Clinical features and management of analgesic poisoning

Anticancer Drug Discovery By Structure-Based Repositioning Approach

Despite the tremendous progress that has occurred in recent years in cell biology and oncology, in chemical, physical and computer sciences, the disease cancer has continued as the major cause of death globally. Research organizations, academic institutions and pharmaceutical companies invest huge amounts of money in the discovery and development of new anticancer drugs. Though much effort is continuing and whatever available approaches are being attempted, the success of bringing one effective drug into the market has been uncertain. To overcome problems associated with drug discovery, several approaches are being attempted. One such approach has been the use of known, approved and marketed drugs to screen these for new indications, which have gained considerable interest. This approach is known in different terms as "drug repositioning or drug repurposing." Drug repositioning refers to the structure modification of the active molecule by synthesis, in vitro/ in vivo screening and in silico computational applications where macromolecular structure-based drug design (SBDD) is employed. In this perspective, we aimed to focus on the application of repositioning or repurposing of essential drug moieties present in drugs that are already used for the treatment of some diseases such as diabetes, human immunodeficiency virus (HIV) infection and inflammation as anticancer agents. This review thus covers the available literature where molecular modeling of drugs/enzyme inhibitors through SBDD is reported for antidiabetics, anti-HIV and inflammatory diseases, which are structurally modified and screened for anticancer activity using respective cell lines.

Comparison of Patient Questionnaires and Plasma Assays in Intentional Drug Overdoses

Our aim was to explore the agreement between clinically collected information on purported drug intake and plasma data in intentional drug overdose. We included all subjects with intentional drug overdose above 15 years of age consecutively admitted to the Emergency Department of the University Hospital during 4 months. Information about drugs used and sources of this information was collected and compared to presence of drug in plasma, concerning four drugs with high toxic potential (tricyclic antidepressants, meprobamate, paracetamol and ethanol). Sensitivity, specificity, predictive positive and negative values of all sources of information pooled were assessed for each drug. 413 intentional drug overdoses were included, 66% with more than one drug. According to clinical information, 8% took tricyclic antidepressants, 11% meprobamate, 9% paracetamol and 41% ethanol. Systematic plasma assays confirmed this in 59% of cases for tricyclic antidepressants, 76% for meprobamate and ethanol, and 77% for paracetamol. Plasma concentrations were considered toxic in 28% of cases for tricyclic antidepressants, 65% for meprobamate, 43% for ethanol and never for paracetamol. Tricyclic antidepressants and meprobamate were found unexpectedly in 3%, paracetamol in 7% and ethanol in 6%. Toxic concentrations were found only with meprobamate. The risk of erroneous, clinically collected information was greater by excess (25 to 40% false positives) than by lack (3 to 7% false negatives). Thus, the consequences of erroneous, clinically collected information were probably more excess cost for the institution than medical risk for the patients. However these results found at the population level may not be true at an individual level.

Analysis of the glutathione conjugate of paracetamol in human liver microsomal fraction by liquid chromatography mass spectrometry

An assay based on microbore liquid chromatography-positive ion electrospray mass spectrometry with selected ion recording has been developed for the measurement of the glutathione conjugate of paracetamol (acetaminophen) in human hepatic microsomal incubations. A deuterated analogue of the glutathione conjugate was synthesized for use as an internal standard and extraction was carried out on Oasis solid phase extraction columns. The limit of quantification of the glutathione conjugate was 10 ng/incubation and the intra-assay coefficient of variation at this concentration was 6.8%.

Comparison of paracetamol-induced hepatotoxicity in the rat in vivo with progression of cell injury in vitro in rat liver slices

The flux in rat hepatic ratio of adenosine triphosphate levels to adenosine diphosphate levels (ATP/ADP) during the onset and progression of paracetamol-induced cell injury both in vivo and in vitro were investigated and compared. Leakage of lactate dehydrogenase (LDH) and potassium (K+), and mg water/mg dry weight quantified cell injury. ATP and ADP levels were determined using the luciferin-luciferase bioluminescence assay. For in vitro studies, liver slices obtained from phenobarbitone-induced rats were exposed to 10 mM paracetamol for 120 min (T0-T120) and, then incubated without paracetamol up to a further 240 min (T120-T360). For in vivo studies, groups of four phenobarbitone-induced rats received i.p. injections of 800 mg/kg paracetamol. ATP/ADP ratios fall upon exposure to paracetamol both in vitro and in vivo. However, unlike the in vitro situation where the fall in ATP/ADP ratios precedes and accompanies the progression of cell injury, the in vivo fall in ATP/ADP ratios is shown to occur as cell injury measurements begin to recover to control levels. However, despite these differences classic paracetamol-induced centrilobular necrosis is observed to occur both in vitro and in vivo. This study demonstrates that the liver slice model is a simple and useful technique to investigate the underlying mechanisms of paracetamol-induced cell injury.

Salicylate Intoxication

Aspirin (acetylsalicylic acid) is one of the most widely used over-the-counter medications. Because of its availability and widespread use, aspirin has a long history of human toxicity from accidental or intentional overdosing. According to the American Association of Poison Control Centers aspirin was implicated in 19083 exposures in 1995, with 11800 cases treated in a health care facility, and 52 associated deaths. Aspirin toxicity may be a life-threatening condition that produces multiple system organ failure requiring treatment in an intensive care unit. Managing a patient with salicylism will challenge the skills of the critical care team, especially in the areas of life support, fluid and electrolyte balance, and acid-base management. This article reviews the physiology, pathophysiology, acute and chronic salicylism in children and adults, and management of salicylate intoxication.

Comparison of protection by fructose against paracetamol injury with protection by glucose and fructose-1,6-diphosphate

We have compared the protective effect of fructose in normal Ringer solution during the onset and progression of cell injury induced by paracetamol in rat liver slices with the protective effect of glucose and fructose-1,6-diphosphate. Liver slices obtained from phenobarbitone-induced and non-induced rats were used in a model in vitro system. Slices were exposed to 10 mM paracetamol for 120 min and then incubated without paracetamol in the presence or absence of protective agents for a further 240 min. Cell injury was quantified by measuring leakage of lactate dehydrogenase (LDH) and potassium (K+). Adenosinetriphosphate (ATP) levels were measured using the luciferin-luciferase bioluminescence assay. Addition of higher concentrations of glucose (10-50 mM) to Ringer solution were not found to result in protection at the end of incubation in paracetamol-treated slices obtained from phenobarbitone-induced rats. Neither did sucrose nor mannitol protect. However, exclusion of glucose from Ringer solution resulted in cell injury in paracetamol-treated slices obtained from non-induced rats. Methionine, a known antidote for paracetamol poisoning, failed to protect in this instances but fructose did protect. This suggests that the presence of a glycolytic substrate plays a crucial role in cell protection. Further evidence for this is the finding that iodoacetate, an inhibitor of glycolysis, not only increase cell injury in paracetamol-treated slices but also reverses fructose protection. Fructose-1,6-diphosphate was found to protect against the onset and progression of cell injury in paracetamol-treated slices obtained from phenobarbitone induced rats. This protective agent is found to maintain high ATP levels and cell viability in paracetamol-treated slices at a time when paracetamol-treated slices show a profound loss of ATP levels and a significant increase in cell injury as measured by leakage of LDH and K+.

Cell protection by fructose is independent of adenosine triphosphate (ATP) levels in paracetamol injury to rat liver slices

Fructose protects cells against several types of injury but the mechanism of protection is uncertain. We have used paracetamol injury in rat liver slices as a model system to investigate the role of ATP levels in protection by fructose. Fructose depletes ATP levels in a concentration-dependent fashion in liver slices obtained from non-induced rats. Liver slices recover their ATP levels in the presence of fructose concentrations up to 10 mM. However, in the presence of of 20mM fructose, ATP levels are depleted for the duration of 240 min incubation. Adenine at 100 microM reverses the ATP depletion induced by 20 mM fructose in slices over 240 min incubation. Liver slices obtained from phenobarbitone induced rats were exposed to 10 mM paracetamol for 120 min and, then, incubated without paracetamol, with or without fructose for another 240 min. Introduction of 10 mM or 20 mM fructose in the second stage of incubation prevents paracetamol-induced injury. Fructose at 20 mM induces a rapid and marked depletion in slice ATP levels and these remain low throughout the second 240 min incubation period. Fructose at 10 mM maintains high ATP levels, even in paracetamol-treated slices. There is a profound protective effect against paracetamol-induced injury by either concentration. This suggests that protection is not dependent on high or on low ATP levels. Incubation of paracetamol-treated slices in the presence of 20 mM fructose plus 100 microM adenine in the second 240 min incubation period still results in the same level of protection as with 20 or 10 mM fructose along while reversing the ATP depletion observed with 20 mM fructose.

Electron transport and protection of liver slices in the late stage of paracetamol injury

Cell injury by chemicals takes place in two stages, initial chemical interaction between the material and cell components, and subsequent stages of adaptation or failure of response to chemical modification of some parts of the cell apparatus. Paracetamol toxicity was studied in an in vitro system using liver slices incubated in two stages. During the first 2 hr slices were exposed to 10 mM paracetamol and this was absent during the following 4 hr of incubation. Damage was quantified at the end by measuring leakage of lactate dehydrogenase (LDH), increase in water content and potassium loss. Treatment of slices with 10 microM DCPIP or 2 mM ethanol in the second period of incubation prevented paracetamol-induced damage. The protective effect was not dependent on the activity of P450 since the second stage of incubation was insensitive to SKF-525A. The protective effect of ethanol was blocked by the presence of 1 mM pyrazole suggesting that ethanol needs to be metabolized to exert its effect. The addition of 20 mM pyruvate reversed the protection provided by ethanol. Nicotinamide did not alter toxicity or protection by ethanol. These findings suggest an increase of NADH and NADH/NAD ratio as the most probable explanation for the protective effect observed. The role of reducing equivalents in detoxification of quinones such as NAPQI by formation of hydroquinones, is discussed in relation to the mechanism of cell injury by paracetamol.