Effects Of Physostigmine Research Articles

Physostigmine reversal of delirium from second generation antipsychotic exposure: a retrospective cohort study from a regional poison center

Introduction Physostigmine is an effective antidote for antimuscarinic delirium. There is little evidence for its use to reverse delirium following second generation antipsychotic exposure. The purpose of this study is to describe the safety and effectiveness of physostigmine in reversing delirium from second generation antipsychotic exposure. Methods This is a retrospective cohort study of all patients reported to a single regional poison center treated with physostigmine following a second generation antipsychotic exposure from January 1, 2000 to April 15, 2021. The poison center electronic medical record was queried to identify cases and for data abstraction. The primary outcome was the positive response rate to physostigmine, as determined by two trained abstractors. Secondary outcomes included physostigmine dosing, and adverse events. Results Of 147 charts reviewed, 138 individual patients were included, and the response to physostigmine was reported in 128 patients. The most common second-generation antipsychotic exposure was quetiapine (97; 70.3 percent). A positive response to physostigmine was noted in 106/128 (82.8 percent) patients [95 percent confidence interval 68.9–83.6 percent]. Median number of physostigmine doses was 1 (interquartile range 1–3; range 1–9). The median total physostigmine dose received was 2 mg (interquartile range 2–6 mg; range 0.15–30 mg). The positive physostigmine response rate for patients with an antimuscarinic co-ingestion was not significantly different compared to patients with a different co-ingestion or no co-ingestion (25/34 versus 81/94; P = 0.09). Adverse events were reported in four (2.9 percent) patients, including one death. Discussion A positive response to physostigmine to treat antimuscarinic delirium from second generation antipsychotic exposure was reported in 82.8 percent of patients, which is similar to previous physostigmine studies. Adverse events were infrequent, and included diaphoresis (one 0.7 percent), seizure (one; 0.7 percent), and bradycardia (one; 0.7 percent). One (0.7%) patient suffered a cardiac arrest 60 minutes after receiving physostigmine to treat antimuscarinic delirium following having received increasing clozapine doses over the previous month. Conclusions In this study, physostigmine appears to be a safe and effective treatment for antimuscarinic delirium from second generation antipsychotic exposure. Further studies are needed to validate the safety and effectiveness of physostigmine for this indication.

Hippocampal acetylcholine modulates stress-related behaviors independent of specific cholinergic inputs.

Acetylcholine (ACh) levels are elevated in actively depressed subjects. Conversely, antagonism of either nicotinic or muscarinic ACh receptors can have antidepressant effects in humans and decrease stress-relevant behaviors in rodents. Consistent with a role for ACh in mediating maladaptive responses to stress, brain ACh levels increase in response to stressful challenges, whereas systemically blocking acetylcholinesterase (AChE, the primary ACh degradative enzyme) elicits depression-like symptoms in human subjects, and selectively blocking AChE in the hippocampus increases relevant behaviors in rodents. We used an ACh sensor to characterize stress-evoked ACh release, then used chemogenetic, optogenetic and pharmacological approaches to determine whether cholinergic inputs from the medial septum/diagonal bands of Broca (MSDBB) or ChAT-positive neurons intrinsic to the hippocampus mediate stress-relevant behaviors in mice. Chemogenetic inhibition or activation of MSDBB cholinergic neurons did not result in significant behavioral effects, while inhibition attenuated the behavioral effects of physostigmine. In contrast, optogenetic stimulation of septohippocampal terminals or selective chemogenetic activation of ChAT-positive inputs to hippocampus increased stress-related behaviors. Finally, stimulation of sparse ChAT-positive hippocampal neurons increased stress-related behaviors in one ChAT-Cre line, which were attenuated by local infusion of cholinergic antagonists. These studies suggest that ACh signaling results in maladaptive behavioral responses to stress if the balance of signaling is shifted toward increased hippocampal engagement.

The role of N-cholinoreceptors in somatovisceral intersystemic interactions in early rat ontogenesis

Interaction of slow-wave rhythmic components of cardiac, respiratory and motor activities was analyzed in non-narcotized of newborn 1-day-old (P1) and 16-day-old (P16) Wistar rat pups under normal and impaired cholinergic regulation. Functional activity of these three systems is rhythmic, and coordination of their functioning is an important element of the mechanism of adaptive rearrangements under changing factors of the external and internal environment. The acetylcholinesterase inhibitor physostigmine (eserine) was used to increase the level of endogenous acetylcholine and enhance cholinergic effects. To reveal the role of N-cholinoreceptors in intersystemic somatovisceral interactions (ISI), we performed blockade of this receptor type with benzohexonium. Administration of physostigmine leads to the development of a number of pathological reactions and a decrease in the level of ISI in all ranges of modulating rhythms in rats of both ages. ISI in younger rats appear to be more resistant to changes in the level of cholinergic activation. Blockade of N-cholinoreceptors causes inhibition of ISI at P1 and partially to their potentialization at P16. The activation of cholinoreactive structures, which occurred against the background of cholinoreceptors blockade, reduces the pathological effects of physostigmine in animals of both ages, but at the same time leads to an attenuation of ISI. This weakening is more pronounced in 16-day old rats, which may indicate the formation of the definitive level of cholinergic regulation in the first weeks of postnatal ontogenesis.

Pharmacological support to anti-arthritic prospective of physostigmine: a new approach.

Rheumatoid arthritis (RA) is a slowly progressing inflammatory autoimmune disease. Several features are involved in the RA pathogenesis in addition to environmental and genetic factors. Previously it has been reported that acetyl cholinesterase (AChE) activity is enhanced in old age and may contribute in the progression of RA. The current experimental work was projected to assess the activity of physostigmine (a cholinesterase inhibitor) for treatment of RA. In vitro and in vivo approaches were used for such evaluation. However, enzyme linked immunosorbent assays (ELISA) was performed to determine the concentrations of Prostaglandins E2 (PGE2) and tumor necrosis factor-α in arthritic rats after treatment with physostigmine. Moreover, anti-oxidant assays were employed to calculate the level of super oxide dismutase (SOD) and catalase peroxidase (CAT) in tissue of treated animals. The results claimed the dose dependent protective and stabilizing effect of physostigmine on denaturation of albumin (egg and bovine serum) protein and human red blood cell membrane, respectively, through in vitro studies. Furthermore, the physostigmine (10 and 20mg/kg) significantly (p < 0.001) reduced the swelling of paw after induction of arthritis with formaldehyde or complete Freund's adjuvant (CFA) as compared to arthritic control animals. Moreover, significant (p < 0.001) reduction in the levels of inflammatory markers (PGE2 and TNF-α) at doses of 10 and 20mg/kg of physostigmine has been observed in ELISA test. Likewise, there was a prominent rise in levels of SOD and CAT in animals treated with physostigmine. These findings pharmacologically conclude the anti-arthritic effect of physostigmine.

Effect of physostigmine on recovery from septic shock following intra-abdominal infection – Results from a randomized, double-blind, placebo-controlled, monocentric pilot trial (Anticholium® per Se)

PurposeThe cholinergic anti-inflammatory pathway has been shown to be accessible by physostigmine salicylate in animal models. However, the cholinesterase inhibitor is not approved for adjunctive therapy in sepsis, and tolerability and safety of high initial doses followed by continuous infusion have not been investigated. Materials and methodsIn this trial, 20 patients with perioperative septic shock due to intra-abdominal infection were eligible. The physostigmine group received an initial dose of 0.04 mg/kg physostigmine salicylate, followed by continuous infusion of 1 mg/h for 120 h; the placebo group was treated with 0.9% sodium chloride. Primary outcome was the mean Sequential Organ Failure Assessment (SOFA) score during treatment and up to 14 days. ResultsAdministration of physostigmine salicylate was well tolerated. Mean SOFA scores were 8.9 ± 2.5 and 11.3 ± 3.6 (mean ± SD) for physostigmine and placebo group, respectively. Adjusted for age, difference between means was not statistically significant (−2.37, 95% CI: −5.43 to 0.70, p = 0.121). Norepinephrine doses required only appeared lower in the physostigmine group (p = 0.064), along with a more rapid reduction from an elevated heart rate possibly indicating less hemodynamic instability. ConclusionsTreatment with physostigmine salicylate was feasible and safe. Further studies are justified to assess the effect on recovery from septic shock. Trial registrationEudraCT Number 2012-001650-26, ClinicalTrials.gov identifier NCT03013322.

Adverse Effects of Physostigmine.

Physostigmine is a tertiary amine carbamate acetylcholinesterase inhibitor. Its ability to cross the blood-brain barrier makes it an effective antidote to reverse anticholinergic delirium. Physostigmine is underutilized following the publication of patients with sudden cardiac arrest after physostigmine administration in patients with tricyclic antidepressant (TCA) overdoses. We completed a narrative literature review to identify reported adverse effects associated with physostigmine administration. One hundred sixty-one articles and a total of 2299 patients were included. Adverse effects occurred in 415 (18.1%) patients. Hypersalivation (206; 9.0%) and nausea and vomiting (96; 4.2%) were the most common adverse effects. Fifteen (0.61%) patients had seizures, all of which were self-limited or treated successfully without complication. Symptomatic bradycardia occurred in 8 (0.35%) patients including 3 patients with bradyasystolic arrests. Ventricular fibrillation occurred in one (0.04%) patient with underlying coronary artery disease. Of the 394 patients with TCA overdose, adverse effects were described in 14 (3.6%). Adverse effects occurred in 7.7% of patients treated with an overdose of an anticholinergic agent compared with 20.6% of patients with non-anticholinergic agents. Five (0.22%) fatalities were identified. In conclusion, significant adverse effects associated with the use of physostigmine were infrequently reported. Seizures were self-limited or resolved with benzodiazepines, and all patients recovered neurologically intact. Physostigmine should be avoided in patients with QRS prolongation on EKG, and caution should be used in patients with a history of coronary artery disease and overdoses with QRS prolonging medications. Based upon our review, physostigmine is a safe antidote to treat anticholinergic overdose.

Datura and Brugmansia plants related antimuscarinic toxicity: an analysis of poisoning cases reported to the Taiwan poison control center

Introduction: Datura and Brugmansia plants, especially Datura species, have been used for their hallucinogenic effects in the United States and Europe; whereas Datura plants have been used as a traditional medicine in many Asian countries. This study was conducted to better understand the pattern and outcome of Datura/Brugmansia plant related poisoning in Taiwan.Methods: This is a retrospective case series study of all cases with Datura/Brugmansia exposure reported to the Taiwan Poison Control Center between 1986 and 2015. Data for patients with relevant poisoning were reviewed and abstracted. Logistic regression analysis was used to identify potential predictors of the severity of poisoning; bivariate analysis was employed to assess the effectiveness of physostigmine in the treatment of Datura/Brugmansia poisoning.Results: A total of 203 cases involving 114 Datura exposures and 89 Brugmansia suaveolens exposures were eligible for analysis. Using Datura/Brugmansia for a medicinal purpose by the patients without consulting Chinese medicine practitioners was the most common reason of poisoning (81.2%); whereas only 2% of the patients were poisoned after medicinal use associated with the prescription from Chinese medicine practitioners. None of the 203 patients had used Datura/Brugmansia plant for recreational purpose. Most frequently observed clinical effect was mydriasis (53.2%), followed by confusion (40%), tachycardia (35.5%), dry mouth (35.5%), dizziness (34%), dry skin (32.5%), and delirium (31%). Seventy-three cases (36%) had severe effects; none of them died. Misidentification of the plants and ingestion of plant parts other than flowers were positively associated with the severity of poisoning. Forty patients (19.7%) received physostigmine therapy and patients receiving physostigmine had an earlier resolution of central nervous system toxicity than those who did not.Conclusions: Medicinal use without consulting Chinese medicine practitioners is the main reason for Datura/Brugmansia poisoning in Taiwan. Consumption of parts other than flowers and misidentification of the plants predicted the severity of poisoning in this study. Patients who received physostigmine appear to have earlier improvement in the central nervous system effects. No adverse events were reported from physostigmine administration.

Therapeutic effects of physostigmine during systemic inflammation.

IntroductionUsually, physostigmine is used as antidote for anticholinergic poisons in order to improve hemodynamics and cardiac output. In addition, it causes beneficial effects during sepsis when added timely. Here, we studied whether physostigmine improves hemodynamics when treatment during systemic inflammation was delayed.MethodsTwo series of randomized studies with overall 44 rats were conducted. Systemic inflammation was induced by lipopolysaccharide (LPS) infusion (0.5 mg LPS/kg×h). Physostigmine (PHY) was intravenously applied after an LPS infusion period of 90 minutes (50 µg PHY/kg within 10 minutes) with (series 1) and without (series 2) additional volume loading. Hemodynamic parameters, blood gases, and parameters for tissue damage were periodically determined for up to 180 minutes.ResultsEven though volume was additionally administered (series 1), LPS caused a reduction of peripheral blood flow. Treatment with PHY improved hemodynamics in macrocirculation (mean arterial blood pressure) and microcirculation (peripheral blood flow). PHY neither affected alterations in blood gases, electrolyte homeostasis, and glucose metabolism nor prevented intestinal damage induced by LPS. In series 2, without any additional volume loading, PHY likewise resulted in an improvement of the LPS-induced alterations in macro- and microcirculation, but finally worsened the LPS-mediated effects on plasma parameters for tissue damage such as creatine kinase, probably due to the lack of volume and a further damage to the heart.ConclusionThe present results demonstrated that hemodynamic responses to PHY may not only be visible in patients with anticholinergic drug overdose but also be visible in septic patients, provided that fluid intake of these patients is adequate.

Physostigmine-loaded liposomes for extended prophylaxis against nerve agent poisoning

Pre-administration of physostigmine can prevent poisoning against nerve agent exposure by reversibly binding to cholinesterase. However, its cholinesterase protection-based prophylactic effect can be eliminated rapidly due to short biological half-life. Liposomes are useful for encapsulating hydrophilic drugs like physostigmine, and can be used for sustained release after parenteral injection. Thus, physostigmine liposomes were prepared by the pH-gradient condition-based remote-loading method for subcutaneous injection. In addition, polyethylene glycol (PEG)-lipid was applied to further extend the release of physostigmine and its prophylactic action. In vitro release of physostigmine, pharmacokinetics and duration of prophylactic effect were then evaluated. Physostigmine was dissolved in distilled water and used as a solution group for comparison. The prepared liposomes showed spherical shape and their particle size was around 130 μm. Addition of PEG-lipid in liposomes significantly increased the entrapment efficiency of physostigmine. Both control and PEG liposomes exhibited sustained release pattern compared to the solution. Moreover, the release of PEG liposomes was relatively slower than that of the control liposomes. Pharmacokinetic study in rats revealed that physostigmine liposomes exhibited lower maximum plasma concentration and longer half-life compared to the solution. Plasma cholinesterase inhibition ratio in the liposomal group decreased more gradually compared to the solution. Moreover, PEG liposomes showed higher plasma concentration of physostigmine and cholinesterase inhibition ratio compared to the control liposomes. These results suggest that PEG liposomes have potential to enhance the duration of cholinesterase-protecting effect of physostigmine.

Safety and effectiveness of physostigmine: a 10-year retrospective review

Background: Physostigmine has long been recognized as an antidote to reverse anticholinergic delirium. However, its effectiveness, safety profile, and dosing have been disputed.Objectives: To describe effectiveness, adverse events, and dosing associated with the use of physostigmine to reverse anticholinergic delirium.Methods: A retrospective cohort study of hospitalized patients reported to a regional poison center system between 2003 and 2012 who received physostigmine to reverse an anticholinergic toxidrome. Data extraction of a priori defined variables were recorded with concurrence of investigators. The cases were stratified by the primary ingestant as the presumed causative agent and associations for response were performed using odds ratios (ORs), 95% confidence intervals (CI’s), and p values.Results: Of the 1422 cases identified, 191 met the inclusion criteria. Patients exposed to non-diphenhydramine antihistamines (n = 14), antipsychotics (n = 4), and tricyclic antidepressants (n = 3) had 100% response to physostigmine, whereas anticholinergic plants (n = 46/67; 68.7%, OR: 0.70; CI: 0.36–1.35), diphenhydramine (n = 43/56; 64.2%, OR: 1.30; CI: 0.63–2.68), and combination products (n = 8/10; 80%, OR: 1.48; CI: 0.30–7.24) had partial response rates. Of the included patients, 142 (74.3%) were treated with physostigmine alone, and 16 (8.4%) of these patients were discharged directly from the emergency department (ED).Discussion: Most patients, 182 (95.3%), had no documented adverse effects. Four patients (2.1%) experienced emesis, two experienced QTc prolongation (1.0%), and two experienced seizures (1.0%). There was a single fatality 6 h after physostigmine administration. Average initial total doses of physostigmine ranged from 1.0 to 1.75 mg. Most patients were admitted to the ICU (n = 110; 57.6%), however, 36 (18.8%) patients were discharged directly from the ED.Conclusions: In this retrospective cohort study, physostigmine administration to reverse anticholinergic delirium had a good safety profile, and often improved or resolved anticholinergic delirium when administered in doses less than 2 mg.

Determination of the Residues in the Extracellular Domain of the Nicotinic α Subunit Required for the Actions of Physostigmine on Neuronal Nicotinic Receptors.

Physostigmine can potentiate and inhibit neuronal nicotinic receptors, in addition to inhibiting the activity of acetylcholinesterase. We found that receptors containing three copies of the α2 subunit are inhibited by low concentrations of physostigmine in contrast to receptors containing three copies of the α4 subunit that are potentiated. We exploited this observation to determine the regions required for the actions of physostigmine. Chimeric constructs of the α2 and α4 subunits located two regions in the extracellular amino-terminal domain of the subunit: the E loop (a loop of the transmitter-binding domain) and a region closer to the amino-terminus that collectively could completely determine the different effects of physostigmine. Point mutations then identified a single residue, α2(I92) versus α4(R92), that, when combined with transfer of the E loop, could convert the inhibition seen with α2 subunits to potentiation and the potentiation seen with α4 subunits to inhibition. In addition, other point mutations could affect the extent of potentiation or inhibition, indicating that a more extensive set of interactions in the amino-terminal domain plays some role in the actions of physostigmine.

The E Loop of the Transmitter Binding Site Is a Key Determinant of the Modulatory Effects of Physostigmine on Neuronal Nicotinic α4β2 Receptors.

Physostigmine is a well known inhibitor of acetylcholinesterase, which can also activate, potentiate, and inhibit acetylcholine receptors, including neuronal nicotinic receptors comprising α4 and β2 subunits. We have found that the two stoichiometric forms of this receptor differ in the effects of physostigmine. The form containing three copies of α4 and two of β2 was potentiated at low concentrations of acetylcholine chloride (ACh) and physostigmine, whereas the form containing two copies of α4 and three of β2 was inhibited. Chimeric constructs of subunits indicated that the presence of inhibition or potentiation depended on the source of the extracellular ligand binding domain of the subunit. Further sets of chimeric constructs demonstrated that a portion of the ACh binding domain, the E loop, is a key determinant. Transferring the E loop from the β2 subunit to the α4 subunit resulted in strong inhibition, whereas the reciprocal transfer reduced inhibition. To control the number and position of the incorporated chimeric subunits, we expressed chimeric constructs with subunit dimers. Surprisingly, incorporation of a subunit with an altered E loop had similar effects whether it contributed either to an intersubunit interface containing a canonical ACh binding site or to an alternative interface. The observation that the α4 E loop is involved suggests that physostigmine interacts with regions of subunits that contribute to the ACh binding site, whereas the lack of interface specificity indicates that interaction with a particular ACh binding site is not the critical factor.

Physostigmine and Methylphenidate Induce Distinct Arousal States During Isoflurane General Anesthesia in Rats.

Although emergence from general anesthesia is clinically treated as a passive process driven by the pharmacokinetics of drug clearance, agents that hasten recovery from general anesthesia may be useful for treating delayed emergence, emergence delirium, and postoperative cognitive dysfunction. Activation of central monoaminergic neurotransmission with methylphenidate has been shown to induce reanimation (active emergence) from general anesthesia. Cholinergic neurons in the brainstem and basal forebrain are also known to promote arousal. The objective of this study was to test the hypothesis that physostigmine, a centrally acting cholinesterase inhibitor, induces reanimation from isoflurane anesthesia in adult rats. The dose-dependent effects of physostigmine on time to emergence from a standardized isoflurane general anesthetic were tested. It was then determined whether physostigmine restores righting during continuous isoflurane anesthesia. In a separate group of rats with implanted extradural electrodes, physostigmine was administered during continuous inhalation of 1.0% isoflurane, and the electroencephalogram changes were recorded. Finally, 2.0% isoflurane was used to induce burst suppression, and the effects of physostigmine and methylphenidate on burst suppression probability (BSP) were tested. Physostigmine delayed time to emergence from isoflurane anesthesia at doses ≥0.2 mg/kg (n = 9). During continuous isoflurane anesthesia (0.9% ± 0.1%), physostigmine did not restore righting (n = 9). Blocking the peripheral side effects of physostigmine with the coadministration of glycopyrrolate (a muscarinic antagonist that does not cross the blood-brain barrier) produced similar results (n = 9 each). However, during inhalation of 1.0% isoflurane, physostigmine shifted peak electroencephalogram power from δ (<4 Hz) to θ (4-8 Hz) in 6 of 6 rats. During continuous 2.0% isoflurane anesthesia, physostigmine induced large, statistically significant decreases in BSP in 6 of 6 rats, whereas methylphenidate did not. Unlike methylphenidate, physostigmine does not accelerate time to emergence from isoflurane anesthesia and does not restore righting during continuous isoflurane anesthesia. However, physostigmine consistently decreases BSP during deep isoflurane anesthesia, whereas methylphenidate does not. These findings suggest that activation of cholinergic neurotransmission during isoflurane anesthesia produces arousal states that are distinct from those induced by monoaminergic activation.

Reversal of cardiac vagal effects of physostigmine by adjunctive muscarinic blockade

Pre-treatment with reversible acetylcholinesterase (AChE) inhibitors is an effective strategy for reducing lethality following organophosphate nerve agent exposure. AChE inhibition may have unwanted cardiac side effects, which could be negated by adjunctive anti-cholinergic therapy. The aims of the present study were to examine the concentration-dependent effects of physostigmine on cardiac responses to vagus nerve stimulation (VNS), to test whether adjunctive treatment with hyoscine can reverse these effects and to assess the functional interaction and electrophysiological consequences of a combined pre-treatment. Studies were performed in an isolated innervated rabbit heart preparation. The reduction in heart rate with VNS was augmented by physostigmine (1–1000nmol/L), in a concentration-dependent manner – with an EC50 of 19nmol/L. Hyoscine was shown to be effective at blocking the cardiac responses to VNS with an IC50 of 11nmol/L. With concomitant perfusion of physostigmine, the concentration-response curve for hyoscine was shifted downward and to the right, increasing the concentration of hyoscine required to normalise (to control values) the effects of physostigmine on heart rate. At the lowest concentration of hyoscine examined (1nmol/L) a modest potentiation of heart rate response to VNS (+15±3%) was observed. We found no evidence of cardiac dysfunction or severe electrophysiological abnormalities with either physostigmine or hyoscine alone, or as a combined drug-therapy. The main finding of this study is that hyoscine, at concentrations greater than 10−8M, is effective at reversing the functional effects of physostigmine on the heart. However, low-concentrations of hyoscine may augment cardiac parasympathetic control.

Neuroinflammation: effect of surgical stress compared to anaesthesia and effect of physostigmine

Objectives: Surgical interventions can cause systemic postoperative inflammation, which in turn can induce neuroinflammation. A close link between immune reaction and cholinergic metabolism has been postulated. Pharmacological enhancement of cholinergic activity by administering physostigmine is known to induce protective effects. It is not known, however, whether physostigmine has an impact on postoperative inflammation and acetylcholine metabolism after a partial liver resection (PLR) surgery.Methods: Rats (n = 100) underwent a PLR or sham surgery. Rats were investigated before the intervention and 120 min and 24 h postoperatively. The control group only received sevoflurane anaesthesia. Half of each treatment group received a single intraoperative dose of physostigmine, whereas the others were given placebo.Acetylcholine (ACHE) and butyrylcholinesterase (BuCHE) activity and IL1β, IL6 and corticosterone levels were measured in rat plasma and brain. Acetylcholine (ACH) concentrations were determined additionally in cerebral tissue.Results: Surgical interventions induced a peripheral stress reaction, which was characterized by an increase (p < 0.05) in pro-inflammatory cytokines, cholinergic esterases and corticosterone at 120 min postoperatively in rat blood and in cerebral tissue. At 24 h postoperatively, all measured cerebral parameters reached control values. In blood, IL1β and BuCHE were still increased, suggesting they are peripheral markers of a stress reaction. The reduced cerebral acetylcholine is increased after physostigmine administration. Furthermore, physostigmine reduced IL1β (p < 0.05).Conclusion: We show in this observational study that a single intraoperative dose of physostigmine produced a sustained anti-inflammatory effect in rat blood and brain up to 120 min postoperatively, which was especially pronounced under the condition of PLR surgery.

Species- and concentration-dependent differences of acetyl- and butyrylcholinesterase sensitivity to physostigmine and neostigmine

Previous and more recent studies show that cholinesterase inhibitors (ChE-Is) are an important possibility for therapeutic intervention in Alzheimer's Disease, sepsis and other inflammatory syndromes. ChE-Is maintain high levels of acetylcholine (ACh) determining beneficial effects on the disease process. Despite numerous efforts to identify the appropriate choice of agents and dose of ChE-Is, a common protocol regarding concentration- and species-dependent differences in inhibitory potency (IC 50) of clinical relevant ChE-Is is still not available.To evaluate the in vitro sensitivity of Acetyl- and Butyrylcholinesterase (AChE, BChE), we compared the concentration-response effects of physostigmine and neostigmine on cholinesterases in whole blood from rat and human. A spectrophotometrical test system based on in vitro Ellman's reagent has been used to determine the kinetic properties of clinical relevant ChE-Is.In vitro, the enzyme activity of human AChE and BChE was inhibited in a concentration-dependent manner until a residual activity of 4–6% for AChE and 20–30% for BChE (IC 50 human AChE: 0.117 ± 0.007 μM physostigmine, 0.062 ± 0.003 μM neostigmine; IC 50 human BChE: 0.373 ± 0.089 μM neostigmine; 0.059 ± 0.012 μM physostigmine). The inhibition curve of rat BChE in contrast showed no concentration-dependency for physostigmine and neostigmine (87% residual activity even at high inhibitor concentrations). Rat AChE was inhibited in a concentration-dependent manner until a residual activity of 53%.The results suggest that cholinesterases from human and rat show marked species- and inhibitor-dependent differences in sensitivity to physostigmine and neostigmine. Knowledge of such differences may be critical in assessing the possible therapeutic effects of ChE-Is in both species and may guide researchers in the optimal design of future experiments regarding the application of ChE-Is.

Modeling bipolar disorder in mice by increasing acetylcholine or dopamine: chronic lithium treats most, but not all features.

Bipolar disorder (BD) is a disabling and life-threatening disease characterized by states of depression and mania. New and efficacious treatments have not been forthcoming partly due to a lack of well-validated models representing both facets of BD. We hypothesized that cholinergic- and dopaminergic-pharmacological manipulations would model depression and mania respectively, each attenuated by lithium treatment. C57BL/6 J mice received the acetylcholinesterase inhibitor physostigmine or saline before testing for "behavioral despair" (immobility) in the tail suspension test (TST) and forced swim test (FST). Physostigmine effects on exploration and sensorimotor gating were assessed using the cross-species behavioral pattern monitor (BPM) and prepulse inhibition (PPI) paradigms. Other C57BL/6 J mice received chronic lithium drinking water (300, 600, or 1200 mg/l) before assessing their effects alone in the BPM or with physostigmine on FST performance. Another group was tested with acute GBR12909 (dopamine transporter inhibitor) and chronic lithium (1000 mg/l) in the BPM. Physostigmine (0.03 mg/kg) increased immobility in the TST and FST without affecting activity, exploration, or PPI. Lithium (600 mg/l) resulted in low therapeutic serum concentrations and normalized the physostigmine-increased immobility in the FST. GBR12909 induced mania-like behavior in the BPM of which hyper-exploration was attenuated, though not reversed, after chronic lithium (1000 mg/ml). Increased cholinergic levels induced depression-like behavior and hyperdopaminergia induced mania-like behavior in mice, while chronic lithium treated some, but not all, facets of these effects. These data support a cholinergic-monoaminergic mechanism for modeling BD aspects and provide a way to assess novel therapeutics.

Acetylcholinesterase inhibitor modifications: a promising strategy to delay the progression of Alzheimer's disease.

Alzheimer's disease (AD), a fatal, progressive, neurodegenerative disorder, is the most common cause of old-age dementia, accounting for 50–75% of dementia patients. Early stages of AD are marked by vocabulary shrinkage, spatial disorientation, depression, apraxia, and deterioration of recent forms of declarative memory. In course of time, the patients require close supervision due to the loss of cognitive and functional abilities, and at the terminal stages of the disease, all forms of memory are severely impaired with the patients needing nursing home care (World Alzheimer Report, 2013).

Physostigmine is the Antidote for Anticholinergic Syndrome

Recently, we read the observation by Walker et al. [1] published in the Journal of Medical Toxicology and commend the authors for their recognition of anticholinergic syndrome. However, we are distressed that a 13-year-old pediatric patient was treated with a novel drug without first having received the known antidote for anticholinergic delirium, physostigmine. The statement “the currently recommended therapies for anticholinergic toxidrome are largely supportive” is inaccurate. Physostigmine has been recommended by a consensus panel for hospitals providing emergency care for treatment of anticholinergic syndrome [2]. If there is an available antidote, the standard of care should never be “largely supportive.” Treating the underlying cause of patients’ symptoms, rather than simply managing clinical situations is central to the practice of medicine. Between 2003 and 2010, our center treated nearly 1200 patients with physostigmine, 80 % of whom experienced neurobehavioral improvement with appropriately dosed antidote [3]. Adverse effects were minimal and primarily consisted of short-lived peripheral cholinergic effects. Physostigmine is available as an injection solution in 2 mg vials ($8.21) available for use as packaged. Dexmedetomidine requires mixing in a controlled environment; according to Micromedex, “dilute 200 mcg (2 mL, $65.28) with 48 ml of normal saline and then shake[n] gently to mix.” It is difficult to fathom that any pharmacy cannot readily provide physostigmine after its being ordered. The cost difference between dexmedetomidine and physostigmine is also significant. Physostigmine was discovered over a century ago with its targeted clinical effects well-documented since that time [4]; to choose a much newer drug without an indication for anticholinergic toxidrome represents clinician-driven experimentation. Was consent obtained from the parents before using this novel therapy? What would be the implications of an adverse event when the known antidote had not been used first? For this patient, we would have recommended 0.02 mg/kg physostigmine (range 0.5–2 mg) over 2 min using peripheral intravenous access. At 8–10 min, we would have instructed the administering clinician to reassess the neurologic exam (we typically use Riker Sedation Analgesia Score [5] or ask the patient for presidents in reverse order before and after physostigmine (or other age/developmental marker)) as a simple way to assess change in cognition. If improvement is noted, we place an order for repeating physostigmine q1 h prn. The adverse effects of physostigmine are cholinergic in nature and occur 10–20 min after administration, or when CNS peak effect occurs [6]. In our experience, with the dosing as recommended above, this would amount to diaphoresis, emesis, diarrhea, and/or urinary incontinence [7]. With proper intermittent, weight-based dosing, more robust cholinergic effects of bronchorrhea and bradycardia are not observed. Seizures are rare, and often cannot be attributed to the antidote use [3]. Cholinergic symptoms would not be anticipated in such as case as the one described due to the classical history and physical findings. When they do emerge in the absence of improvement in mentation, central anticholinergia is ruled out, and the therapy should be abandoned. In such a circumstance, adjunctive treatments for managing an undifferentiated toxicologic delirium might then logically be considered.

No evidence for role of extracellular choline-acetyltransferase in generation of gamma oscillations in rat hippocampal slices in vitro

Acetylcholine (ACh) is well known to induce persistent γ-oscillations in the hippocampus when applied together with physostigmine, an inhibitor of the ACh degrading enzyme acetylcholinesterase (AChE). Here we report that physostigmine alone can also dose-dependently induce γ-oscillations in rat hippocampal slices. We hypothesized that this effect was due to the presence of choline in the extracellular space and that this choline is taken up into cholinergic fibers where it is converted to ACh by the enzyme choline-acetyltransferase (ChAT). Release of ACh from cholinergic fibers in turn may then induce γ-oscillations. We therefore tested the effects of the choline uptake inhibitor hemicholinium-3 (HC-3) on persistent γ-oscillations either induced by physostigmine alone or by co-application of ACh and physostigmine. We found that HC-3 itself did not induce γ-oscillations and also did not prevent physostigmine-induced γ-oscillation while washout of physostigmine and ACh-induced γ-oscillations was accelerated. It was recently reported that ChAT might also be present in the extracellular space (Vijayaraghavan et al., 2013). Here we show that the effect of physostigmine was prevented by the ChAT inhibitor (2-benzoylethyl)-trimethylammonium iodide (BETA) which could indicate extracellular synthesis of ACh. However, when we tested for effects of extracellularly applied acetyl-CoA, a substrate of ChAT for synthesis of ACh, physostigmine-induced γ-oscillations were attenuated. Together, these findings do not support the idea that ACh can be synthesized by an extracellularly located ChAT.