Hepatic drug metabolizing enzyme induction and serum triacylglycerol elevation in rats treated with chlordiazepoxide, griseofulvin, rifampicin and phenytoin

The short-term toxicity and metabolome of Benzene

A 14-day rat study with plasma metabolomics was conducted to evaluate the toxicity of Benzene. Wistar rats were orally administered Benzene daily at doses of 0, 300 and 1000 mg/kg bw. The study identified liver and kidneys as target organs of Benzene toxicity and found reductions in total white blood cells, absolute lymphocyte and eosinophil cell counts, and increased relative monocyte counts suggesting bone marrow as a target organ. The study also confirmed liver as a target organ using metabolomics, which showed indications of a stress reaction in rats and changes in metabolites suggestive of a metabolic disorder. The metabolomics investigations did not find any other toxicologically relevant modes of action, and the observed metabolite changes were not associated with markers for mitochondrial dysfunction. The study concludes that integration of omics technologies, such as metabolomics, in regulatory toxicity studies is possible, confirms existing knowledge and adds additional information that can be used for mechanistic understanding of observed toxicity.

Alterations in morphology and hepatorenal indices in rats subacutely exposed to bitumen extract

Bitumen is a complex mixture of dense and extremely viscous organic liquids produced by distillation of crude oil during petroleum refining. Nigeria has a large deposit of natural bitumen, yet to be fully exploited. Discharges of petroleum hydrocarbons and other petroleum-derived products have caused environmental pollution and adverse human health effects in several oil-rich communities. In this study, bitumen obtained from a seepage source in Agbabu, the town of first discovery, was used in sub-acute toxicity studies in a rat experimental model, in order to assess potential health risks posed to local populace sequel to full exploitation of bitumen. Dosages were chosen to accommodate low to high cases of environmental exposures. Male Wistar rats were administered, per os, dosages of bitumen extract at 5, 3, 2, and 1 mg/kg body weight. Following euthanasia 28 days later, histological findings revealed severe portal congestion and cellular infiltration in the liver, while in the kidney there were protein casts in the tubular lumen. The relative liver and kidney weights in the 5 mg/kg groups were 34% and 40% higher than in the controls, with a concomitant decrease in food and water consumption. Furthermore, plasma clinical analyses revealed marked elevation in aspartate aminotransferase and triglycerides levels in bitumen extract-intoxicated rats. The results indicate the potential hepatorenal toxicity in adult rats following repeated exposure to bitumen extract.

Drug-Induced Liver Toxicity and Prevention by Herbal Antioxidants: An Overview

The liver is the center for drug and xenobiotic metabolism, which is influenced most with medication/xenobiotic-mediated toxic activity. Drug-induced hepatotoxicity is common and its actual frequency is hard to determine due to underreporting, difficulties in detection or diagnosis, and incomplete observation of exposure. The death rate is high, up to about 10% for drug-induced liver damage. Endorsed medications represented >50% of instances of intense liver failure in a study from the Acute Liver Failure Study Group of the patients admitted in 17 US healing facilities. Albeit different studies are accessible uncovering the mechanistic aspects of medication prompted hepatotoxicity, we are in the dilemma about the virtual story. The expanding prevalence and effectiveness of Ayurveda and natural products in the treatment of various disorders led the investigators to look into their potential in countering drug-induced liver toxicity. Several natural products have been reported to date to mitigate the drug-induced toxicity. The dietary nature and less adverse reactions of the natural products provide them an extra edge over other candidates of supplementary medication. In this paper, we have discussed the mechanism involved in drug-induced liver toxicity and the potential of herbal antioxidants as supplementary medication.

Possible Induction of Cholinesterase in Epileptic Patients Treated With Anticonvulsant Drugs: Relationship With Lipoprotein Levels

The effect of enzyme-inducing anticonvulsant drugs on the serum concentrations of lipoproteins has been widely studied. However, there is little agreement between the results with regard to the possible development of a lipoprotein profile related to an increased or decreased cardiovascular risk. It has been suggested that cholinesterase (ChE) could be induced by these drugs, something of undeniable interest as ChE appears to have a relation to the metabolism of lipoproteins. The serum activity of ChE was determined in a group of 90 adult epileptic patients (56 male and 34 female) treated with phenobarbital, phenytoin, and carbamazepine. The liver enzyme induction produced by these drugs was then evaluated by determining serum gamma-glutamyltranspherase activity and urinary excretion of D-glucaric acid. A significant increase of serum ChE (p < 0.005) was found in the group of patients compared to a control group (n = 49) with a similar distribution for age and sex. A significant correlation was found for both male and female patients between ChE and concentrations of triglycerides, phospholipids, cholesterol, low-density lipoprotein (LDL) phospholipids, LDL-cholesterol, and apolipoprotein B (p < 0.01). Similarly, in female patients, ChE had a significant correlation with the total cholesterol/high-density lipoprotein (HDL) cholesterol and LDL-cholesterol/HDL-cholesterol ratios (p < 0.01). The ChE/HDL-cholesterol relationship, which has been proposed as a marker for cardiovascular risk, presented significant correlations with the total cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios in patients of both sexes (p < 0.001). In the case of epileptic patients treated with enzyme-inducing anticonvulsant drugs, there may be an association between the possible induction of ChE and the metabolism of lipoproteins containing apolipoprotein B.

Toxicogenomics discrimination of potential hepatocarcinogenicity of non-genotoxic compounds in rat liver

Long-term carcinogenicity testing of a compound is exceedingly time-consuming and costly, and requires many test animals, whereas the Ames test, which is based on the assumption that any substance that is mutagenic may also exert carcinogenic potential, is useful as a short-term screening assay but has major drawbacks. Although, in fact, 90% of compounds that give a positive Ames test cause cancer in laboratory animals, a good proportion of compounds that give a negative Ames test are also carcinogens; that is, there is no good correlation between carcinogenicity and negative Ames test results. As an alternative to these two approaches, we have tried applying toxicogenomics to predict the carcinogenicity of a compound from the gene expression profile induced in vivo. To establish our model, male Sprague-Dawley rats were orally administered test compounds (12 hepatocarcinogens and 26 non-hepatocarcinogens) for 28 days. Analysis of liver gene expression data by Support Vector Machines (SVM) dividing compounds into 'for training' and 'for test' (20 cases assigned randomly) allowed a set of marker genes to be tested for prediction of hepatocarcinogenicity. The developed prediction model was then validated with reference to the concordance rate with training data and test data, and a good performance was obtained. We will have new gene expression data and continue the validation of our model.

Computational models to assign biopharmaceutics drug disposition classification from molecular structure

PURPOSE

We applied in silico methods to automatically classify drugs according to the Biopharmaceutics Drug Disposition Classification System (BDDCS).

MATERIALS AND METHODS

Models were developed using machine learning methods including recursive partitioning (RP), random forest (RF) and support vector machine (SVM) algorithms with ChemDraw, clogP, polar surface area, VolSurf and MolConnZ descriptors. The dataset consisted of 165 training and 56 test set molecules.

RESULTS

RF model 3, RP model 1, and SVM model 1 can correctly predict 73.1, 63.6 and 78.6% test compounds in classes 1, 2 and 3, respectively. Both RP and SVM models can be used for class 4 prediction. The inclusion of consensus analysis resulted in improved test set predictions for class 2 and 4 drugs.

CONCLUSIONS

The models can be used to predict BDDCS class for new compounds from molecular structure using readily available molecular descriptors and software, representing an area where in silico approaches could aid the pharmaceutical industry in speeding drugs to the patient and reducing costs. This could have significant applications in drug discovery to identify molecules that may have future developability issues.

Quantification of the expression and inducibility of 12 rat cytochrome P450 isoforms by quantitative RT-PCR

The administration of xenobiotics may significantly alter the expression of cytochromes P450 (CYPs), thereby leading to potentially toxic cellular, physiologic, and pharmacologic responses. Indeed, an important task in the development of new therapeutic entities is to evaluate efficiently and quantitatively their potential effects on the expression level of different CYPs. In this report, reverse transcriptase polymerase chain reaction (RT-PCR) was used to measure basal and induced mRNA of a wide range of rat CYP isoforms. Rats (n=3 per treatment) were treated with five prototype inducers of CYP isoforms or with vehicle only. RT and PCR efficiencies were determined using appropriate RNA and DNA standards. Messenger RNA was quantified by PicoGreen standard curves and normalized to cyclophilin. Quantitative RT-PCR was used successfully to demonstrate that CYP isoforms were induced at the mRNA level following drug administration. Notably, phenobarbital resulted in significant induction of CYP2B1, CYP2B2, CYP2C6, CYP2C13, CYP2E1, CYP3A1, and CYP3A2. 3-Methylcholanthrene induced CYP1A1, CYP1A2, and CYP1B1. CYP2C11 expression was highly variable and suppressed by pyridine, whereas the expression of CYP2E1 was suppressed by dexamethasone. We demonstrated that quantitative RT-PCR can be used to evaluate efficiently the effect of compounds on the expression of a wide range of CYP isoforms. The technique is advantageous over others in that it is very sensitive, efficient and applicable to highly homologous CYP isoforms.

Improving seizure control in dogs with refractory epilepsy using gabapentin as an adjunctive agent

OBJECTIVE

To assess whether there is a change in seizure activity in dogs with refractory epilepsy that are receiving appropriate doses of phenobarbitone and/or potassium bromide, when gabapentin is added to the therapeutic regimen.

DESIGN

A prospective study of 17 dogs with a refractory seizure disorder, 16 of which have idiopathic epilepsy.

PROCEDURE

Patients were stabilised using phenobarbitone and/or potassium bromide to produce tolerable therapeutic serum concentrations and dosed additionally with gabapentin at 35 to 50 mg/kg/d (divided twice or three times daily) for 4 months. Owners recorded seizure activity and side effects during this period in a standardised diary. Patients underwent monthly physical examinations and venepuncture to assess selected serum biochemical analytes, as well as phenobarbitone and bromide concentrations. Patients were further monitored for long-term response to adjunctive gabapentin therapy.

RESULTS

There was no significant decrease in the number of seizures over the study period for the entire cohort, however three dogs stopped seizuring completely. There was a significant increase in the number of patients who showed an increase in the interictal period (P > 0.001). Serum alkaline phosphatase activity and triglyceride concentrations were elevated at baseline. There were no significant changes in biochemical analytes during the course of the study period. Side effects observed initially on addition of gabapentin included sedation and hind limb ataxia. The former resolved spontaneously after a few days; the latter after a slight reduction in bromide dose. Long-term, a further two patients became seizure free and ten patients remained on gabapentin indefinitely. No long-term side effects have become apparent.

CONCLUSION

Addition of gabapentin to phenobarbitone and/or potassium bromide increased the interictal period and shortened the post-seizure recovery in some canine epileptics. In some dogs, seizures were prevented completely, while in others there was an increase in interictal period. The short-half life of gabapentin has advantages for seizure control, however its present high cost may prohibit therapy in large dogs.

Protective effect of a 50% hydroalcoholic fruit extract of Emblica officinalis against anti-tuberculosis drugs induced liver toxicity

The present report showed the hepatoprotective property of a 50% hydroalcoholic extract of the fruits of Emblica officinalis (fruit) (EO-50) against antituberculosis (anti-TB) drugs-induced hepatic injury. The biochemical manifestations of hepatotoxicity induced by rifampicin (RIF), isoniazid (INH) and pyrazinamide (PZA), either given alone or in combination were evaluated. In vitro studies were done on suspension cultures of rat hepatocytes while sub-acute studies were carried out in rats. The hepatoprotective activity of EO-50 was found to be due to its membrane stabilizing, antioxidative and CYP 2E1 inhibitory effects.

Drug induced hepatic focal nodular hyperplasia

Focal nodular hyperplasia, an uncommon benign hepatic tumor, has been reported following ingestion of various drugs and chemical agents. The authors report a case of a young girl who developed such lesion following ingestion of anti-tuberculosis drugs for the treatment of her abdominal tuberculosis.

Pharmacological management of neuropathic pain

In health, the nervous system exists in a balance between inhibitory and excitatory influences. This balance may be upset if neural tissue is damaged or irritated and may give rise to neuropathic pain. Such neuropathic pain does not respond consistently to opioid analgesics or NSAIDs and it may therefore be necessary to utilise other therapeutic agents with known activity on either the excitatory or inhibitory components of the pain pathway. These other agents are traditionally considered with reference to their original uses; we still refer to tricyclic antidepressants (TCAs) and anticonvulsant drugs when a consideration of their modes of action may allow more rational use. For example, carbamazepine is related to the TCAs by virtue of its chemical structure and proposed mode of action and yet is still classified as an anticonvulsant drug. With respect to the opioids, increasing evidence points to an analgesic effect in neuropathic pain, although concerns regarding tolerance and dependence still prevent more widespread use. The anticonvulsants comprise a group of compounds possessing anticonvulsant and analgesic properties, but each possesses differing modes of action and so several members of the class should be tried before a conclusion is reached that they, as a whole, are ineffective. TCAs may also have a role in the treatment of neuropathic pain. As with all drugs, if their use is not associated with pain relief in a defined period of time, their use should be terminated. Topical TCAs may also have a role where the area of neuropathic pain is small. Other options, such as SSRIs, membrane stabilisers, capsaicin, baclofen and clonidine may have potential in treating neuropathic pain. The available evidence regarding the efficacy of currently available agents for the treatment of neuropathic pain is sparse. With the knowledge of achieving analgesia, according to the modes of actions of various agents it is hoped that the treatment of this difficult condition may be more logical and successful.

Evaluation of interaction potential of certain concurrently administered drugs with pharmacological and pharmacokinetic profile of centchroman in rats

Centchroman (Ormeloxifene) is a nonsteroidal, selective estrogen receptor modulator, oral contraceptive and anticancer agent, and is intended for long-term use by women. In view of its vast clinical application and the interaction of steroidal oral contraceptives with certain commonly used therapeutic agents, evaluation of interaction of certain concomitantly administered therapeutic agents (ibuprofen, rifampicin, diazepam, salbutamol, nifedipine, paracetamol, haloperidol, and tetracycline), in terms of both the postcoital contraceptive efficacy and pharmacokinetic profile, with centchroman was undertaken in female Sprague-Dawley rats. Among the representatives from each commonly used therapeutic category, interaction (pharmacokinetic) was observed with ibuprofen (60 mg/kg, twice daily), haloperidol (0.7 mg/kg, twice daily), and tetracycline (140 mg/kg, twice daily) coadministration on Days 1 through 5 postcoitum. Of these three therapeutic agents, only tetracycline interfered with the contraceptive efficacy of centchroman. It reduced the bioavailability of centchroman and its active metabolite by increasing their excretion through bile and feces. Increased metabolite excretion on tetracycline coadministration indicates the enterohepatic recirculation of the metabolite, not the parent drug. However, the effect of tetracycline was negated by the inclusion of lactic acid bacillus spores in the regimen.

Focal nodular hyperplasia of the liver after intraconazole treatment

A 38-year-old woman developed focal nodular hyperplasia of the liver after she had received a 4-month treatment with intraconazole 200 mg/d for a fungal infection of her fingernails. Because the patient underwent yearly liver ultrasound examinations because of the removal of a breast carcinoma, when the tumor was discovered incidentally, it was clear that it had developed within the past year after she had begun receiving intraconazole. Although various chemical agents and drugs have been considered as possible etiologic factors in the development of focal nodular hyperplasia of the liver, cases occurring after intraconazole therapy have not been reported before. Apart from the theoretical considerations with regard to the pathogenesis of nodular hyperplasia of the liver, this case could gain practical importance, as it shows a new adverse effect of a drug that has been used in more than 34 million patients over the past 10 years. Furthermore, this case should draw attention to the possibility of drug-induced benign hepatic tumors, as they may mimic malignant and metastatic disorders, which might be especially alarming in patients undergoing routine examinations after removal of malignant tumors, such as our patient.