trimedoxime-bromide and pralidoxime

The use of organophosphorus pesticides results in toxicity risk to non-target organisms. Organophosphorus compounds share a common mode of action, exerting their toxic effects primarily via acetylcholinesterase (AChE) inhibition. Consequently, acetylcholine accumulates in the synaptic clefts of muscles and nerves, leading to overstimulation of cholinergic receptors. Acute cholinergic crisis immediately follows exposure to organophosphate and includes signs and symptoms resulting from hyperstimulation of central and peripheral muscarinic and nicotinic receptors. The current view of the treatment of organophosphate poisoning includes three strategies, i.e. the use of an anticholinergic drug (e.g., atropine), cholinesterase-reactivating agents (e.g., oximes) and anticonvulsant drugs (e.g., benzodiazepines). Oximes, as a part of antidotal therapy, ensure the recovery of phosphylated enzymes via a process denoted as reactivation of inhibited AChE. However, both experimental results and clinical findings have demonstrated that different oximes are not equally effective against poisonings caused by structurally different organophosphorus compounds. Therefore, antidotal characteristics of conventionally used oximes can be evaluated regarding how close the certain substance is to the theoretical concept of the universal oxime. Pralidoxime (PAM-2), trimedoxime (TMB-4), obidoxime (LüH-6), HI-6 and HLö-7 have all been demonstrated to be very effective in experimental poisonings with sarin and VX. TMB-4 and LüH-6 may reactivate tabun-inhibited AChE, whereas HI-6 possesses the ability to reactivate the soman-inhibited enzyme. An oxime HLö-7 seems to be an efficient reactivator of AChE inhibited by any of the four organophosphorus warfare agents. According to the available literature, the oximes LüH-6 and TMB-4, although relatively toxic, are the most potent to induce reactivation of AChE inhibited by the majority of organophosphorus pesticides. Since there are no reports of controlled clinical trials on the use of TMB-4 in human organophosphate pesticide poisoning, LüH-6 may be a better option.

Topics: Acetylcholinesterase; Antidotes; Chemical Warfare Agents; Cholinesterase Reactivators; Clinical Trials as Topic; Drug-Related Side Effects and Adverse Reactions; Humans; Insecticides; Obidoxime Chloride; Organophosphate Poisoning; Organothiophosphorus Compounds; Oximes; Pralidoxime Compounds; Sarin; Trimedoxime

The A-series is the most recent generation of chemical warfare nerve agents (CWA) which act directly on the inhibition of the human acetylcholinesterase (HssAChE) enzyme. These compounds lack accurate experimental data on their physicochemical properties, and there is no evidence that traditional antidotes effectively reactivate HssAChE inhibited by them. In the search for potential antidotes, we employed virtual screening, molecular docking, and molecular dynamics (MD) simulations for the theoretical assessment of the performance of a library of Mannich phenols as potential reactivators of HssAChE inhibited by the Novichok agents A-230, A-232, and A-234, in comparison with the commercial oximes pralidoxime (2-PAM), asoxime (HI-6), trimedoxime (TMB-4), and obidoxime. Following the near-attack conformation (NAC) approach, our results suggest that the compounds assessed would face difficulties in triggering the proposed nucleophilic in-line displacement mechanism. Despite this, it was observed that certain Mannich phenols presented similar or superior results to those obtained by reference oximes against A-232 and A-234 model, suggesting that these compounds can adopt more favourable conformations. Additional binding energy calculations confirmed the stability of the model/ligands complexes and the reactivating potential observed in the molecular docking and MD studies. Our findings indicate that the Mannich phenols could be alternative antidotes and that their efficacy should be evaluated experimentally against the A-series CWA.

Topics: Acetylcholinesterase; Antidotes; Chemical Warfare Agents; Cholinesterase Inhibitors; Cholinesterase Reactivators; Humans; Molecular Docking Simulation; Nerve Agents; Oximes; Pyridinium Compounds; Trimedoxime

Beside the key inhibition of acetylcholinesterase (AChE), involvement of oxidative stress in organophosphate (OP)-induced toxicity has been supported by experimental and human studies. On the other hand, according to our best knowledge, possible antioxidant properties of oximes, the only causal antidotes to OP-inhibited AChE, have been examined only by a few studies. Thus, we have determined the effect of four conventional (obidoxime, trimedoxime, pralidoxime, asoxime) and two promising experimental oximes (K027, K203) on dichlorvos (DDVP)-induced oxidative changes in vivo. Wistar rats (5/group) were treated with oxime (5% LD

Topics: Animals; Aryldialkylphosphatase; Biomarkers; Brain; Cholinesterase Inhibitors; Dichlorvos; Male; Malondialdehyde; Obidoxime Chloride; Organophosphate Poisoning; Oxidative Stress; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Rats; Superoxide Dismutase; Trimedoxime

The kinetics of oxime-induced reactivation of malathion-inhibited cholinesterase has been experimentally studied in vitro. It is shown that oximes do not restore the activity of inhibited butyrylcholinesterase. Acetylcholinesterase reactivation peak (5-mins long) was found to take place upon introduction of dipyroxime (32.5%), pralidoxime (18%), carboxyme (16%) at a concentration of 2.5 x 10(-4) mol/l or toxogonine (26%) at a concentration of 5 x 10(-4) mol/l. Toxogonine demonstrated the maximum affinity to phosphorylated enzyme, while dipyroxime is characterized by a high reactivity with respect to oxime. Significant reactivating ability of these preparations (kR -2300 mol(-1) min(-1) makes them promising solution for the treatment of malathion intoxication.

Topics: Acetylcholinesterase; Animals; Antidotes; Butyrylcholinesterase; Cholinesterase Inhibitors; Cholinesterase Reactivators; Enzyme Activation; Erythrocytes; Horses; Kinetics; Malathion; Obidoxime Chloride; Pralidoxime Compounds; Solutions; Torpedo; Trimedoxime

Administration of acetylcholinesterase (AChE) reactivators (oximes) is usually used in order to counteract the poisoning effects of nerve agents. The possibility was suggested that oximes may show some therapeutic and/or adverse effects through their action in central nervous system. There are no sufficient data about interaction of oximes with monoaminergic neurotransmitter's systems in the brain. Oxime-type AChE reactivators pralidoxime, obidoxime, trimedoxime, methoxime and HI-6 were tested for their potential to affect the activity of monoamine oxidase of type A (MAO-A) and type B (MAO-B) in crude mitochondrial fraction of pig brains. The compounds were found to inhibit fully MAO-A with half maximal inhibitory concentration (IC(50)) of 0.375 mmol/l (pralidoxime), 1.53 mmol/l (HI-6), 2.31 mmol/l (methoxime), 2.42 mmol/l (obidoxime) and 4.98 mmol/l (trimedoxime). Activity of MAO-B was fully inhibited by HI-6 and pralidoxime only with IC(50) 4.81 mmol/l and 11.01 mmol/l, respectively. Methoxime, obidoxime and trimedoxime displayed non-monotonic concentration dependent effect on MAO-B activity. Because oximes concentrations effective for MAO inhibition could not be achieved in vivo at the cerebral level, we suppose that oximes investigated do not interfere with brain MAO at therapeutically relevant concentrations.

Topics: Animals; Brain; Cholinesterase Reactivators; Monoamine Oxidase; Monoamine Oxidase Inhibitors; Obidoxime Chloride; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Swine; Trimedoxime

Malathion is an organophosphate (OP) pesticide whose toxicity depends on its bioactivation to malaoxon. Human malathion poisoning has been treated with oximes (mainly pralidoxime) in an attempt to reactivate OP-inhibited acetylcholinesterase (AChE). However, pralidoxime has shown unsatisfactory therapeutic effects in malathion poisoning and its routine use has been questioned. In this study, we evaluated the in vitro potency of standards and newly developed oximes in reactivating malaoxon-inhibited AChE derived from mouse brain supernatants. Malaoxon displayed a concentration-dependent inhibitory effect on mouse brain AChE (IC(50) = 2.36 microM), and pralidoxime caused a modest reactivating effect (30% of reactivation at 600 microM). Obidoxime and trimedoxime, as well as K047 and K075, displayed higher reactivating effects (from 55% to 70% of reactivation at 600 muM) when compared with pralidoxime. The results show that obidoxime, trimedoxime, K074 and K075 present higher reactivating effects on malaoxon-inhibited AChE under in vitro conditions when compared with pralidoxime. Taking into account the unsatisfactory effects of pralidoxime as antidotal treatment in malathion poisonings, the present results suggest that obidoxime, trimedoxime, K074 and K075 might be interesting therapeutic strategies to reactivate malaoxon-inhibited AChE in malathion poisonings.

Topics: Acetylcholinesterase; Animals; Antidotes; Brain; Butanes; Cholinesterase Inhibitors; Cholinesterase Reactivators; Enzyme Repression; Insecticides; Malathion; Male; Mice; Obidoxime Chloride; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Trimedoxime

Introduction. The new K-oximes, K-27 [1-(4-hydroxyimino-methylpyridinium)-4-(4-carbamoylpyridinium) propane dibromide] and K-48 [1-(4-hydroxyimino-methylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide], show good in vitro efficacy in protecting acetylcholinesterase from inhibition by different organophosphorus compounds (OPCs), including nerve agents. To assess their efficacy in vivo, the extent of oxime-conferred protection from mortality induced by diisopropylfluorophosphate (DFP) was quantified and compared with that of five established oximes. Materials and Methods. Rats received DFP intraperitoneally in a dosage of 6, 8, or 10 micromol/rat and immediately thereafter intraperitoneal injections of K-27, K-48, pralidoxime, obidoxime, trimedoxime, methoxime, or HI-6. The relative risk (RR) of death over time (48 h) was estimated by Cox survival analysis, comparing results with the no-treatment group. Results. Best protection was observed when K-27 was used, reducing the RR of death to 19% of control RR (p < or = 0.005), whereas obidoxime (RR = 26%, p < or = 0.01), K-48 (RR = 29%, p < or = 0.005) and methoxime (RR = 26%, p < or = 0.005) were comparable. The RR of death was reduced only to about 35% of control by HI-6, to 45% by trimedoxime, and to 59% by 2-PAM (p < or = 0.005). Whereas the differences between the best oximes (K-27, obidoxime, methoxime, and K-48) were not statistically significant; these four oximes were significantly more effective than 2-PAM (p < or = 0.05). The efficacy of K-27 was also significantly higher than that of HI-6, trimedoxime, and 2-PAM (p < or = 0.05). Conclusion. Our data provide further evidence that K-27 is a very promising candidate for the treatment of intoxication with a broad spectrum of OPCs.

Topics: Animals; Cholinesterase Inhibitors; Cholinesterase Reactivators; Isoflurophate; Male; Obidoxime Chloride; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Rats; Rats, Wistar; Trimedoxime

In vitro comparison of reactivation efficacy of five currently used oximes - pralidoxime, obidoxime, trimedoxime, methoxime, and HI-6 (at two concentrations: 10-5 and 10-3 M) - against acetylcholinesterase (AChE; E.C. 3.1.1.7) inhibited by six different nerve agents (VX, Russian VX, sarin, cyclosarin, tabun, soman) and organophosphorus insecticide chlorpyrifos was the aim of this study. As a source of AChE in the experiments, rat brain homogenate was used. According to the results obtained, no AChE reactivator was able to reach sufficient potency for AChE inhibited by all nerve agents used. Moreover, oxime HI-6 (the most effective one) was not able to reactivate tabun- and soman-inhibited AChE. Due to this fact, it could be designated as a partially broad-spectrum reactivator.

Topics: Animals; Brain; Chemical Warfare Agents; Chlorpyrifos; Cholinesterase Inhibitors; Cholinesterase Reactivators; Dose-Response Relationship, Drug; Obidoxime Chloride; Organophosphates; Organophosphorus Compounds; Organothiophosphorus Compounds; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Rats; Rats, Wistar; Sarin; Soman; Tissue Extracts; Trimedoxime

The efficacy of H oximes (HI-6, HLö-7), the oxime BI-6, and currently used oximes (pralidoxime, obidoxime, trimedoxime) to reactivate acetylcholinesterase inhibited by two nerve agents (tabun, VX agent) was tested in vitro. Both H oximes (HI-6, HLö-7) and the oxime BI-6 were found to be more efficacious reactivators of VX-inhibited acetylcholinesterase than pralidoxime and obidoxime. On the other hand, their potency to reactivate tabun-inhibited acetylcholinesterase was low and did not reach the reactivating efficacy of trimedoxime and obidoxime. Thus, none of these compounds can be considered to be a broad-spectrum reactivator of nerve agent-inhibited acetylcholinesterase in spite of high potency to reactivate acetylcholinesterase inhibited by some nerve agents. More than one oxime may be necessary for the antidotal treatment of nerve agent-exposed individuals.

Topics: Acetylcholinesterase; Animals; Antidotes; Brain; Chemical Warfare Agents; Cholinesterase Inhibitors; Cholinesterase Reactivators; Male; Obidoxime Chloride; Organophosphates; Organothiophosphorus Compounds; Oximes; Pralidoxime Compounds; Pyridines; Pyridinium Compounds; Rats; Rats, Wistar; Trimedoxime

Inhibition of acetylcholinesterase (AChE) in human brain caused by phoxim or phoxim oxon, their reactivation with oxime and aging of phosphorylated AChE were studied and compared in vitro.. Micro-colorispectrophotometric assay was used to determine the activity of AChE.. The pI(50) of inhibition of AChE in human brain by phoxim and phoxim oxon were 5.39 and 5.77, respectively, whereas the pI(90) were 4.60 and 5.00, respectively. The reactivation rate of 0.1 mmol/L of pralidoxime (2-PAM), obidoxime (LüH(6)), trimedoxime (TMB-4) and pyramidoxime (HI-6) for phoxim-inhibited AChE in human brain was 65%, 97%, 91% and 56%, respectively, and their reactivation rate for phoxim oxon-inhibited AChE in human brain was 97%, 87%, 99% and 89%, respectively. The optimal reactivator for phoxim and phoxim oxon-inhibited AChEs was LüH(6) and TMB-4, respectively. The half aging time of phoxim and phoxim oxon inhibited phosphorylated AChEs were 39 and 28 hours, respectively, and the 99% aging time were 256 and 186 hours, respectively.. LüH(6) or TMB-4 should be used at the earlier as possible after poisoning with phoxim and phoxim oxon, and the reactivator should be consecutively used for more than seven days, even after their acute symptoms have been well controlled.

Topics: Acetylcholinesterase; Brain; Cholinesterase Inhibitors; Cholinesterase Reactivators; Enzyme Stability; Humans; In Vitro Techniques; Obidoxime Chloride; Organothiophosphorus Compounds; Oximes; Paraoxon; Pralidoxime Compounds; Time Factors; Trimedoxime

Biosensors based on acetyl cholinesterase (AChE) inhibition have been known for monitoring of pesticides in food and water samples. However, strong inhibition of the enzyme is a major drawback in practical application of the biosensor which can be overcome by reactivation of the enzyme for repeated use. In the present study, enzyme reactivation by oximes was explored for this purpose. Two oximes viz., 1,1'-trimethylene bis 4-formylpyridinium bromide dioxime (TMB-4) and pyridine 2-aldoxime methiodide (2-PAM) were compared for the reactivation of the immobilized AChE. TMB-4 was found to be a more efficient reactivator under repeated use, retaining more than 60% of initial activity after 11 reuses, whereas in the case of 2-PAM, the activity retention dropped to less than 50% after only 6 reuses. Investigations also showed that reactivation must be effected within 10 min after each analysis to eliminate the ageing effect, which reduces the efficiency of reactivation.

Topics: Acetylcholinesterase; Biosensing Techniques; Cholinesterase Inhibitors; Cholinesterase Reactivators; Enzymes, Immobilized; Insecticides; Paraoxon; Pralidoxime Compounds; Time Factors; Trimedoxime

The effects of possible activators of soluble guanylate cyclase were studied. Hydroxylamine and some oxime derivatives such as pyridinium aldoximes and bispyridinium dioxime (dipyroxime) were tested as possible guanylate cyclase activators. These compounds are known to be reactivators of choline esterase which has been preinhibited with phosphoorganic compounds. All the tested compounds were found to activate human platelet guanylate cyclase in the concentration range 10-6-10-3 M. The highest stimulatory affect was achieved at 10-4 M with hydroxylamine and dipyroxime: 210 +/- 10 and 320 +/- 15%, respectively. Potassium ferricyanide oxidation of these compounds under mild conditions formed nitroprusside ion, as registered by the electrochemical (polarographic) method; this is evidence that these compounds are NO donors. It is concluded that the activation of guanylate cyclase by the tested compounds is associated with their ability to generate NO during their biotransformation. The possible role of guanylate cyclase activation by oxime derivatives in the mechanism underlying the reactivation of inhibited choline esterase at the cell level is discussed.

Topics: Blood Platelets; Cholinesterase Reactivators; Cholinesterases; Guanylate Cyclase; Humans; Hydroxylamine; In Vitro Techniques; Nitric Oxide; Organophosphorus Compounds; Oximes; Pralidoxime Compounds; Trimedoxime

It has recently been shown that oximes can amplify the ability of cholinesterases to scavenge organophosphorus (OP) agents. Since both OP agents and oximes can disrupt performance, behavioral evaluation of bioscavenger therapies using oximes can be hindered. Therefore, we investigated the ability of three oximes, administered alone, to disrupt performance. The effects of trimedoxime bromide (TMB-4) (3.16-56.2 mg/kg), pralidoxime chloride (2-PAM) (10.0-237.1 mg/kg), and, 1-([[4-amincarbonyl)pyridino]-methoxy]-methyl)-2, 4-bis[(hydroxyimino)methyl] pyridinium dichloride monohydrate (HI-6) (10.0-237.1 mg/kg) were evaluated in rats using a variable-interval 56 (VI 56) s schedule of food reinforcement. Under control conditions, the VI 56 s schedule produced a constant rate of responding (i.e., lever-pressing). All three oximes produced dose-dependent decreases in responding, and the largest doses of TMB-4 and 2-PAM produced complete or nearly complete suppression of responding in all rats. Only the largest dose of HI-6 suppressed responding. Analysis of the dose-effect functions demonstrated that TMB-4 was substantially more potent than 2-PAM, which was slightly more potent than HI-6, for producing response suppression. These results establish doses of each oxime that will not contribute to disruption of responding, and thus, facilitate future evaluation of bioscavenger therapies against OP toxicity.

Topics: Animals; Behavior, Animal; Cholinesterase Inhibitors; Conditioning, Operant; Dose-Response Relationship, Drug; Male; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Rats; Rats, Sprague-Dawley; Reinforcement Schedule; Trimedoxime

This study summarizes the results of examination of acute oral toxicity of 26 organophosphorus insecticides in rats. The effectiveness of trimedoxime, obidoxime, pralidoxime and HI-6, given with atropine and diazepam, was tested in the treatment of poisoning with 2 LD50 of the insecticides. It was shown that the oximes were potent antidotes in poisoning with phosphate insecticides. Obidoxime, pralidoxime and HI-6 had low effectiveness in the treatment of poisoning with phosphonates and phosphorothiolates. However, none of the oximes was an effective antidote in poisoning with dimethoate and pyridafenthion. Trimedoxime was the most effective oxime in the treatment of insecticide poisoning, being successful especially at the lowest tested doses.

Topics: Administration, Oral; Animals; Antidotes; Atropine; Diazepam; Dose-Response Relationship, Drug; Insecticides; Male; Obidoxime Chloride; Organophosphorus Compounds; Oximes; Pralidoxime Compounds; Rats; Rats, Wistar; Trimedoxime

Two new series of asymetrically substituted 3,3'-bis-pyridinium monooximes bridged by oxopropane and propane groups were synthesized and characterized by spectral data and acid dissociation constants (pKas). Both the in vitro reactivation potency, in experiments with lyophilized electric eel acetylcholinesterase (AChE) inhibited by diisopropylfluorophosphate, and in vivo protection efficacy against diisopropylfluorophosphate intoxication in mice of these compounds were evaluated and compared with those of trimedoxime and 2-pyridine-aldoxime methiodide. The compounds were also evaluated for in vitro inhibition of AChE. The compounds with the oxopropane link were stronger inhibitors and weaker reactivators than the corresponding propane derivatives. No significant correlation was observed among pKa, oxime inhibition of AChE, reactivation of inhibited AChE, and protection index. Changing substituents in pyridine rings or altering linking groups between pyridine rings did not improve antidotal efficacy compared with trimedoxime and 2-pyridine-aldoxime methiodide.

Topics: Animals; Antidotes; Atropine; Cholinesterase Reactivators; Isoflurophate; Kinetics; Magnetic Resonance Spectroscopy; Mice; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Spectrophotometry, Infrared; Structure-Activity Relationship; Trimedoxime

The administration of 2-pyridine aldoxime methyl chloride (2-PAM Cl) is a standard part of the regimen for treatment of human overexposure to many organophosphorus pesticides and nerve agents. However, some literature references indicate that poisoning by carbaryl (1-naphthyl N-methyl carbamate), an insecticide in everyday use, is aggravated by the administration of 2-PAM Cl. This effect has been reported in the mouse, rat, dog and man. We have found that the inhibition of both eel acetylcholinesterase (eel AChE, EC 3.1.1.7) and human serum cholinesterase (human BuChE, EC 3.1.1.8) by carbaryl was enhanced by several oximes. Based on 95% confidence limits the rank order of potentiation with eel AChE was TMB-4 = Toxogonin > HS-6 = HI-6 > 2-PAM Cl. By the same criterion, the rank order of potentiation with human BuChE was TMB-4 > Toxogonin > HS-6 = 2-PAM Cl. Carbaryl-challenged mice also reflected a potentiation since TMB-4 exacerbated the toxicity more than 2-PAM Cl. Our hypothesis is that certain oximes act as allosteric effectors of cholinesterases in carbaryl poisoning, resulting in enhanced inhibition rates and potentiation of carbaryl toxicity.

Topics: Animals; Carbaryl; Cholinesterase Inhibitors; Cholinesterase Reactivators; Cholinesterases; Drug Synergism; Eels; Humans; Male; Mice; Oximes; Pralidoxime Compounds; Trimedoxime

1. The dispositions of the acetylcholinesterase reactivators: 2PAM-I, TMB4 and R665, labelled with 14C on the oxime group, have been studied in normal rats and rats poisoned by the organophosphates Soman and A4. 2. For all three compounds, radioactivity was eliminated mostly in the urine (60-90% dose in 24 h). Faecal elimination was low (5.8-17.2% in 72 h). 3. All three compounds concentrated in kidney, but only 2PAM-I and R665 concentrated in liver. TMB4 and R665 concentrated in mucopolysaccharide-containing tissues such as cartilage and intervertebral disc. Other tissues were weakly and uniformly labelled. Soman poisoning does not modify the kinetic parameters of both compounds, but A4 poisoning increases 2PAM-I tissue concentration. 4. Chromatography of urine and plasma showed only unchanged 2PAM-I, TMB4 and R665 in both healthy and poisoned animals. Despite the high concentration of 2PAM-I and R665 in liver, these oximes are not metabolized.

Topics: Acetylcholinesterase; Animals; Carbon Radioisotopes; Cholinesterase Reactivators; Male; Organophosphate Poisoning; Oximes; Poisoning; Pralidoxime Compounds; Rats; Rats, Inbred Strains; Tissue Distribution; Trimedoxime

Topics: Acetylcholinesterase; Animals; Brain; Carbamates; Cattle; Erythrocytes; Humans; Oximes; Pralidoxime Compounds; Pyridinium Compounds; Rabbits; Trimedoxime

Atropine, in combination with 1 of 6 other drugs, was tested in mice for the ability to prevent death by an otherwise lethal dose of the cholinesterase inhibitor, physostigmine. The atropine dose (4 mg/kg, i.p.) was kept constant, while the dose of the other drug in the pair was tested in 5 geometrically spaced doses, ranging down to 1/16 of the maximum dose (which caused no gross behavioral signs). Atropine alone saved 20% of the mice. The combination of atropine and benactyzine saved 100% of the mice at all 5 doses of benactyzine; similar complete protection was afforded by the combination of atropine and the largest dose of an oxime, TMB4 (15 mg/kg). Over 80% survivals were achieved with the larger doses of atropine combinations involving hexamethonium, mecamylamine, and diazepam. No enhanced protection occurred with atropine combinations with the oxime, 2-PAM. The toxicity of the effective combinations, when used in high doses without physostigmine challenge, revealed that deaths occurred over a narrow range of doses of all combinations except atropine/diazepam. An additive toxic effect of atropine was suggested with its combinations with TMB4, mecamylamine, and diazepam, whereas no additive toxicity occurred with combinations involving hexamethonium or benactyzine (i.e., the LD50 of the combinations was about the same as for hexamethonium or benzactyzine alone). The combinations with the best therapeutic safety ratio were with diazepam (no deaths at a dose 10 times that which saved 100% of mice) and benactyzine (no deaths at a more than 50-fold dose).

Topics: Animals; Atropine; Benactyzine; Cholinesterase Reactivators; Diazepam; Drug Therapy, Combination; Ganglionic Blockers; Hexamethonium; Hexamethonium Compounds; Male; Mecamylamine; Mice; Physostigmine; Pralidoxime Compounds; Tranquilizing Agents; Trimedoxime

Topics: Animals; Cholinesterase Reactivators; Drug Interactions; Erythrocytes; In Vitro Techniques; Male; Obidoxime Chloride; Pralidoxime Compounds; Rats; Trimedoxime

Topics: Animals; Antidotes; Cholinesterases; Enzyme Activation; Enzyme Reactivators; Female; Isoflurophate; Obidoxime Chloride; Oximes; Pralidoxime Compounds; Rats; Trimedoxime

Topics: Armin; Atropine; Bromides; Hydroxylamines; Parasympathomimetics; Phosphates; Pralidoxime Compounds; Pyridines; Trimedoxime

Pralidoxime chloride (pyridine-2-aldoxime methochloride; Protopam Chloride) and 1,1'-trimethylenebis(4-hydroxyiminomethylpyridinium bromide) (TMB-4) antagonize the spasm of the isolated or intact small intestine of the rabbit caused by the anticholinesterase, echothiophate iodide (S-2-dimethylaminoethyl OO-diethyl phosphorothiolate methiodide; Phospholine Iodide). In vitro, both oximes also antagonize the spasm caused by acetylcholine. The quantitative relationships have been studied in comparison with the activity of atropine against echothiophate and acetylcholine. Echothiophate-treated intestine which is subjected to a concentration of oxime sufficient to cause 100% restoration of function (but not cholinesterase reactivation) will go back into spasm on washing out both drugs. Strips treated with a high concentration of oxime, sufficient to cause 100% reactivation of cholinesterase, exhibit normal control tone and motility after washing. It is concluded that pralidoxime and 1,1'-trimethylenebis(4-hydroxyiminomethylpyridinium bromide) have an anticholinergic action as well as the ability to reactivate cholinesterase and that this action plays a significant part in the initial recovery of function under the conditions of these experiments.

Topics: Animals; Atropine; Cholinesterase Inhibitors; Cholinesterase Reactivators; Echothiophate Iodide; Hydroxylamines; Intestine, Small; Intestines; Oximes; Parasympatholytics; Pralidoxime Compounds; Pyridines; Rabbits; Trimedoxime

Topics: Animals; Atropine; Cholinesterase Inhibitors; Dogs; Hydroxylamines; Phosphates; Pralidoxime Compounds; Pyridines; Sarin; Trimedoxime

Topics: Atropine; Bromides; Cholinesterase Inhibitors; Cyclopropanes; Hydroxylamines; Phosphates; Pralidoxime Compounds; Pyridines; Trimedoxime