Plasma persistence of 2-aminothiazoline-4-carboxylic acid in rat system determined by liquid chromatography tandem mass spectrometry.

2-Aminothiazoline-4-carboxylic acid (ATCA) was intravenously injected to rats in order to investigate its plasma distribution. ATCA was extracted from plasma samples by solid phase extraction (SPE) and molecularly imprinted polymer stir bar sorption extraction (MIP-SBSE). Detection and quantification of ATCA were achieved by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). It was found that the intravenously injected ATCA concentration quickly decreased to half within 2.5h in the rat system. However, after 2.5 h, the concentration of ATCA in plasma stayed constant at least 5 folds above the endogenous ATCA level for more then 48 h. This finding can be used for evaluating ATCA's diagnostic and forensic value as a biomarker for cyanide exposure.

Nano-intercalated rhodanese in cyanide antagonism.

Present studies have focused on nano-intercalated rhodanese in combination with sulfur donors to prevent cyanide lethality in a prophylactic mice model for future development of an effective cyanide antidotal system. Our approach is based on the idea of converting cyanide to the less toxic thiocyanate before it reaches the target organs by utilizing sulfurtransferases (e.g., rhodanese) and sulfur donors in a close proximity by injecting them directly into the blood stream. The inorganic thiosulfate (TS) and the garlic component diallydisulfide (DADS) were compared as sulfur donors with the nano-intercalated rhodanese in vitro and in vivo. The in vivo and in vitro experiments showed that DADS is not a more efficient sulfur donor than TS. However, the utilization of external rhodanese significantly enhanced the in vivo efficacy of both sulfur donor-nitrite combinations, indicating the potential usefulness of enzyme nano-delivery systems in developing antidotal therapeutic agents.

The analysis of 2-amino-2-thiazoline-4-carboxylic acid in the plasma of smokers and non-smokers.

ATCA (2-amino-2-thiazoline-4-carboxylic acid) is a promising marker to assess cyanide exposure because of several advantages of ATCA analysis over direct determination of cyanide and alternative cyanide biomarkers (i.e. stability in biological matrices, consistent recovery, and relatively small endogenous concentrations). Concentrations of ATCA in the plasma of smoking and non-smoking human volunteers were analyzed using gas-chromatography mass-spectrometry to establish the feasibility of using ATCA as a marker for cyanide exposure. The levels of ATCA in plasma of smoking volunteers, 17.2 ng/ml, were found to be significantly (p < 0.001) higher than that of non-smoking volunteers, 11.8 ng/ml. Comparison of ATCA concentrations of smokers relative to non-smokers in both urine and plasma yielded relatively similar results. The concentration ratio of ATCA for smokers versus non-smokers in plasma and urine was compared to similar literature studies of cyanide and thiocyanate, and correlations are discussed. This study supports previous evidence that ATCA can be used to determine past cyanide exposure and indicates that further studies should be pursued to validate the use of ATCA as a marker of cyanide exposure.

The pharmacological properties of anisodamine.

Anisodamine is a naturally occurring atropine derivative that has been isolated, synthesized and characterized by scientists in the People's Republic of China. Like atropine and scopolamine, anisodamine is a non-specific cholinergic antagonist exhibiting the usual spectrum of pharmacological effects of this drug class. It appears to be less potent and less toxic than atropine and displays less CNS toxicity than scopolamine. Anisodamine has been shown to interact with and disrupt liposome structure which may reflect its effects on cellular membranes. Experimental evidence implicates anisodamine as an anti-oxidant that may protect against free radical-induced cellular damage. Its cardiovascular properties include depression of cardiac conduction and the ability to protect against arrhythmia induced by various agents. Anisodamine is a relatively weak alpha(1) adrenergic antagonist which may explain its vasodilating activity. Its anti-thrombotic activity may be a result of inhibition of thromboxane synthesis. The T(1/2) of anisodamine in humans is about 2-3 h. Numerous therapeutic uses of anisodamine have been proposed including treatment of septic shock, various circulatory disorders, organophosphorus (OP) poisoning, migraine, gastric ulcers, gastrointestinal colic, acute glomerular nephritis, eclampsia, respiratory diseases, rheumatoid arthritis, obstructive jaundice, opiate addiction, snake bite and radiation damage protection. The primary therapeutic use of anisodamine has been for the treatment of septic shock. Several mechanisms have been proposed to explain its beneficial effect though most mechanisms are based upon the assumption that anisodamine ultimately acts by an improvement of blood flow in the microcirculation. Preliminary studies suggest another important therapeutic use of anisodamine is for the treatment of OP poisoning. Additional research is needed to delineate further the clinical usefulness of anisodamine relative to other anti-muscarinic drugs such as atropine and scopolamine.

Effect of octanol:water partition coefficients of organophosphorus compounds on biodistribution and percutaneous toxicity.

Knowledge of partition coefficient (log P) data can play a critical role in understanding the pharmacokinetic and pharmacodistributive properties of toxic organophosphorus (OP) compounds. Using a recently published gas chromatographic method, the octanol:water log P values for the compounds tabun (GA), sarin (GB), cyclosarin (GF), and O-ethyl-S-(2-diisopropylaminoethyl) methylphosphonothiolate (VX) were determined to be 0.384 +/- 0.033, 0.299 +/- 0.016, 1.038 +/- 0.055, and 0.675 +/- 0.070, respectively. Based on these data, the log P value of the fluorophosphonate fragment, common to GB, soman (GD), and GF, was determined to be -2.256 +/- 0.273. The predictive value for absorption and distribution of the determined log P values was compared to measured values. The time to onset of local fasciculations (47.3, 29.0, 8.8, 8.5, and 6.3 min, respectively) in guinea pigs exposed percutaneously to equilethal doses of GA, VX, GF, GB, or GD was used as an indicator of dermal penetration. There was a good correlation (r = 0.95) between the measured log P value and the rate of onset of local fasciculations. Assuming a direct correspondence, equilibrium tissue:blood log P may be estimated from octanol:water log P. Comparison of the estimated and directly measured tissue:blood log P revealed a correlation of 0.8 for GD in liver, muscle, and adipose tissue. Our results demonstrate the use of log P data to both predict absorption and determine the distribution of OP compounds in tissues. This facilitates further estimates of in vivo OP effects from in vitro experiments.

Spectrophotometric Analysis of the Cyanide Metabolite 2-Aminothiazoline-4-Carboxylic Acid (ATCA).

Methods of directly evaluating cyanide levels are limited by the volatility of cyanide and by the difficulty of establishing steady-state cyanide levels with time. We investigated the measurement of a stable, toxic metabolite, 2-aminothiazoline-4-carboxylic acid (ATCA), in an attempt to circumvent the challenge of directly determining cyanide concentrations in aqueous media. This study was focused on the spectrophotometric ATCA determination in the presence of cyanide, thiocyanate (SCN(-)), cysteine, rhodanese, thiosulfate, and other sulfur donors. The method involves a thiazolidine ring opening in the presence of p-(hydroxy-mercuri)-benzoate, followed by the reaction with diphenylthiocarbazone (dithizone). The product is spectrophotometrically analyzed at 625 nm in carbon tetrachloride. The calibration curve was linear with a regression line of Y = 0.0022x (R(2) = 0.9971). Interference of cyanide antidotes with the method was determined. Cyanide, thiosulfate, butanethiosulfonate (BTS), and rhodanese did not appreciably interfere with the analysis, but SCN(-) and cysteine significantly shifted the standard curve. This sensitive spectrophotometric method has shown promise as a substitute for the measurement of the less stable cyanide.

Determination of the cyanide metabolite 2-aminothiazoline-4-carboxylic acid in urine and plasma by gas chromatography-mass spectrometry.

The cyanide metabolite 2-aminothiazoline-4-carboxylic acid (ATCA) is a promising biomarker for cyanide exposure because of its stability and the limitations of direct determination of cyanide and more abundant cyanide metabolites. A simple, sensitive, and specific method based on derivatization and subsequent gas chromatography-mass spectrometry (GC-MS) analysis was developed for the identification and quantification of ATCA in synthetic urine and swine plasma. The urine and plasma samples were spiked with an internal standard (ATCA-d(2)), diluted, and acidified. The resulting solution was subjected to solid phase extraction on a mixed-mode cation exchange column. After elution and evaporation of the solvent, a silylating agent was used to derivatize the ATCA. Quantification of the derivatized ATCA was accomplished on a gas chromatograph with a mass selective detector. The current method produced a coefficient of variation of less than 6% (intra- and interassay) for two sets of quality control (QC) standards and a detection limit of 25 ng/ml. The applicability of the method was evaluated by determination of elevated levels of ATCA in human urine of smokers in relation to non-smokers for both males and females.

Species comparison of methemoglobin reductase.

Methemoglobin (MHb) formation is effective in treating cyanide (CN) poisoning. Endogenous activity of the enzyme MHb reductase (MR) reflects the capacity to reduce MHb and thus represents a key factor for evaluating anti-CN efficacy of MHb formers. MR activity was measured in whole blood of nine animal species and was compared with human MR activity. The animals in this comparative study included seven nonhuman primate (NHP) species, the beagle dog, and the ferret. Although exhibiting higher MR activity than in humans, the rhesus and aotus NHPs' average MR activity was the closest to humans', with raw data from each NHP showing overlap with human raw data. The beagle dog, used extensively to study anti-CN characteristics of MHb formers, was the sole species that displayed MR activity lower than in humans, with no data overlap. Based on MR activity, the rhesus and aotus NHPs may each represent a more accurate model for predicting human responses to MHb formers. The data from this study provides a unique interspecies enzyme comparison, which should facilitate future rational development of anti-CN MHb formers.

The toxicokinetics of cyanide and mandelonitrile in the horse and their relevance to the mare reproductive loss syndrome.

The epidemiological association between black cherry trees and mare reproductive loss syndrome has focused attention on cyanide and environmental cyanogens. This article describes the toxicokinetics of cyanide in horses and the relationships between blood cyanide concentrations and potentially adverse responses to cyanide. To identify safe and humane blood concentration limits for cyanide experiments, mares were infused with increasing doses (1-12 mg/min) of sodium cyanide for 1 h. Infusion at 12 mg/min produced clinical signs of cyanide toxicity at 38 min; these signs included increased heart rate, weakness, lack of coordination, loss of muscle tone, and respiratory and behavioral distress. Peak blood cyanide concentrations were about 2500 ng/mL; the clinical and biochemical signs of distress reversed when infusion stopped. Four horses were infused with 1 mg/min of sodium cyanide for 1 h to evaluate the distribution and elimination kinetics of cyanide. Blood cyanide concentrations peaked at 1160 ng/mL and then declined rapidly, suggesting a two-compartment, open model. The distribution (alpha) phase half-life was 0.74 h, the terminal (beta phase) half-life was 16.16 h. The mean residence time was 12.4 h, the steady-state volume of distribution was 2.21 L/kg, and the mean systemic clearance was 0.182 L/h/kg. Partitioning studies showed that blood cyanide was about 98.5% associated with the red cell fraction. No clinical signs of cyanide intoxication or distress were observed during these infusion experiments. Mandelonitrile was next administered orally at 3 mg/kg to four horses. Cyanide was rapidly available from the orally administered mandelonitrile and the C max blood concentration of 1857 ng/mL was observed at 3 min after dosing; thereafter, blood cyanide again declined rapidly, reaching 100 ng/mL by 4 h postadministration. The mean oral bioavailability of cyanide from mandelonitrile was 57% +/- 6.5 (SEM), and its apparent terminal half-life was 13 h +/- 3 (SEM). No clinical signs of cyanide intoxication or distress were observed during these experiments. These data show that during acute exposure to higher doses of cyanide (~600 mg/horse; 2500 ng/mL of cyanide in blood), redistribution of cyanide rapidly terminated the acute toxic responses. Similarly, mandelonitrile rapidly delivered its cyanide content, and acute cyanide intoxications following mandelonitrile administration can also be terminated by redistribution. Rapid termination of cyanide intoxication by redistribution is consistent with and explains many of the clinical and biochemical characteristics of acute, high-dose cyanide toxicity. On the other hand, at lower concentrations (<100 ng/mL in blood), metabolic transformation of cyanide is likely the dominant mechanism of termination of action. This process is slow, with terminal half-lives ranging from 12-16 hours. The large volume of distribution and the long terminal-phase-elimination half-life of cyanide suggest different mechanisms for toxicities and termination of toxicities associated with low-level exposure to cyanide. If environmental exposure to cyanide is a factor in the cause of MRLS, then it is likely in the more subtle effects of low concentrations of cyanide on specific metabolic processes that the associations will be found.

Age-associated changes of responses to acetylsalicylic acid.

Aspirin can be an effective antipyretic, analgesic and anti-inflammatory agent, but unfortunately, its use in the elderly is often excessive [43]. In a survey by Gillies and Skyring, the overall prevalence of daily aspirin intake was greater in middle-age and older-age groups than for those of less than 40 years of age [16]. The elderly are susceptible to the advertising of non-prescription drugs and aspirin is frequently self-prescribed [8,31]. Age-related physiological changes modify the response to aspirin in the elderly. A higher incidence of drug reactions and interactions has been evidenced in this age group. The cases cited throughout this report substantiate the need for caution on the part of the geriatric patient and the physician in regard to aspirin therapy for the elderly.