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Drug use during pregnancy is an important issue that must be investigated due to its adverse effects on maternal and foetal health. This study aimed to determine the embryotoxic and teratogenic effects of in-ovo administered metamizole (dipyrone), which can be used when needed during pregnancy and has potent analgesic, antipyretic, anti-inflammatory, and long bone (tibia and femur) effects. This study used 240 fertile eggs from Atak S breed chickens, divided into eight equal groups: control, vehicle control, and 15.62, 31.25, 62.5, 125, 250 and 500 mg/kg metamizole. The eggs were hatched on the 21st day of incubation, and the chicks' body weights and mortality rates were determined. The right and left femur and tibia bones were resected from the chicks. Anatomical reference points were determined after removing the soft tissues of the bones, and necessary morphometric measures were taken from these points with a 0.01 mm precision using digital callipers. The 100% lethal dose (LD 100 ) was identified in the highest examined dose (500 mg/kg) in the Chicken Embryotoxicity Screening Test (CHEST)-I stage. The CHEST-II stage determined the 50% lethal dose (LD 50 ). High-dose metamizole affected skeletal development, significantly decreasing tibia and femur lengths and corpus thicknesses and increasing mortality., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

Background: Metamizole is banned in some countries because of its toxicity, although it is widely used in some European countries. In addition, there is limited information on its safety profile, and it is still debated whether it is toxic to the heart, lungs, liver, kidneys, and stomach., Aims: Our study investigated the effects of metamizole on the heart, lung, liver, kidney, and stomach tissues of rats., Methods: Eighteen rats were divided into three groups, wassix healthy (HG), 500 mg/kg metamizole (MT-500), and 1000 mg/kg metamizole (MT-1000). Metamizole was administered orally twice daily for 14 days. Meanwhile, the HG group received pure water orally. Biochemical, histopathologic, and macroscopic examinations were performed on blood samples and tissues., Results: Malondialdehyde (MDA), total glutathione (tGSH), superoxide dismutase (SOD), and catalase (CAT) in the lung and gastric tissues of MT-500 and MT-1000 groups were almost the same as those of the HG (p > 0.05). However, MDA levels in the heart and liver tissues of MT-500 and MT-1000 groups were higher (p < 0.05) compared to the HG, while tGSH levels and SOD, and CAT activities were lower (p < 0.05). MDA levels of MT-500 and MT-1000 groups in the kidney tissue increased the most (p < 0.001), and tGSH levels and SOD and CAT activities decreased the most (p < 0.001) compared to HG. Metamizole did not cause oxidative damage in the lung and gastric tissue. While metamizole did not change troponin levels, it significantly increased alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), and creatinine levels compared to HG. Histopathologically, mild damage was detected in heart tissue, moderate damage in liver tissue, and severe damage in renal tissue. However, no histopathologic damage was found in any groups' lung and gastric tissues., Conclusion: Metamizole should be used under strict control in patients with cardiac and liver diseases and it would be more appropriate not to use it in patients with renal disease., (© 2024. The Author(s).)

Dipyrone is an analgesic and antipyretic drug commonly used in many countries. Although generally not recommended during pregnancy, it is known that many women use dipyrone during the gestational period. In this study, we investigated the endocrine and reproductive effects of dipyrone in female and male offspring rats exposed in utero from gestational days 10-21. Pregnant rats were treated with dipyrone at 25, 75, and 225 mg/kg/day via oral gavage. Developmental landmarks-anogenital index (AGI), number of nipples, vaginal opening, first estrus, and preputial separation-were evaluated in the offspring. Reproductive parameters, including estrous cycle regularity, daily sperm production, weight and histopathology of reproductive organs, steroid hormone levels, and gene expression of selected markers of reproductive function were assessed at adulthood. At the highest dose, dipyrone induced a significant increase in postimplantation losses/fetal death and delayed parturition in dams. Offspring exposed in utero to the highest dose also exhibited significant changes in some early life markers of endocrine disruption, in particular increased AGI in females, indicating a proandrogenic effect, and increased rate of retained nipples in males, indicating an antiandrogenic response. No changes were observed in markers of puberty onset or reproductive parameters at adulthood. These results suggest that exposure to therapeutically relevant doses of dipyrone may induce mild endocrine disruptive effects that can be detected in late pregnancy and early life. Such effects may be relevant considering dipyrone use by pregnant women and the possibility of coexposures with other endocrine disruptors., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Dipyrone is a commonly used analgesic in many countries and there is limited data on its possible endocrine disrupting effects. We performed a screening for in vivo and in vitro anti(estrogenic) activity of dipyrone. For the in vivo uterotrophic assay, immature female rats (22-days-old) were treated daily by oral gavage for three days with different doses of dipyrone alone (50, 100, 200 mg/kg/day) and associated with three ethynylestradiol (EE) doses (1, 3 and 10 μg/kg/day), which were based on a dose-response curve experiment. The uterine weight was used as a biomarker for estrogenicity. In a parallel in vitro approach, we used a yeast-based transcriptional activation reporter gene assay (Yeast Estrogen Screening - YES) for assessment of estrogenic agonistic and antagonistic effects of dipyrone and its main metabolites 4-methylaminoantipyrine (MAA) and 4-aminoantipyrine (AA). In the uterotrophic assay, animals that received EE at 1, 3 and 10 μg/kg/day showed an increase in relative uterine weight compared with vehicle-only rats (canola oil). Dipyrone did not increase uterine weight at any dose tested (50, 100 and 200 mg/kg/day) in relation to vehicle control, indicating absence of estrogenic activity. Furthermore, co-administration of dipyrone (50 and 200 mg/kg/day) and EE (1, 3 or 10 μg/kg/day) was unable to block EE estrogenic action in comparison to the groups treated with EE alone, indicating absence of antiestrogenic activity. In the YES assay dipyrone and its metabolites did not demonstrate estrogen agonistic or antagonistic properties in the yeast cells. These results suggest that dipyrone and its metabolites do not produce (anti)estrogenic effects in vivo or in vitro., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Dipyrone or metamizole is one of the most used analgesics, mainly due to its low financial cost. However, in some countries, the sale of dipyrone is prohibited due to reported severe cases of agranulocytosis as a result of its use. Despite its high use, studies showing genotoxic and cytotoxic effects of dipyrone in mammalian cells are scarce. Therefore, in the present study, we assessed cell viability, genotoxic effects, cytotoxic effects (by apoptosis and necrosis induction), and the induction of reactive oxygen species (ROS) in Vero cells (a cell line obtained from the red kidney of green monkey) exposed to dipyrone. Our results showed a significant reduction in viability of cells exposed to dipyrone by the MTT assay. A significant increase in damage index evaluated by a comet assay was also observed, which indicates its genotoxic effects. In which concerns the cytotoxic effects of dipyrone, we observed a significant increase in the number of apoptotic cells using fluorescent dyes after 24 h and 48 h of treatment with the drug. Our results also showed that there was no significant difference in the induction of ROS generation after treatment of the cells with the drug assessed by the DCFH-DA assay. Thus, our work showed that dipyrone is both a genotoxic and cytotoxic drug to Vero cells in the assessed conditions.

Metamizole is an analgesic and antipyretic with a superior analgesic efficacy than paracetamol. Since metamizole can cause neutropenia and agranulocytosis, it is currently used in only few countries. In a previous study, we have shown that N-methyl-4-aminoantipyrine (MAA), the active metamizole metabolite, reacts with hemin and forms an electrophilic metabolite that is toxic for HL60 cells, but not for mature neutrophil granulocytes. In the current study, we investigated the toxicity of hemin (12.5 μM) and MAA (100 μM) on differentiating HL60 cells. In undifferentiated HL60 cells, hemin decreased the viability and this effect was significantly increased by MAA. Similarly, hemin/MAA was more toxic than hemin alone on human cord blood cells. At 3 days (metamyelocyte stage) and 5 days of differentiation (mature neutrophils), hemin/MAA was not toxic on HL60 cells, whereas hemin alone was still toxic. No toxicity was observed on freshly isolated human neutrophils. The protein expression of enzymes responsible for hemin metabolism increased with HL60 cell differentiation. Inhibition of heme oxygenase-1 or cytochrome P450 reductase increased the toxicity of hemin and hemin/MAA in undifferentiated, but only for hemin in differentiated HL60 cells. Similar to the enzymes involved in hemin metabolism, the protein expression of enzymes involved in antioxidative defense and the cellular glutathione pool increased with HL60 cell differentiation. In conclusion, HL60 cells become resistant to the toxicity of hemin/MAA and partly also of hemin during their differentiation. This resistance is associated with the development of heme metabolism and of the antioxidative defense system including the cellular glutathione pool., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Metamizole is an analgesic and antipyretic, but can cause neutropenia and agranulocytosis. We investigated the toxicity of the metabolites N-methyl-4-aminoantipyrine (MAA), 4-aminoantipyrine (AA), N-formyl-4-aminoantipyrine (FAA) and N-acetyl-4-aminoantipyrine (AAA) on neutrophil granulocytes and on HL60 cells (granulocyte precursor cell line). MAA, FAA, AA, and AAA (up to 100 µM) alone were not toxic for HL60 cells or granulocytes. In the presence of the myeloperoxidase substrate H 2 O 2 , MAA reduced cytotoxicity for HL60 cells at low concentrations (<50 µM), but increased cytotoxicity at 100 µM H 2 O 2 . Neutrophil granulocytes were resistant to H 2 O 2 and MAA. Fe 2+ and Fe 3+ were not toxic to HL60 cells, irrespective of the presence of H 2 O 2 and MAA. Similarly, MAA did not increase the toxicity of lactoferrin, hemoglobin or methemoglobin for HL60 cells. Hemin (hemoglobin degradation product containing a porphyrin ring and Fe 3+ ) was toxic on HL60 cells and cytotoxicity was increased by MAA. EDTA, N-acetylcystein and glutathione prevented the toxicity of hemin and hemin/MAA. The absorption spectrum of hemin changed concentration-dependently after addition of MAA, suggesting an interaction between Fe 3+ and MAA. NMR revealed the formation of a stable MAA reaction product with a reaction pathway involving the formation of an electrophilic intermediate. In conclusion, MAA, the principle metabolite of metamizole, increased cytotoxicity of hemin by a reaction involving the formation of an electrophilic metabolite. Accordingly, cytotoxicity of MAA/hemin could be prevented by the iron chelator EDTA and by the electron donors NAC and glutathione. Situations with increased production of hemin may represent a risk factor for metamizole-associated granulocytopenia., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Mild analgesics have been associated with antiandrogenic effects, but there are no such studies on dipyrone, despite its high prevalence of use in many countries. We examined the production of steroid hormones in human H295R cells after exposure to dipyrone and two metabolites, 4-Methylaminoantipyrine (MAA) and 4-Aminoantipyrine (AA), as well as fetal testicular testosterone production in rats following maternal dipyrone exposure. Androgen agonistic/antagonistic effects were examined in vitro for dipyrone and its metabolites in the Yeast Androgen Screen (YAS) assay and in vivo for dipyrone through the Hershberger assay. In vitro we tested dipyrone, MAA, and AA (0.1-1000 μM) while in vivo we used dipyrone (50, 100, 200 mg/kg/day). In the H295R assay, dipyrone, MAA and AA reduced the production of androgens and corticosteroids. Testosterone was reduced at concentrations 4-13 times higher than the maximum plasma concentrations reported in humans for MAA and AA. No effects were observed in the fetal testosterone production assay. In the YAS and Hershberger assays, no androgen agonistic/antagonistic activities were observed. These results indicate that dipyrone and its metabolites do not interact with the androgen receptor, but have the potential to inhibit steroidogenesis, however only at concentrations that are not relevant under normal medical use., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Dipyrone (metamizole), a powerful drug, is widely used as an analgesic and antipyretic; however, the safety of its use during lactation and the potential impact on the offspring are not well established. This study aimed to determine the effect of maternal dipyrone treatment during lactation on offspring development and emotional behavior and on the dam's maternal behavior. Hence, on postnatal day (PND) 2, drinking water only or drinking water containing dipyrone at doses of 100, 300, and 500mg/kg/day, were offered to lactating mothers up to PND9. Thereafter, all mice were provided regular drinking water. On PND2, all litters were culled to 8 pups (4 males and 4 females). Maternal behavior was evaluated at PND3, 6, 9, and 12, and at PND7 we evaluated locomotor activity in the open field. Reflex parameters and physical development of offspring were evaluated during lactation. At PND7, analysis of ultrasonic vocalization (USV) was performed. When the animals reached adolescence, we evaluated their performance in the open field, elevated plus maze (EPM), and marble burying. Our data demonstrated that maternal dipyrone treatment during lactation not only altered maternal behavior and the onset of physical and neurodevelopmental landmarks but also had an impact on anxiety-like behavior in offspring., (Copyright © 2017 ISDN. Published by Elsevier Ltd. All rights reserved.)

Metamizole (dipyrone) is a first-line, non-opioid analgesic used for postoperative pain management. Clinical data and animal experiments indicate a possible vasodilator action of this drug. We investigated the effects of metamizole on human artery and vein tone in an ex vivo model to assess potential contributions to venous pooling. Excess segments of bypass grafts were harvested during coronary artery bypass grafting procedures. Tensions were measured in an organ bath for 120 min after adding metamizole to the preconstricted vessels. Contribution of endothelium was assessed in endothelium-denuded vessels, and indometacin was used to identify cyclooxygenase-mediated effects. Internal mammary arteries (n = 6) constricted after addition of 1, 3, and 10 μM metamizole and remained constricted at the lower doses. Transient constrictions also occurred in saphenous veins (n = 20), but veins relaxed below solvent controls after 20 min at all concentrations. Endothelium removal (n = 12) and cyclooxygenase inhibition (n = 12) suppressed the vasoconstrictor effect but not the vasodilator effect. Metamizole and its metabolites display counteracting effects on blood vessel tone ex vivo. The vasoconstrictor effect is mediated by cyclooxygenase-derived products. The net effect is site-specific, resulting in a selective venous vasodilator action. This may exacerbate unwanted venous pooling during postoperative pain therapy.

Aim: The aim of this study was to investigate the effects of metamizole sodium on neural tube development in the early stage chick embryo model that complies with the first month of embryonic development in mammals., Material and Methods: A total of 40 fertilized chicken eggs were divided into 4 equal groups. The eggs were incubated in the incubator at a temperature of 37.8±2°C with 60±5% humidity. Group A was the control, Group B was administered physiological saline, Group C was administered 30 mg/kg metamizole sodium (based on the therapeutic index range of it used in humans) and Group D was administered 90 mg/kg metamizole sodium. All embryos were removed from the egg at the 48th hour and morphologically and histologically examined., Results: Normal development was seen and the neural tube was closed in 17 embryos in Groups A and B. A neural tube defect was seen in 2 embryos in group A and in 1 embryo in group B. A neural tube closure defect was seen in all embryos in group C and 9 embryos in group D. There was 1 dead embryo in Group D., Conclusion: Metamizole sodium was seen to produce a neural tube defect in the chicken embyro model.

We present the case of a 63 year old man who died of severe septic shock in the setting of agranulocytosis induced by dipyrone (metamizole). The patient had previously developed agranulocytosis after dipyrone exposure 18 months prior to this. The case illustrates the seriousness of dipyrone-induced agranulocytosis, highlights the risks associated with re-exposure and underlines the need for excellent communication between treating physicians and their patients. The possible underlying mechanisms, epidemiology and management of dipyrone-induced agranulocytosis are discussed.

The use of the non-steroidal anti-inflammatory drugs such as dipyrone is so widespread that this drug and its metabolites have been detected in effluents and surface water. This study aimed to evaluate the potential toxic effects of dipyrone on the aquatic environment, using a native fish species, Rhamdia quelen. Fish were exposed to three concentrations of dipyrone, 0.5, 5 and 50 μg/L, in the water for 15 days, and hematological, biochemical, genetic and morphological biomarkers were evaluated. The glutathione S-transferase activity decreased in the highest concentration in relation to the control group. In addition, hematocrit, red blood cells and thrombocyte counts were decreased in all three exposed groups in relation to the control group. The comet assay showed DNA damage at the lowest concentration of dipyrone and significant kidney damage. Those results suggest that a constant exposure of aquatic organisms to dipyrone presents potential toxic effects., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The photochemical behaviour of three relevant metabolites of the analgesic and antipyretic drug dipyrone, 4-methylaminoantipyrine (4-MAA), 4-formylaminoantipyrine (4-FAA) and 4-acetylaminoantipyrine (4-AAA), was evaluated under simulated solar irradiation (Suntest system). For 4-MAA, different aqueous solutions (synthetic seawater, freshwater and Milli-Q water) as well as different operational conditions were compared. According to the experimental results, 4-MAA resulted as being an easily degraded molecule by direct photolysis, with half-life times (t1/2) ranging from 0.12 to 0.58 h, depending on the irradiation conditions. Faster degradation was observed in synthetic waters, suggesting that the photolysis was influenced by the salt composition of the waters. However, no effect on the degradation rate was observed by the presence of natural photosensitizers (dissolved organic matter, nitrate ions). 4-FAA and 4-AAA showed slower photodegradation kinetics, with t1/2 of 24 and 28 h, respectively. A study of photoproduct identification was carried out by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS) (ESI positive mode), which allowed us to propose a tentative photodegradation pathway for 4-MAA and the identification of persistent by-products in all the cases. Finally, the application of an acute toxicity test (Daphnia magna) showed an increase in toxicity during the photolytic process, a consequence of the formation of toxic photoproducts.

Dipyrone is a non-narcotic analgesic and antipyretic drug used in both pediatric and adult patients. Dipyrone solution can be used intranasally as an antipyretic agent for infants. However, dipyrone is not stable in liquid state. Therefore, a stable dipyrone formulation was developed and the antipyretic effect of the formulation was studied after intranasal administration in rabbits and rats, respectively. To guarantee dose accuracy in animal studies, effect of dose volume on the distribution of dipyrone solution in rabbit nasal cavities were studied, using gentian violet as an indicator. Animal fever model and intranasal administration methods were established. In addition, the potential toxicity of the dipyrone formulation was studied. It was shown that the nasal volume of rabbits is large enough to hold 100 microl solution. After intranasal administration, improved pharmacodynamics was obtained with the new developed dipyrone formulation compared to the normal dipyrone solution, and significantly decreased body temperature was observed 10 min after dosing. The toxicity was negligible. In conclusion, the dipyrone formulation is effective and safe for clinical medication.

A complex approach based on the use of test organisms belonging to different systematic groups (plants, invertebrates and vertebrates), as well as the nucleolar biomarker and the micronucleus test on their cells, was applied to assess the toxicity, cytotoxicity and genotoxicity of two pharmaceutical substances (metamizole sodium and acetylsalicylic acid) applied at ic(50) concentrations for mammalian cells. The compound acetylsalicylic acid was evaluated at a concentration (1.6 x 10(3) mg l(-1)) that was non-toxic for bioassays based on fish (Carassius auratus gibelio) and hydra (Hydra attenuata) and acutely toxic for bioassays with ceriodaphnia (Ceriodaphnia affinis) and onion (Allium cepa). The metamizole sodium solution (6.25%) demonstrated acute toxicity for the whole set of test organisms. Both drugs, after their 30-360 min influence on the test organisms, first changed the nucleolar size in plant and animal cells (i.e. the transcriptional activity of ribosomal genes was affected most significantly). Moreover, the metamizole sodium solution caused nucleolar structural damage in 90% of hydra cells as early as after 30 min of exposure. The acetylsalicylic acid solution inhibited essentially the rate of cell division in the meristem of onion roots (the mitotic index decreased to 9.6 per thousand, as compared 51.7 per thousand for the control). The carp incubation and the onion germination in the acetylsalicylic acid solution showed a reproducible increase in the frequency of cells with micronuclei (2 and 5.5 times, respectively) and double nuclei (3 and 1.5 times, respectively). The approach described herein may be applied for obtaining rapid, cost-efficient and useful supplementary data on different types of toxicity for marketed drugs as well as for drugs under development.

Phenylbutazone (PB), oxyphenbutazone (OPB), antipyrine (AP) and dipyrone (DP) are four important pyrazolone derivatives mainly used as anti-inflammatory, antipyretic and analgesic drugs. At present these are the most widely used pyrazolone derivatives throughout the world. The widespread use of these drugs are of great concern for human health problems. In the present study these four drugs were tested in mutagenicity assays in Salmonella strains TA97a, TA98, TA100 and TA102 using a plate incorporation assay both with and without S-9 mix and for in vivo sister chromatid exchanges (SCE) in bone marrow cells of mice. The first three drugs were negative in all the tester strains but dipyrone showed a weak mutagenic activity at higher concentrations in all four strains both with and without metabolic activation. In the in vivo SCE assay in male mice, all four drugs showed a statistically significant increase in SCE in bone marrow cells when compared with control., (Copyright 1998 Elsevier Science B.V.)

In the present study we investigated the influence of several nonsteroidal anti-inflammatory drugs on calcium efflux in isolated rat renal cortex mitochondria in order to assess their potential to disrupt cell calcium homeostasis, as well as aspects of the mechanisms associated with oxidation of mitochondrial pyridine nucleotides (NAD(P)H) and with inhibition of the process by cyclosporin A (CsA). Calcium efflux was estimated with arsenazo III as an indicator and the redox state of NAD(P)H was monitored fluorimetrically at the 366/450 nm excitation/emission wavelength pair. Dipyrone, paracetamol and ibuprofen did not induce calcium efflux even at 1 mM, piroxicam and salicylate were poor inducers, while diclofenac sodium and mefenamic acid were potent inducers releasing calcium even at 20 microM and 10 microM, respectively. In the presence of 10 microM calcium, CsA had no appreciable effect while in the presence of 30 microM calcium it delayed calcium efflux. Oxidation of mitochondrial NAD(P)H, concomitant with calcium efflux and inhibited by CsA, was observed only in the presence of 30 microM calcium. The results suggest that diclofenac sodium and mefenamic acid induce calcium efflux in mitochondria through both a mechanism intrinsic to the mitochondrial membrane permeability transition and a mechanism including the electroneutral Ca2+/nH+ porter.

Effect of solutions or suspensions of eight drugs including analgin, paracetamol, propafenone hydrochloride, propranolol hydrochloride, ephedrine hydrochloride, gentamycin sulfate, sodium deoxycholate and hydrocortisone on ciliary movement were evaluated with in vitro or in situ toad palate model and scanning electron microscope. In vitro toad palate model: 0.2 ml of test drug solution or suspension was applied to a piece of freshly dissected upper palate of toad. The mucocilia were examined with an optical microscope and the lasting time of ciliary movement was recorded after drug application. The upper palate was rinsed with physiological saline when the ciliary movement stopped. The lasting time of ciliary movement after rinsing was then recorded again. In situ palate model: 0.5 ml of test drug solution or suspension was applied to the upper palate of toad for 30 min, and rinsed with physiological saline. The palate was dissected out and the operation was carried out in a similar manner. The results showed that the in situ toad palate model is a satisfactory method for studying the ciliotoxicity of drugs. The in vitro toad palate model is unsuitable for suspension and gel. The results of the eight drugs revealed that ciliary movement is frequently affected by many drugs and, therefore, care must be taken in developing any nasal dosage form to ensure its least ciliotoxicity.

The mutagenic effect of analgin was studied in germ and somatic cells of male mice Mus musculus. It was found that injection of analgin (20 and 40 mg per mouse) significantly increased the frequency of sperm head anomalies and chromosome aberrations in bone marrow cells. Immobilization of analgin in starch led to decrease in the drug immobilization.

For assessment of the carcinogenic potential and the mutagenicity of dipyrone, an antipyretic anodyne, -[(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl) methylamino]-methanesulfonic acid sodium salt monohydrate, three experiments were conducted using dipyrone A produced in Japan and/or dipyrone B obtained from the Federal Republic of Germany. (i) Carcinogenic potential of dipyrone A for rat liver: 8 week old male F344 rats were pretreated with 0.01% diethylnitrosamine (DEN) in drinking water for 2 weeks and, after 1 week of resting, administered 0.4% dipyrone in drinking water, 5 days a week, for 72 weeks. After an 8 week recovery period, all surviving rats were killed at 83 weeks. Hepatocellular carcinomas developed at a higher incidence in the DEN + dipyrone group (18 of 29 rats, 62%) than in the DEN alone group (9 of 29 rats, 31%), the difference being statistically significant (P less than 0.05). No carcinogenic activity of dipyrone was demonstrated in the groups given 0.4% dipyrone for 72 weeks or 0.4% dipyrone for 25 weeks, followed by 0.05% phenobarbital (PB) for 50 weeks. However, glutathione S-transferase P positive (GST-P+) preneoplastic hepatic foci in these groups were observed at a higher incidence than in the untreated control group (P less than 0.01). (ii) Effect of dipyrone A and dipyrone B on induction of DEN-initiated GST-P+ hepatic foci in a medium-term bioassay system: 0.4% dipyrone A in drinking water and 0.57% dipyrone A or dipyrone B in powdered diet after DEN initiation had similar enhancing effects on the development of GST-P+ foci (P less than 0.001). (iii) The Ames mutation test in Salmonella: both dipyrone A and dipyrone B proved weakly mutagenic for strain TA100 in the presence or absence of S9 fraction.

4,4-Diphenyl-N-isopropyl-cyclohexylamine-hydrochloride (pramiverine, Sistalgin) was investigated alone and in combination (1 + 1000) with N-methyl-N-(2,3-dimethyl-5-oxo-1-phenyl-3-pyrazolin-4-yl)-aminomethanesulfonate (metamizole) in various species for acute toxicity after oral and intravenous administration, for local tolerance and subacute toxicity. In addition, long-term trials and reproduction toxicity studies were performed with pramiverine. Pramiverine was only slightly toxic and was well tolerated locally as an ampoule solution also in combination with metamizole. The acute trials of the two compounds in mice and rats like the subacute study in rats showed that the toxicity of metamizole was not increased by pramiverine. Rats tolerated in the long-term trial all pramiverine doses examined (0.5; 5.0; 50.0 mg/kg), while cholinolytic concomitant effects were observed in dogs under higher doses (5.0 and 20.0 mg/kg). Pramiverine did not have a foetotoxic and teratogenic effect in mice, rats and rabbits. In the perinatal and postnatal experiment in rats no effect on foetal development, viability and growth of the offspring as well as the course of labour and lactation ability of the dams was observed.

Mutagenic activity of the drugs analgine and aminophenazone was tested in the intraperitoneal and intrasanguine host-mediated assay after oral application together with equimolar doses of sodium nitrite. Salmonella typhimurium strain G46 was used as genetic indicator system; mice served as host animals for the bacteria. Analgine was found to be weakly mutagenic in the dose 2 mM/kg together with nitrite, aminophenazone was a strong mutagen in combination with nitrite in the doses 2 mM/kg and 0.2 mM/kg using the intrasanguine test with 1 h incubation of bacteria in the liver. In the intraperitoneal variant with 3 h incubation time of bacteria only aminophenazone was slightly mutagenic at the highest dose tested, 2 mM/kg. The relative nitrosation rate for aminophenazone was calculated by means of regression lines for mutagenic activity of dimethylnitrosamine and was found to be in the range of 2% in both systems for a dose of 2 mM/kg precursors.

The fact that aminopyrine is readily nitrosated and that the nitrosation product, dimethylnitrosamine, is potentially carcinogenic has led to the drug being withdrawn from therapeutic use. In the case of the other analgesics, nitrosation is not of any importance, neither in toxicological nor quantitative terms. The characteristic features of the metabolic pathways of phenacetin, paracetamol, and aspirin can occasionally entail toxicological consequences, such as methaemoglobin formation, liver damage, and long presence in the body, respectively. The prolonged and continuous administration of any of the three classes of drugs is not without risk. Adverse reactions of the allergic type cannot be detected by animal experiments.

A carcinogenicity study with dipyrone (metamizol methanesulfonate) was conducted in male and female Wistar rats. The compound was administered with the feed for a period of 24 months in doses of 0, 1000, or 3000 ppm, followed by a 6-month recovery period (without compound administration). The rats in the high-dose group, especially the females, showed a statistically significant body weight gain retardation which was not correlated with reduced feed consumption. The chronic administration of dipyrone did not influence the survival of the rats. No treatment-related changes in clinical signs and hematological parameters occurred. The absolute and relative weights of thyroids and pituitaries in the high-dose males were increased statistically significantly but were still within the normal range of the rat strain used. Histological examination of the animals which died intercurrently or were killed in extremis or at the end of the recovery period did not reveal any nonneoplastic or neoplastic changes which were compound related under the test conditions used. All of the tumors in all groups of animals were considered spontaneous in nature. Dipyrone did not show carcinogenic potential in rats in this study.

Analgin given repeatedly per os in dose 15 mg/kg to white male rats, causes changes in some indices of the liver NADPH-dependent mono-oxygenase system. At the end of the first month a decrease in the quantity of the microsomal protein was established as well as increase of the cytochrome's content P-450 and b5. The frequencies of cytochrome P-450-dependent biotransformations of substrates aminopyrine and aniline are also of different directions. At the end of the sixth month, because of multiple drug application all these indices are in the limits of the control values. A change in the catalytic features of cytochrome P-450, is established, which is expressed mainly by strongly decreased affinity to the substrates of first type. The Michaelis's constant Km for substrate aminopyrine depends on the duration of analgin introduction and increases up to 300% towards the control at the end of the sixth month.