A coupled Bio-EF process for mineralization of the pharmaceuticals furosemide and ranitidine: Feasibility assessment

A coupled Bio-EF treatment has been applied as a reliable process for the degradation of the pharmaceuticals furosemide (FRSM) and ranitidine (RNTD) in aqueous medium, in order to reduce the high energy consumption related to electrochemical technology. In the first stage of this study, electrochemical degradation of the drugs was assessed by the electro-Fenton process (EF) using a BDD/carbon-felt cell. Biodegradability of the drugs solutions was enhanced reaching BOD5/COD ratios close to the biodegradability threshold of 0.4, evidencing the formation of bio-compatible by-products (mainly short-chain carboxylic acids) which are suitable for biological post-treatment. Moreover, toxicity evaluation by the Microtox(®) method revealed that EF pre-treatment was able of detoxifying both, FRSM and RNTD solutions, constituting another indicator of biodegradability of EF treated solutions. In the second stage, electrolyzed solutions were treated by means of an aerobic biological process. A significant part of the short-chain carboxylic acids formed during the electrochemical phase was satisfactorily removed by the used selected microorganisms. The results obtained demonstrate the efficiency and feasibility of the integrated Bio-EF process.

Electrochemical advanced oxidation for cold incineration of the pharmaceutical ranitidine: mineralization pathway and toxicity evolution

Ranitidine (RNTD) is a widely prescribed histamine H2-receptor antagonist whose unambiguous presence in water sources appointed it as an emerging pollutant. Here, the degradation of 0.1 mM of this drug in aqueous medium was studied by electrochemical advanced oxidation processes (EAOPs) like anodic oxidation with electrogenerated H2O2 and electro-Fenton using Pt/carbon-felt, BDD/carbon-felt and DSA-Ti/RuO2–IrO2/carbon-felt cells. The higher oxidation power of the electro-Fenton process using a BDD anode was demonstrated. The oxidative degradation of RNTD by the electrochemically generated OH radicals obeyed a pseudo-first order kinetics. The absolute rate constant for its hydroxylation reaction was 3.39 × 109 M−1 s−1 as determined by the competition kinetics method. Almost complete mineralization of the RNTN solution was reached by using a BDD anode in both anodic oxidation with electrogenerated H2O2 and electro-Fenton processes. Up to 11 cyclic intermediates with furan moiety were detected from the degradation of RNTD, which were afterwards oxidized to short-chain carboxylic acids before their mineralization to CO2 and inorganic ions such as NH4+, NO3− and SO42−. Based on identified products, a plausible reaction pathway was proposed for RNTD mineralization. Toxicity assessment by the Microtox® method revealed that some cyclic intermediates are more toxic than the parent molecule. Toxicity was quickly removed following the almost total mineralization of the treated solution. Overall results confirm the effectiveness of EAOPs for the efficient removal of RNTD and its oxidation by-products from water.

Uptake and effects of a mixture of widely used therapeutic drugs in Eruca sativa L. and Zea mays L. plants

Pharmaceutically active compounds (PACs) are continuously dispersed into the environment due to human and veterinary use, giving rise to their potential accumulation in edible plants. In this study, Eruca sativa L. and Zea mays L. were selected to determine the potential uptake and accumulation of eight different PACs (Salbutamol, Atenolol, Lincomycin, Cyclophosphamide, Carbamazepine, Bezafibrate, Ofloxacin and Ranitidine) designed for human use. To mimic environmental conditions, the plants were grown in pots and irrigated with water spiked with a mixture of PACs at concentrations found in Italian wastewaters and rivers. Moreover, 10× and 100× concentrations of these pharmaceuticals were also tested. The presence of the pharmaceuticals was tested in the edible parts of the plants, namely leaves for E. sativa and grains for Z. mays. Quantification was performed by liquid chromatography mass spectroscopy (LC/MS/MS). In the grains of 100× treated Z. mays, only atenolol, lincomycin and carbamazepine were above the limit of detection (LOD). At the same concentration in E. sativa plants the uptake of all PACs was >LOD. Lincomycin and oflaxacin were above the limit of quantitation in all conditions tested in E. sativa. The results suggest that uptake of some pharmaceuticals from the soil may indeed be a potential transport route to plants and that these environmental pollutants can reach different edible parts of the selected crops. Measurements of the concentrations of these pharmaceuticals in plant materials were used to model potential adult human exposure to these compounds. The results indicate that under the current experimental conditions, crops exposed to the selected pharmaceutical mixture would not have any negative effects on human health. Moreover, no significant differences in the growth of E. sativa or Z. mays plants irrigated with PAC-spiked vs. non-spiked water were observed.

Biodegradability and ecotoxicitiy of tramadol, ranitidine, and their photoderivatives in the aquatic environment

PURPOSE

This study was designed to assess the fate and the overall potential impacts of the widely prescribed drugs ranitidine and tramadol after their introduction into the aquatic environment.

METHODS

The probability to detect these two drugs in the aquatic environment was studied by analyzing their abiotic and biotic degradation properties. For this purpose, samples were irradiated with different light sources, and three widely used biodegradability tests from the OECD series, the closed bottle test (OECD 301 D), the manometric respirometry test (OECD 301 F) and the Zahn-Wellens test (OECD 302 B), were conducted. The ecotoxicity of the photolytically formed transformation products was assessed by performing the bacterial growth inhibition test (EN ISO 10712). Furthermore, quantitative structure-activity relationship analysis and a risk analysis based on the calculation of the predicted environmental concentrations have also been conducted to assess the environmental risk potential of the transformation products. The possible formation of stable products by microbial or photolytical transformation has been investigated with DOC and LC-MS analytics.

RESULTS

In the present study, neither ranitidine, nor tramadol, nor their photoderivatives were found to be readily or inherently biodegradable according to test guidelines. The photolytic transformation was faster under a UV lamp compared to the reaction under an Xe lamp with a spectrum that mimics sunlight. No chronic toxicity against bacteria was found for ranitidine or its photolytic decomposition products, but a low toxicity was detected for the resulting mixture of the photolytic transformation products of tramadol.

CONCLUSIONS

The study demonstrates that transformation products may have a higher environmental risk potential than the respective parent compounds.

Effects of ranitidine and its photoderivatives in the aquatic environment

This study was designed to assess the overall ecotoxicity of ranitidine, a histamine H(2)-receptor antagonist that inhibits stomach acid production. Hence, in addition to ranitidine, its main two photoderivatives, obtained by solar simulator irradiation in water, were investigated. The photoproducts were identified by their physical features. Bioassays were performed on rotifers and microcrustaceans to assess acute and chronic toxicity, while SOS Chromotest and Ames test were utilized to detect the genotoxic potential of the investigated compounds. The results showed that ranitidine did not show any acute toxicity at the highest concentration tested (100 mg/L) for all the organisms utilized in the bioassays. Chronic exposure to these compounds caused inhibition of growth population on rotifers and crustaceans. Genotoxic and mutagenic effects were especially found for one photoproduct suggesting that transformation products, as frequently demonstrated, may show effects higher than the respective parental compound.

Metabonomic evaluation of idiosyncrasy-like liver injury in rats cotreated with ranitidine and lipopolysaccharide

Idiosyncratic liver injury occurs in a small fraction of people on certain drug regimens. The cause of idiosyncratic hepatotoxicity is not known; however, it has been proposed that environmental factors such as concurrent inflammation initiated by bacterial lipopolysaccharide (LPS) increase an individual's susceptibility to drug toxicity. Ranitidine (RAN), a histamine-2 receptor antagonist, causes idiosyncratic liver injury in humans. In a previous report, idiosyncrasy-like liver toxicity was created in rats by cotreating them with LPS and RAN. In the present study, the ability of metabonomic techniques to distinguish animals cotreated with LPS and RAN from those treated with each agent individually was investigated. Rats were treated with LPS or its vehicle and with RAN or its vehicle, and urine was collected for nuclear magnetic resonance (NMR)- and mass spectroscopy-based metabonomic analyses. Blood and liver samples were also collected to compare metabonomic results with clinical chemistry and histopathology. NMR metabonomic analysis indicated changes in the pattern of metabolites consistent with liver damage that occurred only in the LPS/RAN cotreated group. Principal component analysis of urine spectra by either NMR or mass spectroscopy produced a clear separation of the rats treated with LPS/RAN from the other three groups. Clinical chemistry (serum alanine aminotransferase and aspartate aminotransferase activities) and histopathology corroborated these results. These findings support the potential use of a noninvasive metabonomic approach to identify drug candidates with potential to cause idiosyncratic liver toxicity with inflammagen coexposure.

Unique gene expression and hepatocellular injury in the lipopolysaccharide-ranitidine drug idiosyncrasy rat model: comparison with famotidine

Rats cotreated with lipopolysaccharide (LPS) and ranitidine (RAN) but not LPS and famotidine (FAM) develop hepatocellular injury in an animal model of idiosyncratic drug reactions. Evaluation of liver gene expression in rats given LPS and/or RAN led to confirmation that the hemostatic system, hypoxia, and neutrophils (PMNs) are critical mediators in LPS/RAN-induced liver injury. We tested the hypothesis that unique gene expression changes distinguish LPS/RAN-treated rats from rats given LPS or RAN alone and from those cotreated with LPS/FAM. Rats were treated with a nonhepatotoxic dose of LPS (44.4 x 10(6) endotoxin units/kg, iv) or its vehicle. Two hours thereafter they were given RAN (30 mg/kg, iv), FAM (either 6 mg/kg, a pharmacologically equi-efficacious dose, or 28.8 mg/kg, an equimolar dose, iv), or vehicle. They were killed 2 or 6 h after drug treatment for evaluation of hepatotoxicity (2 and 6 h) and liver gene expression (2 h only). At a time before the onset of hepatocellular injury, hierarchical clustering distinguished rats treated with LPS/RAN from those given LPS alone. 205 probesets were expressed differentially to a greater or lesser degree only in LPS/RAN-treated rats compared to LPS/FAM or LPS alone, which did not develop liver injury. These included VEGF, EGLN3, MAPKAPK-2, BNIP3, MIP-2, COX-2, EGR-1, PAI-1, IFN-gamma, and IL-6. Expression of these genes was confirmed by real-time PCR. Serum concentrations of MIP-2, PAI-1, IFN-gamma, and IL-6 correlated with their respective gene expression patterns. Overall, the expression of several gene products capable of controlling requisite mediators of injury (i.e., hemostasis, hypoxia, PMNs) in this model were enhanced in livers of LPS/RAN-treated rats. Furthermore, enhanced expression of MAPKAPK-2 in RAN-treated rats and its target genes in LPS/RAN-treated rats suggests that p38/MAPKAPK-2 signaling is a regulation point for enhancement of LPS-induced gene expression by RAN.

Biodegradability and toxicity of pharmaceuticals in biological wastewater treatment plants

In this experimental study both biological treatability of pharmaceuticals and their potential toxic effect in biological processes were evaluated. The pharmaceuticals were selected among those that are present at higher concentration in the Italian wastewater treatment plant effluents and widely used as antiulcer (ranitidine), beta-blocker (atenolol) and antibiotic (lincomycin). The present paper is the continuation of a work already presented,[1] which used a synthetic wastewater fed to laboratory scale SBR (Sequencing Batch Reactor) operated with different sludge ages (8 and 14 days), different biochemical conditions (aerobic or anoxic-aerobic mode) and several influent drug concentrations (2, 3 and 5 mg/L). In this case a real municipal wastewater was used as influent to the SBR. In parallel, batch tests were conducted to determine the removal kinetics of drugs and nitrogen. Toxicity tests using a titrimetric biosensor to verify possible inhibition on microorganisms were also performed. Finally, the possible adsorption of the pharmaceuticals on activated sludge was evaluated. The drugs under investigation showed different behaviours in terms of both biodegradability and toxicity effect on nitrifiers. Ranitidine showed generally low removal efficiencies (17-26%) and a chronic inhibition on nitrification. Atenolol showed generally higher removal efficiencies than ranitidine, even if the fairly good efficiency obtained in the previous experimentation with synthetic wastewater (up to 90%) was not attained with real wastewater (36%). No inhibition on nitrification was observed on both acclimated and non acclimated microorganisms with a high nitrification activity, whilst it was present with activated sludge characterised by a lower nitrification activity. Consistently with his pharmaceutical properties, lincomycin showed significant inhibition on nitrification activity.

Biochemical and histological studies on H2-receptor antagonist ranitidine-induced hepatotoxicity in rats

This study was designed to investigate the hepatotoxicity of ranitidine treatment in dose levels of 10, 30, and 50 mg/kg b.wt. for 3 weeks period in male rats. The results showed some adverse changes in rats treated with either 10 or 30 mg/kg. Treatment with dose of 50 mg/kg produced marked increase in the activity of both acid phosphatase in liver and aspartate aminotransferase in serum and liver, with a tendency for increase in serum alanine aminotransferase activity. Also, a significant decrease in the serum activity of both amylase and alkaline phosphatase was noted. Microscopic examination of livers of the same animals revealed absence of some hepatic cells, pyknotic nuclei, dilatation of blood sinusoids, binucleated cells, and infiltration of lymphocytes. These biochemical and histological changes indicate that ranitidine when given chronically in high dose could produce hepatotoxicity in rats.

Coagulation-Mediated Hypoxia and Neutrophil-Dependent Hepatic Injury in Rats Given Lipopolysaccharide and Ranitidine

Idiosyncrasy-like liver injury occurs in rats cotreated with nonhepatotoxic doses of ranitidine (RAN) and bacterial lipopolysaccharide (LPS). Hepatocellular oncotic necrosis is accompanied by neutrophil (PMN) accumulation and fibrin deposition in LPS/RAN-treated rats, but the contribution of PMNs to injury has not been shown. We tested the hypothesis that PMNs are critical mediators of LPS/RAN-induced liver injury and explored the potential for interaction between PMNs and hemostasis-induced hypoxia. Rats were given either LPS (44.4 x 10(6) endotoxin units/kg) or its vehicle and then RAN (30 mg/kg) or its vehicle 2 h later. They were killed 3 or 6 h after RAN treatment, and hepatocellular injury was estimated from serum alanine aminotransferase activity and liver histopathology. Plasma PMN chemokine concentration and the number of PMNs in liver increased after LPS treatment at 3 h and were not markedly altered by RAN cotreatment. Depletion of circulating PMNs attenuated hepatic PMN accumulation and liver injury and had no effect on coagulation system activation. Anticoagulation with heparin attenuated liver fibrin deposition and injury in LPS/RAN-treated rats; however, heparin had little effect on liver PMN accumulation or plasma chemokine concentration. Liver hypoxia occurred in LPS/RAN-cotreated rats and was significantly reduced by heparin. In vitro, hypoxia enhanced the killing of rat hepatocytes by PMN elastase and shortened its onset, indicating a synergistic interaction between PMNs and hypoxia. The results suggest that PMNs are involved in the hepatocellular injury caused by LPS/RAN-cotreatment and that hemostasis increases sensitivity to PMN-induced hepatocellular injury by causing liver hypoxia.

Role of hepatic fibrin in idiosyncrasy-like liver injury from lipopolysaccharide-ranitidine coexposure in rats

Coadministration of nonhepatotoxic doses of the histamine 2-receptor antagonist ranitidine (RAN) and bacterial lipopolysaccharide (LPS) results in hepatocellular injury in rats, the onset of which occurs in 3 to 6 hours. This reaction resembles RAN idiosyncratic hepatotoxicity in humans. Early fibrin deposition occurs in livers of rats cotreated with LPS/RAN. Accordingly, we tested the hypothesis that the hemostatic system contributes to liver injury in LPS/RAN-treated rats. Rats were given either LPS (44.4 x 10(6) EU/kg) or its vehicle, then RAN (30 mg/kg) or its vehicle 2 hours later. They were killed 2, 3, 6, 12, or 24 hours after RAN treatment, and liver injury was estimated from serum alanine aminotransferase activity. A modest elevation in serum hyaluronic acid, which was most pronounced in LPS/RAN-cotreated rats, suggested altered sinusoidal endothelial cell function. A decrease in plasma fibrinogen and increases in thrombin-antithrombin dimers and in serum concentration of plasminogen activator inhibitor-1 occurred before the onset of liver injury. Hepatic fibrin deposition was observed in livers from LPS/RAN-cotreated rats 3 and 6 hours after RAN. Liver injury was abolished by the anticoagulant heparin and was significantly attenuated by the fibrinolytic agent streptokinase. Hypoxia, one potential consequence of sinusoidal fibrin deposition, was observed in livers of LPS/RAN-treated rats. In conclusion, the results suggest that the hemostatic system is activated after LPS/RAN cotreatment and that fibrin deposition in liver is important for the genesis of hepatic parenchymal cell injury in this model.

Gene Expression Analysis Points to Hemostasis in Livers of Rats Cotreated with Lipopolysaccharide and Ranitidine

Studies in rats have demonstrated that modest underlying inflammation can precipitate idiosyncratic-like liver injury from the histamine 2-receptor antagonist, ranitidine (RAN). Coadministration to rats of nonhepatotoxic doses of RAN and the inflammagen, bacterial lipopolysaccharide (LPS), results in hepatocellular injury. We tested the hypothesis that hepatic gene expression changes could be distinguished among vehicle-, LPS-, RAN- and LPS/RAN-treated rats before the onset of significant liver injury in the LPS/RAN-treated rats (i.e., 3 h post-treatment). Rats were treated with LPS (44 x 10(6) EU/kg, i.v.) or its vehicle, then two hours later with RAN (30 mg/kg, i.v.) or its vehicle. They were killed 3 h after RAN treatment, and liver samples were taken for evaluation of liver injury and RNA isolation. Hepatic parenchymal cell injury, as estimated by increases in serum alanine aminotransferase (ALT) activity, was not significant at this time. Hierarchal clustering of gene expression data from Affymetrix U34A rat genome array grouped animals according to treatment. Relative to treatment with vehicle alone, treatment with RAN and/or LPS altered hepatic expression of numerous genes, including ones encoding products involved in inflammation, hypoxia, and cell death. Some were enhanced synergistically by LPS/RAN cotreatment. Real-time PCR confirmed robust changes in expression of B-cell translocation gene 2, early growth response-1, and plasminogen-activator inhibitor-1 (PAI-1) in cotreated rats. The increase in PAI-1 mRNA was reflected in an increase in serum PAI-1 protein concentration in LPS/RAN-treated rats. Consistent with the antifibrinolytic activity of PAI-1, significant fibrin deposition occurred only in livers of LPS/RAN-treated rats. The results suggest the possibility that expression of PAI-1 promotes fibrin deposition in liver sinusoids of LPS/RAN-treated rats and are consistent with the development of local ischemia and consequent tissue hypoxia.

Application of high-throughput Fourier-transform infrared spectroscopy in toxicology studies: contribution to a study on the development of an animal model for idiosyncratic toxicity

An evaluation of high-throughput Fourier-transform infrared spectroscopy (FT-IR) as a technology that could support a "metabonomics" component in toxicological studies of drug candidates is presented. The hypothesis tested in this study was that FT-IR had sufficient resolving power to discriminate between urine collected from control rat populations and rats subjected to treatment with a potent inflammatory agent, bacterial lipopolysaccharide (LPS). It was also hypothesized that co-administration of LPS with ranitidine, a drug associated with reports of idiosyncratic susceptibility, would induce hepatotoxicity in rats and that this could be detected non-invasively by an FT-IR-based metabonomics approach. The co-administration of LPS with "idiosyncratic" drugs represents an attempt to develop a predictive model of idiosyncratic toxicity and FT-IR is used herein to support characterization of this model. FT-IR spectra are high dimensional and the use of genetic programming to identify spectral sub-regions that most contribute to discrimination is demonstrated. FT-IR is rapid, reagentless, highly reproducible and inexpensive. Results from this pilot study indicate it could be extended to routine applications in toxicology and to supporting characterization of a new animal model for idiosyncratic susceptibility.

Ranitidine treatment during a modest inflammatory response precipitates idiosyncrasy-like liver injury in rats

Drug idiosyncrasy is an adverse event of unknown etiology that occurs in a small fraction of people taking a drug. Some idiosyncratic drug reactions may occur from episodic decreases in the threshold for drug hepatotoxicity. Previous studies in rats have shown that modest underlying inflammation triggered by bacterial lipopolysaccharide (LPS) can decrease the threshold for xenobiotic hepatotoxicity. The histamine-2 (H2)-receptor antagonist ranitidine (RAN) causes idiosyncratic reactions in people, with liver as a usual target. We tested the hypothesis that RAN could be rendered hepatotoxic in animals undergoing a modest inflammatory response. Male rats were treated with a nonhepatotoxic dose of LPS (44 x 10(6) endotoxin units/kg i.v.) or its vehicle and then 2 h later with a nonhepatotoxic dose of RAN (30 mg/kg i.v.) or its vehicle. Liver injury was evident only in animals treated with both RAN and LPS as estimated by increases in serum alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transferase activities within 6 h after RAN administration. LPS/RAN cotreatment resulted in midzonal liver lesions characterized by acute necrosuppurative hepatitis. Famotidine (FAM) is an H2-antagonist for which the propensity for idiosyncratic reactions is far less than RAN. Rats given LPS and FAM at a dose pharmacologically equipotent to that of RAN did not develop liver injury. In vitro, RAN sensitized hepatocytes to killing by cytotoxic products from activated neutrophils, whereas FAM lacked this ability. The results indicate that a response resembling human RAN idiosyncrasy can be reproduced in animals by RAN exposure during modest inflammation.

Effects of substances affecting protein kinase C on histamine-evoked stimulation of cyclic AMP formation in chick cerebral cortex

In membrane preparation of chick cerebral cortex, HA (histamine) did not affect both basal and forskolin-stimulated adenylyl cyclase activity. However, in slices of chick cerebral cortex prelabeled with [3H]adenine, HA, as well as 2-methylHA, 4-methylHA, and N alpha-methylHA, potently increased [3H]cyclic AMP accumulation in a concentration-dependent manner. The stimulatory effect of the HA-ergic compounds on cyclic AMP formation was antagonized by HA H2-receptor blockers (aminopotentidine, ranitidine), and by chelerythrine (50 microM), a potent and selective inhibitor of PKC (protein kinase C). Of the two other tested PKC inhibitors H-7 (100 microM) significantly reduced the HA action, while the effect of staurosporine (1 microM) did not reach the level of statistical significance. Preincubation of chick cerebral cortical slices with a PKC activator, PDB (4 beta-phorbol 12,13-dibutyrate, 1 microM), markedly enhanced the accumulation of cyclic AMP evoked by HA, 2-methylHA, 4-methylHA and N alpha-methylHA. 4 beta-Phorbol, inactive on PKC, was ineffective. A possible role of PKC in the regulation of HA-induced cyclic AMP synthesis in chick cerebrum has been discussed.

Neurotoxic convulsions induced by histamine H2 receptor antagonists in mice

Convulsive potency was evaluated to investigate the mechanism of neurotoxic convulsion induced by histamine H2 receptor antagonists (H2 blockers). Four H2 blockers, cimetidine (721-1236 nmol), ranitidine (477-954 nmol), famotidine (7.4-44 nmol), and nizatidine (226-603 nmol) were administered intracerebrally (i.c.) to mice. Dose dependency of clonic and/or tonic convulsion was observed, and the ED50 values of convulsive occurrence for cimetidine, ranitidine, famotidine, and nizatidine were 997, 662, 23.4, and 404 nmol, respectively. Intraperitoneal pretreatment of muscimol, aminooxy acetic acid, diazepam, (+/-)2-amino-7-phosphonoheptanoic acid (APH), or (+)MK801 suppressed the tonic convulsion after i.c. administration of ranitidine, but had no effect on clonic convulsion. Furthermore, the convulsive threshold concentration in the brain determined by constant rate infusion of ranitidine was not affected by the pretreatment of muscimol, diazepam, APH, and MK801. Ed50 values for convulsive occurrence after i.c. administration of four H2 blockers correlated well with the EC50 values for gastric acid secretion inhibition. The convulsive threshold concentrations of cimetidine and ranitidine in the brain were 11 and 2.5 microM, respectively, which were similar to the dissociation constants determined from the inhibition of gastric acid output in mice. From these results, tonic convulsion induced by H2 blockers can be suppressed by GABAergic or glutamatergic anticonvulsants, while clonic convulsion induced by H2 blockers may be associated with the blockade of H2 receptor in the brain and not be directly associated with the GABA and glutamate-mediated neurotransmission.

Effect of renal failure on neurotoxicity of ranitidine in rats

We investigated the effect of acute renal failure on the neurotoxicity of ranitidine in rats. Experimental acute renal failure was produced by bilateral ureteral ligation. Ranitidine was infused into the ureter ligated (UL) and control rats at the rate of 3.25 mg/min through the jugular vein until the onset of clonic convulsion. In UL rats, the onset time of convulsion was shorter and ranitidine concentrations in plasma and cerebrospinal fluid (CSF) were lower than those of control rats. However, the ranitidine concentration in the brain at the onset of convulsion was not different between the UL and control rats. From these findings, we concluded that acute renal failure is one of the risk factors for ranitidine neurotoxicity, and the increased sensitivity to the drug on the central nervous system may contribute to the increased toxicity of ranitidine in renal failure.

Effect of renal or hepatic dysfunction on neurotoxic convulsion induced by ranitidine in mice

We investigated the effect of acute renal and hepatic dysfunction on the neurotoxicity of ranitidine, a histamine H2 receptor antagonist. Experimental acute hepatic and renal dysfunction in mice were produced by i.p. injection of uranyl nitrate (UN) and carbon tetrachloride (CT), respectively. Ranitidine was then constantly infused into the tail vein until the onset of clonic convulsion. When compared to control mice, UN treated mice had a significantly shorter onset time to clonic convulsion, lower total dose and higher plasma concentration at initiation of clonic convulsion. In contrast, the convulsive threshold concentration in the brain of UN treated mice was not significantly different from that of control mice. In CT treated mice, all pharmacokinetic and pharmacodynamic data described above were not significantly different from those of the control mice. No significant difference in the brain/plasma concentration ratio was observed between both disease models and the corresponding control mice. Finally, the effect of UN and CT treatment on the convulsive potency after intracerebral (i.c.) administration of ranitidine was investigated in mice. Potentiation of the intrinsic neurotoxic sensitivity to ranitidine could not be demonstrated for mice with renal or hepatic dysfunction. From these findings, we conclude that renal dysfunction is a risk factor for ranitidine neurotoxicity, and this increased risk results from increase in the drug concentration in plasma and brain as a result of impaired renal excretion. No apparent effect of acute hepatic dysfunction was observed on both the pharmacokinetic and pharmacodynamic behavior of the drug.

An evaluation of the safety of ranitidine during seven years daily oral administration to beagle dogs

1. Ranitidine hydrochloride was administered orally to Beagles at doses equivalent to 50 mg once daily, or 5 mg twice daily, of ranitidine base/kg for more than 7 years. 2. Apart from looseness of faeces, seen mainly after doses of 50 mg/kg and only rarely after the first year of such treatment, there were no adverse clinical effects. There were no deaths related to treatment. 3. Periodic gastroscopy revealed nothing abnormal. 4. Peak plasma levels of ranitidine occurred within 2 h of dosing; levels were proportional to the doses administered. 5. There were no major differences in fasting plasma gastrin levels between treated and untreated dogs; the expected increase occurred in response to the provision of food and, predictably, this was greater following a dose of ranitidine. 6. A normal histamine-induced gastric secretory response was demonstrated. 7. Necropsy revealed no lesions of toxicological significance. Macroscopically the stomachs appeared normal but microscopic examination showed some gastritis in both treated and control dogs. No changes in enterochromaffin-like (ECL) cells were detected. Electron microscopy showed unimpaired secretory activity of parietal cells. 8. Thus, after more than 7 years administration to beagle dogs of doses in excess of the normal daily therapeutic dose, the stomachs showed no changes attributable to treatment and their secretory capacity was unimpaired.

Oxmetidine (H2 receptor antagonist) induced cytotoxicity in isolated rat hepatocytes

Oxmetidine, a new and more potent analogue of the H2 receptor antagonist, cimetidine, was recently withdrawn from clinical trials because of associated hepatotoxicity. We investigated the potential hepatotoxicity of the drug in vitro and in vivo in the rat. In addition, we investigated, in in vitro experiments, the potential hepatoxicity of other gastric acid inhibitory drugs (cimetidine, ranitidine, omeprazole and nolinium bromide). In in vitro experiments, oxmetidine, at various concentrations, was added to isolated hepatocyte incubations and cytotoxicity was assayed by trypan blue exclusion. In in vivo experiments, oxmetidine was administered both i.p. and orally, and hepatotoxicity was assessed by serum biochemical measures (transaminases, alkaline phosphatase, 5' nucleotidase, gamma glutamyl transpeptidase) and liver histopathology. In the in vitro studies, the addition of oxmetidine to the hepatocyte incubations was associated with significant (P less than 0.001) dose and time dependent cytotoxicity. However, the in vivo experiments revealed no significant changes in serum biochemistry and no significant alterations in liver histopathology up to 72 h following the administration three different dosages of oxmetidine. Of the other gastric acid inhibitory drugs, only nolinium bromide was associated with significant (P less than 0.001) in vitro cytotoxicity. Our in vitro observations establish that oxmetidine is cytotoxic to isolated rat hepatocytes and suggest that nolinium bromide be further evaluated for potential hepatotoxicity.

Effects of three H2 antagonists on the isolated perfused rat liver. Correlation of bile flow changes with potential for causing hepatic disease in patients

The adverse effects of oxmetidine, an H2 blocking agent which has been shown to produce hepatic injury in 1-4% of patients, on an in vitro model were compared with those of cimetidine and ranitidine which have led to only rare instances of hepatic injury. Bile flow was measured in the isolated perfused rat liver (Wistar rats), comparing the effects of each of the three drugs with control perfusions. Oxmetidine in concentrations of 3 X 10(-3) M or greater led to a decrease in bile flow within 15 min and, at a concentration of 5 X 10(-3) M, to complete cessation of flow within 5 min. Lower concentrations (5 X 10(-4) M) led to a marked choleresis. Ranitidine and cimetidine in concentrations up to 5 X 10(-3) M produced no decrease in bile flow. Ranitidine, however, led to a choleresis at a concentration of 5 X 10(-3) M. The positive correlation between in vivo and in vitro toxicity supports the view that in vitro testing may prove to be of use in predicting the hepatotoxic potential of a drug.

Effects of H2-blocking agents on hepatocytes in vitro: correlation with potential for causing hepatic disease in patients

The adverse effects on an in vitro model of oxmetidine, an H2-blocking agent which has been shown to produce hepatic injury in 1 to 4% of patients, were compared with those of cimetidine and ranitidine which have led to only rare instances of hepatic injury. Suspensions of hepatocytes, freshly isolated from Sprague-Dawley rats, were exposed to the three drugs. Oxmetidine, in concentrations of 3 X 10(-3) M or greater, led to leakage of AST into the medium after 4 hr of incubation. Ranitidine and cimetidine, in concentrations up to 5 X 10(-3) M, produced no identifiable leakage. Pretreatment of rats with phenobarbital, 3-methylcholanthrene, or SKF 525A resulted in no significant enhancement or inhibition of the oxmetidine effects. These results suggest that the adverse effects of oxmetidine on the hepatocytes are produced by the native compound, not a metabolite. The positive correlation between in vivo and in vitro toxicity supports the view that in vitro testing may prove to be of use in predicting the hepatotoxic potential of a drug.

Ranitidine as an inhibitor of liver regeneration

The effects of ranitidine, a new H2-receptor antagonist, on liver regeneration were investigated using a protocol described previously. The animals in Group I had standard two-thirds hepatectomy. In Group II, the rats received an 8 mg/kg intramuscular dose of ranitidine immediately and 24 and 48 hours after two-thirds hepatectomy. In Group III, the rats had the same amounts of ranitidine after a sham operation. Mortality rate, liver weight restoration, mitotic activities of the residual livers, and serum levels of aminotransferases were examined from 24 hours to 14 days after operation. The mortality was very high in Group II (45 percent), whereas no rats died in Group I, and only 1 of 35 animals died in Group III. Administration of ranitidine after hepatectomy resulted in suppression not only of liver restoration, but also of the mitotic activities of hepatocytes. The serum aminotransferase levels in Group II had a tendency to increase after hepatectomy, compared with the levels in Group I. Using light microscopy, we detected that the hepatectomized group treated with ranitidine (Group II) underwent profound liver steatosis and marked dilatation of sinusoidal spaces. The present and previous observations by us indicate that ranitidine also inhibits, like cimetidine, liver regeneration after hepatectomy. The causes of the inhibitory effects of both cimetidine and ranitidine on hepatocyte cell division have also been discussed herein.

Pre- and neonatal exposure to cimetidine but not ranitidine adversely affects adult sexual functioning of male rats

Cimetidine, ranitidine or water were administered to pregnant rats from the 12th day of pregnancy through weaning at 21 days of age. The effects of such treatments upon the male progeny were evaluated. Anogenital distance and indices, measures of masculinity, were found to be reduced (p less than 0.05) in pups of cimetidine-exposed dams but not in the pups obtained from either the ranitidine or water controls. In addition, at 55 days and 110 days of age, the testes and ventral prostate-seminal vesicles (androgen responsive tissues) of the rats exposed to cimetidine were smaller (p less than 0.05) than those of the other two groups. Moreover, at both 55 and 110 days of age, the testosterone levels were reduced (p less than 0.05) in these same pups. Despite the fact that the cimetidine-exposed animals had reduced testosterone levels compared to the other two groups, the LH levels did not differ between the three groups. Finally, both before and after exogenous androgen replacement, the sexual behavior of the cimetidine exposed animals was diminished when compared to that of the other two groups. These results suggest that cimetidine but not ranitidine adversely affects male androgenization and neuroendocrine programming and suggests that its use in pregnant women may adversely affect the adult sexual behavior and development of their male progeny.

[Effects of intravenous administration of ranitidine hydrochloride on the fertility of the male and female rats]

The effects of ranitidine hydrochloride, a histamine H2-receptor antagonist, on the reproductivity of male and female rats of Crj:CD (SD) strain and the development of their fetuses were examined. Ranitidine hydrochloride was intravenously administered once daily at dose levels of 5, 15 and 40 mg/kg in base weight respectively, to males from 60 days before mating until the completion of mating, and to females from 14 days before mating up to day 7 of gestation. All pregnant females were killed on day 20 of gestation and their fetuses were examined morphologically. Tachypnea, prone position and transient tremor were observed for a short period of time directly after an intravenous administration of ranitidine in the dose of 40 mg/kg, which were probably induced by a rapid fall in blood pressure. There was a significant decrease in the weight of spleen in males of 15 and 40 mg/kg groups. Treatment with ranitidine hydrochloride did not have any influence on mating performances and pregnancy at all dose levels. In observation of the fetuses, there was no influence of ranitidine hydrochloride administration on fetal growth and development. A few external, skeletal and visceral malformations were seen sporadically in each group, and 19 cases of dwarf fetuses were observed in 2 dams of 40 mg/kg group, but these changes were not attributable to administration of the drug. These results indicated that ranitidine hydrochloride intravenously administered to males and females before mating and to pregnant females in early stages of gestation had no toxic effects on reproductivity in either sex at the dose of 40 mg/kg/day or less.

[Effects of intravenous administration of ranitidine hydrochloride to the female rat in perinatal and postnatal periods]

The effects of ranitidine hydrochloride, a histamine H2-receptor antagonist, on delivery, lactation, postnatal development of F1 generation of Crj:CD (SD) rats were examined. Ranitidine hydrochloride was intravenously administered once daily from day 17 of gestation to day 21 after delivery at dose levels of 5, 15 and 40 mg/kg in base weight respectively. All females were allowed to litter naturally, and postnatal development of offsprings was observed. Tachypnea, prone position and transient tremor were observed for approximately one minute directly after an intravenous administration of ranitidine in the dose of 40 mg/kg, which were probably induced by a rapid fall in blood pressure. In delivery and postpartum observation, there occurred no influence of the ranitidine administration on maternal body weight, delivery and lactation. In studies on general behavior of F1 rats, no abnormal changes were observed on postnatal development and various functions such as reflex response and learning. Ranitidine treatment did not affect reproductive performances of F1 generation. A slight inhibition in body weight gain and a slight decrease in average weight of liver were observed in F1 females of 40 mg/kg group, but no other influence attributable to the ranitidine administration was observed on the general state and development of offsprings. In necropsy of offsprings, hydronephrosis, transitional epithelial carcinoma, kinky tail, unilateral absence of testis and epididymis were observed in one case of ranitidine-treated groups. But they were not attributable to administration of ranitidine. In summary, it was concluded that ranitidine hydrochloride had no effects on delivery and lactation of dams, and also on viability, development and various functions of F1 generation at the dose of 40 mg/kg/day or less.

[Effects of intravenous administration of ranitidine hydrochloride to the pregnant rat in organogenesis period]

The effects of ranitidine hydrochloride, a histamine H2-receptor antagonist, on development and general behavior of F1 generation of Crj: CD (SD) rats were examined. Ranitidine hydrochloride was intravenously administered once daily from day 7 to 17 of gestation at dose levels of 5, 15 and 40 mg/kg in base weight respectively. Two-thirds of females were killed on day 20 of gestation to examine the development of fetuses, the remaining females were allowed to litter naturally and the postnatal development of the offsprings was observed. Tachypnea, prone position and transient tremor were observed for approximately 15 from 30 seconds directly after an intravenous administration of ranitidine hydrochloride in the dose of 40 mg/kg, which were probably induced by a rapid fall in blood pressure. During the gestation period, there occurred a slight depression of the maternal body weight gain in the ranitidine-treated groups. At the stage of lactation, the body weights of dams showed slightly lower levels than control and their liver weights of dams were also inclined to decrease in 15 and 40 mg/kg groups. In the observation of the fetuses, there were no significant differences between the control and ranitidine-treated groups concerning fetal growth and development, external, skeletal and internal anomalies in fetuses. In delivery and postpartum observation, no influence of ranitidine administration was observed on the litter size, mortality rate of F1 pups. There was a tendency towards decrease in body weight in males of the ranitidine-treated groups. But no significant changes were observed in general behavior, postnatal development, various functions such as reflex response, learning and reproductive performances of F1 generation. Therefore, it was concluded that ranitidine hydrochloride had no effects on fetal and postnatal development, general behavior and various functions of F1 generation at the dose of 40 mg/kg/day or less.

Studies with specific agonists and antagonists of the role of histamine H1- and H2-receptor activation in the pathogenesis of gastric lesions in rats

Although the factors involved in the induction of gastric pathology have long been studied, the exact roles of the two histamine receptors in this process are still obscure. The aim of this study was to evaluate the consequences of the activation of histamine H1- and/or H2-receptors in the pathogenesis of gastric damage and antagonism of these pathological developments by specific antagonists. The following agents were used: histamine as H1- and H2H2-agonist; 2-pyridylethylamine (PEA) and mepyramine as H1-agonist and antagonist; dimaprit and ranitidine as H2-agonist and antagonist. Intravenous administration of the agonists caused definite gastric damage in rats. Both the antagonists inhibited histamine-induced gastric lesions, but the PEA and dimaprit-induced erosions could be prevented only by giving the specific H1- or H2-antagonist. In conclusion, activation of either H1- or H2-receptors can play a crucial role in the pathogenesis of histamine-induced gastric damage in rats.

The effects of cimetidine and ranitidine on psychomotor function in healthy volunteers

Single oral doses of cimetidine (400 mg), ranitidine (150 mg), promethazine (25 mg) or placebo were administered to 8 healthy volunteers in a double-blind study. Cimetidine and ranitidine did not cause any significant change in critical flicker frequency (c.f.f.), reaction time, pursuit rotor of the visual analogue scale scores for sedation. Promethazine significantly lowered c.f.f., prolonged reaction time and increased sedation when compared with placebo. It is concluded that in this study cimetidine and ranitidine had little, if any, effect on psychomotor function.

The H2-antagonists, cimetidine and ranitidine: studies on performance

The effects of single oral doses of cimetidine (200 and 400 mg) and ranitidine (150 and 300 mg) were evaluated on visuo-motor coordination, dynamic visual acuity, digit symbol substitution, symbol copying, and critical flicker fusion, and on subjective assessments of mood and well-being in seven healthy female volunteers. The study was double blind and placebo controlled, and triprolidine (10 mg) was used as an active control. With cimetidine and ranitidine there were no adverse changes in performance, central nervous function or subjective assessment of mood. Triprolidine impaired visuo-motor coordination, reduced the number of substitutions on the digit symbol substitution test and the number of symbols copied, lowered the critical flicker fusion threshold and reduced dynamic visual acuity. Cimetidine (200-400 mg) and ranitidine (150-300 mg) are highly unlikely to impair performance, and may be used in individuals involved in skilled activity.

DNA damage induced by nitrosated ranitidine in cultured mammalian cells

Ranitidine, a new H-2 receptor antagonist more potent than cimetidine in inhibiting gastric secretion, reacted under acid conditions with a twofold molar amount of nitrite (a nitrite/ranitidine ratio about 1000 times that likely to occur in gastric juice of treated humans) yielding a nitroso derivative capable of inducing a dose-dependent DNA fragmentation in cultured Chinese hamster ovary cells.