surgical biopsy was performed and the diagnosis of cirrhosis was confirmed. Autoimmune and viral liver diseases were ruled out by laboratory parameters. Therefore, Azathioprine is believed to be the causative actor for inducing liver cirrhosis. Thus, treating inflammatory bowel disease effectively while trying to limit iatrogenic disease is a continuous struggle.

Royal jelly attenuates azathioprine induced toxicity in rats

In the present study, we investigated the potential protective effects of royal jelly against azathioprine-induced toxicity in rat. Intraperitoneal administration of azathioprine (50 mg/kgB.W.) induced a significant decrease in RBCs count, Hb concentration, PCV%, WBCs count, differential count and platelet count, hepatic antioxidant enzymes (reduced glutathione and glutathione s-transferase) and increase of serum transaminases (alanine aminotransferase and aspartate aminotransferase enzymes) activities, alkaline phosphatase and malondialdehyde formation. Azathioprine induced hepatotoxicity was reflected by marked pathological changes in the liver. Oral administration of royal jelly (200 mg/kgB.W.) was efficient in counteracting azathioprine toxicity whereas it altered the anemic condition, leucopenia and thrombocytopenia induced by azathioprine. Furthermore, royal jelly exerted significant protection against liver damage induced by azathioprine through reduction of the elevated activities of serum hepatic enzymes. Moreover, royal jelly blocked azathioprine-induced lipid peroxidation through decreasing the malondialdehyde formation. In conclusion, royal jelly possesses a capability to attenuate azathioprine-induced toxicity.