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Anticholinergics AND poisoning [keywords]
- Discovery of subtype selective muscarinic receptor antagonists as alternatives to atropine using in silico pharmacophore modeling and virtual screening methods. [Journal Article]
- Bioorg Med Chem 2013 May 1; 21(9):2651-62.
Muscarinic acetylcholine receptors (mAChRs) have five known subtypes which are widely distributed in both the peripheral and central nervous system for regulation of a variety of cholinergic functions. Atropine is a well known muscarinic subtype non-specific antagonist that competitively inhibits acetylcholine (ACh) at postganglionic muscarinic sites. Atropine is used to treat organophosphate (OP) poisoning and resulting seizures in the warfighter because it competitively inhibits acetylcholine (ACh) at the muscarinic cholinergic receptors. ACh accumulates due to OP inhibition of acetylcholinesterase (AChE), the enzyme that hydrolyzes ACh. However, atropine produces several unwanted side-effects including dilated pupils, blurred vision, light sensitivity, and dry mouth. To overcome these side-effects, our goal was to find an alternative to atropine that emphasizes M1 (seizure prevention) antagonism but has minimum M2 (cardiac) and M3 (e.g., eye) antagonism so that an effective less toxic medical countermeasure may be developed to protect the warfighter against OP and other chemical warfare agents (CWAs). We adopted an in silico pharmacophore modeling strategy to develop features that are characteristics of known M1 subtype-selective compounds and used the model to identify several antagonists by screening an in-house (WRAIR-CIS) compound database. The generated model for the M1 selectivity was found to contain two hydrogen bond acceptors, one aliphatic hydrophobic, and one ring aromatic feature distributed in a 3D space. From an initial identification of about five hundred compounds, 173 compounds were selected through principal component and cluster analyses and in silico ADME/Toxicity evaluations. Next, these selected compounds were evaluated in a subtype-selective in vitro radioligand binding assay. Twenty eight of the compounds showed antimuscarinic activity. Nine compounds showed specificity for M1 receptors and low specificity for M3 receptors. The pKi values of the compounds range from 4.5 to 8.5nM in comparison to a value of 8.7nM for atropine. 2-(diethylamino)ethyl 2,2-diphenylpropanoate (ZW62841) was found have the best desired selectivity. None of the newly found compounds were previously reported to exhibit antimuscarinic specificity. Both theoretical and experimental results are presented.
- [Urticaria multiforme is a variation of urticaria, which imitates erythema multiforme]. [Case Reports, English Abstract]
- Ugeskr Laeger 2013 Feb 11; 175(7):436-7.
A 21-month-old boy developed urticaria multiforme during the course of a presumed pneumonia, which was treated with imacillin. At admission to hospital he was initially considered to have erythema multiforme, but the correct diagnosis was soon established as urticaria multiforme. He had a good response to antihistamines. The diagnostic differences between urticaria multiforme and erythema multiforme are presented in this case report.
- Phase II study of magnesium sulfate in acute organophosphate pesticide poisoning. [Clinical Trial, Phase II, Comparative Study, Journal Article, Randomized Controlled Trial, Research Support, Non-U.S. Gov't]
- Clin Toxicol (Phila) 2013 Jan; 51(1):35-40.
Acute organophosphorus (OP) poisoning is relatively common and a major cause of death from poisoning in developing countries. Magnesium has been shown to be of benefit in animal models.We conducted a phase II study of bolus doses of (MgSO4) in 50 patients with acute organophosphate poisoning. Patients eligible for inclusion had ingested OP and had cholinergic symptoms consistent with moderate or severe poisoning. All patients received standard care of atropinization titrated to control muscarinic symptoms and pralidoxime. The trial was run in 4 sequential groups of patients. Participants in each group received a different total dose of MgSO4 (20%) administered as intermittent bolus doses infused over 10-15 min or placebo. There was one control patient for every 4 patients who received MgSO4. Group A (16 patients) received a total of 4 gm MgSO4 as a single bolus, group B (8 patients) received 8 gm (in two 4 gm doses q4H), group C (8 patients) received 12 gm (in three 4 gm doses q4H) group D (8 patients) received 16 gm (in four 4 gm doses q4H) and control (10 patients) received placebo). Patients were closely monitored for any adverse reaction like significant clinical neuromuscular disturbance and respiratory depression.No adverse reactions to magnesium were observed. The 24 hour urinary magnesium concentration were statistically different between 16 gm (234.74 ± 74.18 mg/dl) and control (118.06 ± 30.76 mg/dl) (p = 0.019), while it was much lower than the 80% of the intravenous magnesium load. Six patients died in control group compared to 3 in 4 gm, 2 in 8 gm and 1 in 12 gm group. There was no mortality in 16 gm group.Magnesium was well tolerated in this study. Larger studies are required to examine for efficacy.
- Acetaminophen/diphenhydramine overdose in profound hypothermia. [Case Reports, Journal Article]
- Clin Toxicol (Phila) 2013 Jan; 51(1):50-3.
There are few reports of acetaminophen overdose in hypothermic patients and even fewer reports describing profound hypothermia. The kinetics, risk of hepatotoxicity, and the possible dose adjustments to N-acetylcysteine (NAC) therapy are not known in this setting.A 37-year-old female was found unconscious outside in December and was brought by ambulance to a tertiary care Emergency Department (ED) following a presumed overdose of acetaminophen and diphenhydramine. She later confirmed the ingestion and reported the ingestion had occurred approximately 18 hours prior to being found. On arrival, she was profoundly hypothermic, with a core rectal temperature of 17°C. Her initial serum acetaminophen concentration was 232 mcg/mL 19 hours post ingestion of a reported dose of approximately 50 grams of acetaminophen and 2.5 grams of diphenhydramine. Active rewarming was started immediately and IV NAC was initiated using the standard treatment protocol. The patient did not develop serious signs of hepatic injury or NAC toxicity. The patient's AST and ALT peaked 12 hours after admission at 84 IU/L (ref 10-37 U/L) and 104 IU/L (ref 12-78 U/L), respectively. Her INR peaked 2 hours after admission at 1.46 (ref < 1.2).Despite the significant ingestion of acetaminophen, delayed presentation, prolonged period of decreased responsiveness, and profound hypothermia, the patient did not develop any signs/symptoms of liver injury. NAC was administered in a standard dose during her rewarming period without apparent toxicity. The patient's absorption and/or metabolism of acetaminophen were likely slowed by her hypothermia and possibly by the anticholinergic coingestant. Initiation of IV NAC at a standard dose was apparently safe and effective in preventing hepatotoxicity as the patient was rewarmed.Profound hypothermia may be protective of hepatic injury in acetaminophen overdose. Delayed absorption from the coingestant, diphenhydramine, may also have played a role. IV NAC was given in a standard dose without apparent toxicity in the setting of profound hypothermia. Lastly, IV NAC, in standard dosing, appeared to be effective in preventing hepatotoxicity during rewarming in a patient with a potentially hepatotoxic concentration of acetaminophen with a coingestion of the anticholinergic agent, diphenhydramine.
- The summary on non-reactivation cholinergic properties of oxime reactivators: the interaction with muscarinic and nicotinic receptors. [Journal Article, Research Support, Non-U.S. Gov't]
- Arch Toxicol 2013 Apr; 87(4):711-9.
Organophosphorus inhibitors (OP) of acetylcholinesterase (AChE) represent a group of highly toxic compounds. The treatment of OP intoxication is, however, insufficiently ensured. Currently, two main categories of drugs-anticholinergics and oxime reactivators- are employed as antidotes. Oximes have been reported to act at several levels of the cholinergic transmission, and among the non-reactivation effects, the interaction with cholinergic receptors stands out. This review addresses issues correlated with non-reactivating effects of oxime reactivators with a special focus on the muscarinic and nicotinic receptors, but involvement of other cholinergic structures such as AChE and choline uptake carriers are discussed too. It can be concluded that the oxime reactivators show a variation in their antagonistic effect on the muscarinic and nicotinic receptors, which is likely to be of significance in the treatment of OP poisoning. In vitro data reported oximes to exert higher efficacy on the muscarinic M2 subtype than on the AChE. However, this effect seemed to be subtype specific since the antagonistic M3 effect was lower. Also, and importantly, the antimuscarinic effect was larger than that on nicotinic receptors. Even though atropine showed a much higher muscarinic antagonism, it is supposed that non-reactivation properties of oxime reactivators play a significant role in the treatment of OP poisoning.
- Penehyclidine hydrochloride: a potential drug for treating COPD by attenuating Toll-like receptors. [Journal Article, Research Support, Non-U.S. Gov't, Review]
- Drug Des Devel Ther 2012.:317-22.
The aim of this review was to evaluate and summarize the available scientific information on penehyclidine hydrochloride (PHC) for the treatment of chronic obstructive pulmonary disease (COPD) as a result of its ability to attenuate Toll-like receptors. Penehyclidine hydrochloride is an anticholinergic drug manufactured in China, with both antimuscarinic and antinicotinic activity. PHC is used widely in the clinic as a reversal agent in cases of organic phosphorus poisoning and soman poisoning, but also may also have an important role as a bronchodilator in the treatment of obstructive airway disease, including asthma and, in particular, COPD.Our bibliographic sources included the CAPLUS, MEDLINE, REGISTRY, CASREACT, CHEMLIST, CHEMCATS, and CNKI databases, updated to September 2012. In order to assess the data in detail, we used the search terms "penehyclidine hydrochloride," "COPD," "muscarinic receptor," and "toll-like receptors." Papers were restricted to those published in the English and Chinese languages, and to "paper" and "review" as the document type. Patents were also reviewed.Our survey mainly yielded the results of research on PHC and the mechanisms of COPD. COPD is a preventable and treatable disease with some significant extrapulmonary manifestations that may contribute to its severity in some patients. Recently, it has been shown that muscarinic receptors may interact with Toll-like receptors. Basic and clinical studies of the relationship between the mechanism of action and the effects of PHC in the respiratory tract have been studied by a number of laboratories and institutions. The main advantages of PHC are that it has few M(2) receptor-associated cardiovascular side effects and attenuates Toll-like receptors.PHC may be a promising candidate agent in the treatment of COPD in the future because of its ability to attenuate Toll-like receptors. This review should be of help to those intending to research this topic further.
- Efficacy of the GluK1/AMPA receptor antagonist LY293558 against seizures and neuropathology in a soman-exposure model without pretreatment and its pharmacokinetics after intramuscular administration. [Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, Non-P.H.S.]
- J Pharmacol Exp Ther 2013 Jan; 344(1):133-40.
Control of brain seizures after exposure to nerve agents is imperative for the prevention of brain damage and death. Animal models of nerve agent exposure make use of pretreatments, or medication administered within 1 minute after exposure, in order to prevent rapid death from peripheral toxic effects and respiratory failure, which then allows the testing of anticonvulsant compounds. However, in a real-case scenario of an unexpected attack with nerve agents, pretreatment would not be possible, and medical assistance may not be available immediately. To determine if control of seizures and survival are still possible without pretreatment or immediate pharmacologic intervention, we studied the anticonvulsant efficacy of the GluK1 (GluR5)/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist (3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl]decahydroisoquinoline-3-carboxylic acid (LY293558) in rats that did not receive any treatment until 20 minutes after exposure to the nerve agent soman. We injected LY293558 intramuscularly, as this would be the most likely route of administration to humans. LY293558 (15 mg/kg), injected along with atropine and the oxime HI-6 at 20 minutes after soman exposure, stopped seizures and increased survival rate from 64% to 100%. LY293558 also prevented neuronal loss in the amygdala and hippocampus, and reduced neurodegeneration in a number of brain regions studied 7 days after soman exposure. Analysis of the LY293558 pharmacokinetics after intramuscular administration showed that this compound readily crosses the blood-brain barrier. There was good correspondence between the time course of seizure suppression by LY293558 and the brain levels of the compound.
- Recurrent neonatal organophoshorus poisoning. [Case Reports, Journal Article]
- Indian Pediatr 2012 Sep; 49(9):752-3.
Organophosphorus poisoning in neonates is extremely rare and needs high index of suspicion to diagnose it. The clinical presentation is often confused with the features of sepsis like apnea, copious oral secretions, diarrhea, letharginess, seizures. There may be recurrence of manifestations due to chronic exposure. We report a classic case admitted in the intensive care unit of our hospital.
- Toxidromes. [Journal Article, Review]
- Crit Care Clin 2012 Oct; 28(4):479-98.
The critical care physician is often called to care for poisoned patients. This article reviews the general approach to the poisoned patient, specifically focusing on the utility of the toxidrome. A toxidrome is a constellation of findings, either from the physical examination or from ancillary testing, which may result from any poison. There are numerous toxidromes defined in the medical literature. This article focuses on the more common toxidromes described in clinical toxicology. Although these toxidromes can aid the clinician in narrowing the differential diagnosis, care must be exercised to realize the exceptions and limitations associated with each.
- Use of physostigmine for cyclopentolate overdose in an infant. [Case Reports, Journal Article]
- Pediatrics 2012 Sep; 130(3):e703-5.
Topical application of eye drops may cause mild or severe adverse ocular or systemic effects. Children, particularly infants, are more prone to systemic adverse effects of topical eye drops because of their lower body mass and blood volume, immature metabolism, and immaturity of excretory, nervous, and cardiovascular systems. Early recognition of signs and symptoms of systemic toxicity is very important. Most of the signs and symptoms can resolve spontaneously; however, in severe cases, physostigmine treatment may be required. Respiratory distress is a rare adverse effect of cyclopentolate. We report an infant who developed respiratory distress after ocular instillation of cyclopentolate and was successfully treated with physostigmine. The benefit of physostigmine use with close follow-up should be borne in mind in cases with a life-threatening cyclopentolate adverse effect.