Effect of gervital in attenuating hepatotoxicity caused by methotrexate or azathioprine in adult albino rats.

Methotrexate (MTX) and azathioprine (AZA) are chemotherapeutic, antimetabolic, and immunosuppressive agents with substantial risks such as oxidative lesions to the liver. This study examined the effect of grape seed extract (GSE; gervital) in attenuating hepatotoxicity caused by MTX or AZA treatment. Rats were divided into six groups (six rats per group): Group I, normal control group; Group II, GSE (150 mg/kg/day); Group III, MTX (8 mg/kg/week); Group IV, AZA (15 mg/kg/day); Group V, GSE (150 mg/kg/day) + MTX (8 mg/kg/week); and Group VI, GSE (150 mg/kg/day) + AZA (15 mg/kg/day). After 35-day experimental period, all rats were sacrificed and blood was collected for biochemical study and hemoglobin (Hb) assessment. The liver was weighed and triaged for histological, ultrastructural, and biochemical studies. MTX and AZA treatment decreased Hb levels, increased relative liver weight, increased the activity of glutamate pyruvate transaminase (ALT) and glutamate oxaloacetate transaminase (AST) aminotransferase (ALT) and aspartate aminotransferase (AST) values, and displayed histopathological and ultrastructural alterations. These changes included the disorganization of hepatocytes, pyknosis, karyolysis of some nuclei, and mononuclear leukocytic infiltration. The liver with significant oxidative stress (OS) showed decreased reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) and increased malondialdehyde (MDA) levels. In contrast, GSE administration ameliorated ALT, AST, and all histopathological and ultrastructural changes. GSE treatment also reduced MDA levels but increased the antioxidant parameters. In conclusion, it was concluded that GSE supplementation could be considered as a promising antioxidant in reducing OS, histopathological and ultrastructural alterations induced by MTX and AZA.

In vitro study of the toxic and teratogenic effects of prednisolone, azathioprine and mycophenolate mofetile on embryological development of rats.

This study aimed to evaluate the effects of the glucocorticoid prednisolone, the mycophenolic acid prodrug, azathioprine, and the fungi fermentation end product, mycophenolate mofetile on the embryological development of rats. Nine day-old rat embryos were cultured in rat serum containing prednisolone at varying concentrations (5-30 µg/ml) for 48 h. The test groups were cultured separately in rat serum containing 0.3-10 µg/ml azathioprine and 1-10 µg/ml mycophenolate mofetile. Embryonic development parameter effects of both drugs in combination with prednisolone (20 µg/ml) were studied using morphological methods, with special attention given to the incidence of malformations. The genotoxic effects of agents evaluated with the TUNEL test revealed that prednisolone is not a cause of developmental toxicity. The maximum safe dose of prednisolone that could be used in combination with other immunosuppressive agents was determined to be 20 µg/ml. Azathioprine was found to be toxic and teratogenic for the rat embryos beginning at a dose of 1 µg/ml. Dose-dependent toxic and teratogenic effects of mycophenolate mofetile were detected at doses lower than normal clinical ones.

Recombinogenic, genotoxic, and cytotoxic effects of azathioprine using in vivo assays.

Azathioprine (Aza) is a purine antimetabolite immunosuppressant that is widely employed for immunosuppressive therapy in post-transplant recipients or patients with autoimmune diseases. Chronic use of immunosuppressants might produce several side effects, including a high rate of neoplasms in these patients. Considering that genotoxic effects are associated with an increased risk of developing cancer, the aim of this study was to examine the recombinogenic, genotoxic, and cytotoxic effects of Aza using Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster, as well as comet and micronucleus assays in mouse bone marrow cells. Further, the adverse effects of Aza were determined in mouse hepatic and renal tissues using histopathological analysis. Data demonstrated that Aza induced significant increased genotoxicity in D. melanogaster and mouse bone marrow cells at all concentrations tested. Homologous recombination was the predominant genotoxic event noted for the first time to be initiated by Aza in SMART. In histopathological analysis, Aza did not show any marked toxic activity in mouse hepatic and renal tissues. Therefore, the high rate of neoplasms reported in patients with long-term use of Aza may be attributed, at least partially, to the genotoxic action of this drug.

Hepatotoxicidade induzida por azatioprina em portadora da síndrome de Vogt-Koyanagi-Harada / Azathioprine-induced hepatotoxicity in a Vogt-Koyanagi-Harada syndrome patient

Este relato teve como objetivo apresentar um caso de hepatotoxicidade colestática induzida por azatioprina em portadora da síndrome de Vogt-Koyanagi-Harada. À admissão, apresentava icterícia +3/+4, acolia fecal e colúria, além de aumento de marcadores hepáticos, sendo compatível com síndrome colestática, cuja etiologia foi confirmada após exclusão de outras causas possíveis e retirada da azatioprina. A paciente evoluiu, após 1 semana de retirada do fármaco, com diurese livre de coloração menos escura e evacuação presente, sem acolia. Além disso, houve melhora nos exames que precederam a alta hospitalar

This report aimed at presenting a case of azathioprine-induced cholestatic hepatotoxicity in a patient with Vogt-Koyanagi-Harada syndrome. On admission, she presented with jaundice +3/+4, acholic feces, and choluria, as well as increased hepatic markers, all consistent with cholestatic syndrome, the etiology of which was confirmed after other possible causes were ruled out and azathioprine was discontinued. After 1 week of the drug discontinuation, the patient progressed with free diuresis of lighter color and defecation, with no acholia. In addition, tests performed before discharge were improved.

Ameliorative effect of taurine-chloramine in azathioprine-induced testicular damage; a deeper insight into the mechanism of protection.

BACKGROUND: The male reproductive system is a sensitive and intricate process that can be distressed following exposure to various toxicants. Therapeutic drugs, especially chemotherapeutics, can also adversely affect male fertility by instigating hormonal changes leading to testicular cells injury. Azathioprine (AZA) is an effective anticancer drug, but some cases of testicular toxicity have been reported. The aim of this work was to investigate the protective effects of taurine chloramine (TAU-Cl), a reported antioxidant and antiinflammtory peptide, against AZA-induced testicular dysfunction in male rats and ascertain the contributing mechanisms. METHODS: Forty male rats were allocated into four equal groups; (i) normal control rats, (ii) TAU-Cl group (100 mg/kg b.w/day for 10 weeks, (iii) AZA group (5 mg/day for 4 weeks); (iv) TAU-Cl/AZA group. RESULTS: AZA caused increased DNA damage in the testes, and alterations in sex hormones and sperm quality, including sperm count, viability, and motility. Moreover, testicular tissue from the AZA-treated group had increased levels of oxidative stress indicator, MDA, and decreased activity of the antioxidant enzymes as superoxide dismutase (SOD), reduced glutathione (GSH) and catalase (CAT) levels. These deleterious events were accompanied by upregulated levels of the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-α), and protein expression of iNOS and NFκB-p65, interleukin-1beta (IL-1ß), and proapoptotic marker; caspase-9, together with decreased Bcl-2, NrF2 and hemeoxygenase (HO-1) expression. In contrast, TAU-Cl pretreatment significantly abrogated these toxic effects which were confirmed histologically. CONCLUSION: Pretreatment with TAU-Cl exerts a protective effect against AZA-induced male reproductive testicular atrophy. This finding could open new avenues for the use of TAU-Cl as a complementary approach to chemotherapy supportive care.

Síndrome de obstrucción sinusoidal hepática secundario a toxicidad por azatioprina / Azathioprine-induced hepatic sinusoidal obstruction syndrome

No disponible

Nucleoside diphosphate-linked moiety X-type motif 15 C415T variant as a predictor for thiopurine-induced toxicity in Indian patients.

BACKGROUND AND AIM: Interindividual variation seen in the thiopurine metabolism is attributed to the genetic variant in thiopurine methyltransferase (TPMT) gene leading to myelosuppression. In Asians, the thiopurine-induced toxicity is not completely explained by TPMT variants. Literature indicates that a newer genetic variant in nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15) gene is associated with thiopurine intolerance. We aimed to determine the risk allele frequency of NUDT15 genetic variant and its association with thiopurine-induced toxicity in Indian patients. METHODS: In this pilot study, 69 patients on thiopurine therapy were analyzed. The frequencies of thiopurine-induced leukopenia were recorded. NUDT15 (C415T) and TPMT (*2, *3A, *3B, and *3C) genotyping was performed using amplification refractory mutation system-polymerase chain reaction and restriction fragment length polymorphism technique. Results were validated by DNA sequencing. RESULTS: The NUDT15 CC, CT, and TT genotypes were found to be 86.9%, 11.5%, and 1.5%, respectively, whereas TPMT genetic variants were absent. Of 60 patients without NUDT15 variant, none developed leukopenia, whereas of nine patients with NUDT15 variant, six developed leukopenia (P-value < 0.0001). The mean thiopurine dose of 1.01 and 0.73 mg/kg/day for patients with wild and mutant NUDT15 alleles, respectively, was statistically significant (P < 0.01). The sensitivity and specificity for NUDT15 variant were 100% and 95.2%, respectively. CONCLUSIONS: The NUDT15 risk allele frequency was 7.2%. There are 6/69 (8.7%) patients who developed leukopenia and harbored NUDT15 variant, thus showing a strong association for thiopurine-induced toxicity. Hence, NUDT15 genotyping may be considered before thiopurine therapy in Indian patients.

Model-based contextualization of in vitro toxicity data quantitatively predicts in vivo drug response in patients.

Understanding central mechanisms underlying drug-induced toxicity plays a crucial role in drug development and drug safety. However, a translation of cellular in vitro findings to an actual in vivo context remains challenging. Here, physiologically based pharmacokinetic (PBPK) modeling was used for in vivo contextualization of in vitro toxicity data (PICD) to quantitatively predict in vivo drug response over time by integrating multiple levels of biological organization. Explicitly, in vitro toxicity data at the cellular level were integrated into whole-body PBPK models at the organism level by coupling in vitro drug exposure with in vivo drug concentration-time profiles simulated in the extracellular environment within the organ. PICD was exemplarily applied on the hepatotoxicant azathioprine to quantitatively predict in vivo drug response of perturbed biological pathways and cellular processes in rats and humans. The predictive accuracy of PICD was assessed by comparing in vivo drug response predicted for rats with observed in vivo measurements. To demonstrate clinical applicability of PICD, in vivo drug responses of a critical toxicity-related pathway were predicted for eight patients following acute azathioprine overdoses. Moreover, acute liver failure after multiple dosing of azathioprine was investigated in a patient case study by use of own clinical data. Simulated pharmacokinetic profiles were therefore related to in vivo drug response predicted for genes associated with observed clinical symptoms and to clinical biomarkers measured in vivo. PICD provides a generic platform to investigate drug-induced toxicity at a patient level and thus may facilitate individualized risk assessment during drug development.

Red blood cell Pig-a assay and PIGRET assay in rats with azathioprine.

A new in vivo gene mutation assay has been developed based on the phosphatidylinositol glycan anchor biosynthesis, Class A gene (Pig-a in rodents) as an endogenous reporter. Using this Pig-a assay, the in vivo mutagenicity of a single dose of azathioprine (Aza) was investigated in red blood cells (RBC Pig-a assay) and reticulocytes (PIGRET) of rats. Eight-week old male rats were orally dosed once with Aza at 50, 100 and 200mg/kg or ethylnitrosourea (ENU) at 10 and 40mg/kg as a positive control. Because 4 out of 6 animals at 200mg/kg of Aza died 3days after the dosing, this dose group was excluded for analyses. The frequencies of Pig-a mutants in RBCs and reticulocytes (RET) were evaluated once a week for 4 weeks after the treatment. With a single exposure to ENU, the frequencies of Pig-a mutants in both RBCs and RETs increased in a time- and dose-dependent manner. In contrast, with Aza small effects that were not statistically significant were observed in rats at 21 and 14days in the RBC Pig-a and PIGRET assays respectively. Based on the present results, the mutagenic potential of Aza is negligible after single oral administration in rats.

Azathioprine induction of tumors with microsatellite instability: risk evaluation using a mouse model.

Mismatch-repair (MMR)-deficient cells show increased in vitro tolerance to thiopurines because they escape apoptosis resulting from MMR-dependent signaling of drug-induced DNA damage. Prolonged treatment with immunosuppressants including azathioprine (Aza), a thiopurine prodrug, has been suggested as a risk factor for the development of late onset leukemias/lymphomas displaying a microsatellite instability (MSI) phenotype, the hallmark of a defective MMR system. We performed a dose effect study in mice to investigate the development of MSI lymphomas associated with long term Aza treatment. Over two years, Aza was administered to mice that were wild type, null or heterozygous for the MMR gene Msh2. Ciclosporin A, an immunosuppressant with an MMR-independent signaling, was also administered to Msh2(wt) mice as controls. Survival, lymphoma incidence and MSI tumor phenotype were investigated. Msh2(+/-) mice were found more tolerant than Msh2(wt) mice to the cytotoxicity of Aza. In Msh2(+/-) mice, Aza induced a high incidence of MSI lymphomas in a dose-dependent manner. In Msh2(wt) mice, a substantial lifespan was only observed at the lowest Aza dose. It was associated with the development of lymphomas, one of which displayed the MSI phenotype, unlike the CsA-induced lymphomas. Our findings define Aza as a risk factor for an MSI-driven lymphomagenesis process.

Role of oxidative stress mediated by glutathione-s-transferase in thiopurines' toxic effects.

Azathioprine (AZA), 6-mercaptopurine (6-MP), and 6-thioguanine (6-TG) are antimetabolite drugs, widely used as immunosuppressants and anticancer agents. Despite their proven efficacy, a high incidence of toxic effects in patients during standard-dose therapy is recorded. The aim of this study is to explain, from a mechanistic point of view, the clinical evidence showing a significant role of glutathione-S-transferase (GST)-M1 genotype on AZA toxicity in inflammatory bowel disease patients. To this aim, the human nontumor IHH and HCEC cell lines were chosen as predictive models of the hepatic and intestinal tissues, respectively. AZA, but not 6-MP and 6-TG, induced a concentration-dependent superoxide anion production that seemed dependent on GSH depletion. N-Acetylcysteine reduced the AZA antiproliferative effect in both cell lines, and GST-M1 overexpression increased both superoxide anion production and cytotoxicity, especially in transfected HCEC cells. In this study, an in vitro model to study thiopurines' metabolism has been set up and helped us to demonstrate, for the first time, a clear role of GST-M1 in modulating AZA cytotoxicity, with a close dependency on superoxide anion production. These results provide the molecular basis to shed light on the clinical evidence suggesting a role of GST-M1 genotype in influencing the toxic effects of AZA treatment.

The transferability from rat subacute 4-week oral toxicity study to translational research exemplified by two pharmaceutical immunosuppressants and two environmental pollutants with immunomodulating properties.

Exposure to chemicals may have an influence on the immune system. Often, this is an unwanted effect but in some pharmaceuticals, it is the intended mechanism of action. Immune function tests and in depth histopathological investigations of immune organs were integrated in rodent toxicity studies performed according to an extended OECD test guideline 407 protocol. Exemplified by two immunosuppressive drugs, azathioprine and cyclosporine A, and two environmental chemicals, hexachlorobenzene and benzo[a]pyrene, results of subacute rat studies were compared to knowledge in other species particular in humans. Although immune function has a high concordance in mammalian species, regarding the transferability from rodents to humans various factors have to be taken into account. In rats, sensitivity seems to depend on factors such as strain, sex, stress levels as well as metabolism. The two immunosuppressive drugs showed a high similarity of effects in animals and humans as the immune system was the most sensitive target in both. Hexachlorobenzene gave an inconsistent pattern of effects when considering the immune system of different species. In some species pronounced inflammation was observed, whereas in primates liver toxicity seemed more obvious. Generally, the immune system was not the most sensitive target in hexachlorobenzene-treatment. Immune function tests in rats gave evidence of a reaction to systemic inflammation rather than a direct impact on immune cells. Data from humans are likewise equivocal. In the case of benzo[a]pyrene, the immune system was the most sensitive target in rats. In the in vitro plaque forming cell assay (Mishell-Dutton culture) a direct comparison of cells from different species including rat and human was possible and showed similar reactions. The doses in the rat study had, however, no realistic relation to human exposure, which occurs exclusively in mixtures and in a much lower range. In summary, a case by case approach is necessary when testing immunotoxicity. Improvements for the translation from animals to humans related to immune cells can be expected from in vitro tests which offer direct comparison with reactions of human immune cells. This may lead to a better understanding of results and variations seen in animal studies.

Integrated analysis of toxicity data of two pharmaceutical immunosuppressants and two environmental pollutants with immunomodulating properties to improve the understanding of side effects-A toxicopathologist׳s view.

Data in a toxicity test are evaluated generally per parameter. Information on the response per animal in addition to per parameter can improve the evaluation of the results. The results from the six studies in rats, described in the paper by Kemmerling, J., Fehlert, E., Rühl-Fehlert, C., Kuper, C.F., Stropp, G., Vogels, J., Krul, C., Vohr, H.-W., 2015. The transferability from rat subacute 4-week oral toxicity study to translational research exemplified by two pharmaceutical immunosuppressants and two environmental pollutants with immunomodulating properties (In this issue), have been subjected to principal component analysis (PCA) and principal component discriminant analysis (PC-DA). The two pharmaceuticals azathioprine (AZA) and cyclosporine A (CSA) and the two environmental pollutants hexachlorobenzene (HCB) and benzo(a)pyrene (BaP) all modulate the immune system, albeit that their mode of immunomodulation is quite diverse. PCA illustrated the similarities between the two independent studies with AZA (AZA1 and AZA2) and CSA (CSA1 and CSA2). The PC-DA on data of the AZA2 study did not increase substantially the information on dose levels. In general, the no-effect levels were lower upon single parameter analysis than indicated by the distances between the dose groups in the PCA. This was mostly due to the expert judgment in the single parameter evaluation, which took into account outstanding pathology in only one or two animals. The PCA plots did not reveal sex-related differences in sensitivity, but the key pathology for males and females differed. The observed variability in some of the control groups was largely a peripheral blood effect. Most importantly, PCA analysis identified several animals outside the 95% confidence limit indicating high-responders; also low-to-non-responders were identified. The key pathology enhanced the understanding of the response of the animals to the four model compounds.

Azathioprine does not reduce adenoma formation in a mouse model of sporadic intestinal tumorigenesis.

AIM: To investigate if azathioprine could reduce adenoma formation in Apc(Min/+) , a mouse model of sporadic intestinal tumorigenesis. METHODS: Azathioprine was administered via drinking water (estimated 6-20 mg/kg body weight per day) to Apc(Min/+) and wildtype mice. Control animals received vehicle only (DMSO) dissolved in drinking water. At 15 wk of age all mice were sacrificed and intestines of Apc(Min/+) were harvested for evaluation of polyp number. Azathioprine induced toxicity was investigated by immunohistochemical analysis on spleens. RESULTS: All azathioprine treated mice showed signs of drug-associated toxicity such as weight loss and development of splenic T-cell lymphomas. Although this suggests that the thiopurine concentration was clearly in the therapeutic range, it did not reduce tumor formation (48 ± 3.1 adenomas vs 59 ± 5.7 adenomas, P = 0.148). CONCLUSION: We conclude that in the absence of inflammation, azathioprine does not affect intestinal tumorigenesis.

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.

Involvement of oxidative stress and immune- and inflammation-related factors in azathioprine-induced liver injury.

Drug-induced liver injury (DILI) is a growing concern in the fields of drug development and clinical drug therapy because numerous drugs have been linked to hepatotoxicity. However, it is difficult to predict DILI in humans due to the lack of experimental animal models. Although azathioprine (AZA), which is a widely used immunosuppressive drug, is generally well tolerated, a small number of patients prescribed AZA develop severe hepatitis. However, the mechanism underlying this process has not yet been elucidated. In this study, we developed a mouse model of AZA-induced liver injury and investigated the mechanisms responsible for the hepatotoxicity of AZA. Female BALB/c mice were orally administered AZA. After AZA administration, the plasma levels of alanine aminotransferase and aspartate aminotransferase were increased, and liver damage was confirmed through a histological evaluation. In addition, the hepatic glutathione levels and superoxide dismutase activity were significantly decreased. The plasma levels of reactive oxygen species were significantly increased during the early phase of AZA-induced liver injury, and the hepatic mRNA levels of immune- and inflammation-related factors were also significantly changed. In conclusion, oxidative stress and the subsequently activated immune- and inflammation-related factors are involved in AZA-induced liver injury.

An integrated proteomic and transcriptomic approach to understanding azathioprine- induced hepatotoxicity in rat primary hepatocytes.

Azathioprine, an immunosuppressant, has gained a prominent position in the clinic for prevention of graft rejection in organ transplants, as well as dermatological autoimmune diseases. However, according to a number of research reports, hepatotoxicity, as one of the side effects, is a major obstacle in azathioprine therapy. In this study, an integrated toxicoproteomic and toxicotranscriptomic analysis was performed using rat primary hepatocytes, in order to gain insight into the in-depth pathway map related to azathioprine-induced hepatotoxicity. For proteomic and transcriptomic analysis, rat primary hepatocytes were exposed to azathioprine at IC20 concentration for 24 h. In particular, 2D LC-MS/MS and informatics-assisted label-free strategy for proteomic analysis were applied in order to increase the number of identified proteins and to improve the confidence of the quantitation results. Among 119 differentially identified protein species, 69 were upregulated and 50 were downregulated in the azathioprine-treated group. At the mRNA level, results of transcriptomic analysis showed increased transcription of 340 genes and decreased transcription of 63 genes in the azathioprine-treated group. Based on the analysis of transcriptomic and proteomic results using the DAVID program, drug metabolism/oxidative stress enzymes, xenobiotic metabolism by cytochrome P450, fatty acid metabolism, primary bile acid biosynthesis, contraction, inflammation metabolism, and mitogen-activated protein kinase (MAPK) kinase (ERK/JNK/p38 kinase) pathways were affected in azathioprine-treated hepatotoxicity. The effects on genes and proteins related to several important pathways were confirmed by real-time PCR and immunoblot analysis, respectively. This study is the first to report on relevant pathways related to azathioprine-induced hepatotoxicity through performance of integrated transcriptomic and proteomic analyses.

Infliximab exerts no direct hepatotoxic effect on HepG2 cells in vitro.

BACKGROUND: Infliximab-induced hepatotoxicity is reported in several case studies involving patients with inflammatory bowel disease (IBD) and a direct hepatotoxic effect has been proposed. OBJECTIVE: The aim of this study was to determine the direct in vitro toxicity of infliximab. As a proof of principle the in vitro toxicity of thiopurines and methotrexate was also determined. METHODS: Cell survival curves and the half maximal inhibitory concentrations (IC(50)) were obtained after 24, 48 and 72 h of incubation in HepG2 cells with the IBD drugs azathioprine, 6-mercaptopurine, 6-thioguanine, methotrexate or infliximab by using the WST-1 cytotoxicity assay. RESULTS: No in vitro hepatotoxicity in HepG2 cells was seen with infliximab, while concentration-dependent cytotoxicity was observed when HepG2 cells were incubated with increasing concentrations of azathioprine, 6-mercaptopurine and 6-thioguanine. CONCLUSION: Infliximab alone or given in combination with azathioprine showed no direct hepatotoxic effect in vitro, indicating that the postulated direct hepatotoxicity of infliximab is unlikely.

[Peculiarities of extraction of 6-mercaptopurine and azathioprine from aqueous saline solutions].

The results of extraction of 6-mercaptopurine and azathioprine from aqueous saline solutions with organic solvents of different chemical nature and their mixtures are presented. Synergism between the distribution coefficients was demonstrated during the extraction of the above compounds with 1,4-dioxane and chloroform mixtures. The use of a chloroform--1,4-dioxane system in the molar ratio of 0.8:0.2 as a solvent resulted in the maximum values of distribution coefficients of 6-mercaptopurine and azathioprine.