Gastroretentive Delivery Approach to Address pH-Dependent Degradation of (+)- and (-)-Phenserine.

(-)-Phenserine ("phenserine") and (+)-phenserine (posiphen; buntanetap) are longer-acting enantiomeric analogs of physostigmine with demonstrated promise in the treatment of Alzheimer's and Parkinson's diseases. Both enantiomers have short plasma half-lives, and their pharmacokinetics might be improved through the use of either once or twice-daily administration of an extended-release dosage form. Phenserine was observed to form a colored degradation product in near-neutral and alkaline pH environments, and at pH 7, the half-life of posiphen was determined to be ~ 9 h (40 °C). To limit luminal degradation which would reduce bioavailability, a gastroretentive tablet composed of a polyethylene oxide-xanthan gum matrix was developed. When placed in simulated gastric fluid (pH 1.2), approximately 70% of the phenserine was released over a 12 h period, and no degradants were detected in the release medium. In comparison, a traditional hydrophilic-matrix, extended-release tablet showed measurable amounts of phenserine degradation in a pH 7.2 medium over an 8 h release interval. These results confirm that a gastroretentive tablet can reduce the luminal degradation of phenserine or posiphen by limiting exposure to neutral pH conditions while providing sustained release of the drug over at least 12 h. Additional advantages of the gastroretentive tablet include reduced gastric and intestinal concentrations of the drug resulting from the slower release from the gastroretentive tablet which may also limit the occurrence of the dose-limiting GI side effects previously observed with immediate-release phenserine capsules.

Physostigmine Reversal of Dysarthria and Delirium After Iatrogenic Atropine Overdose From a Dental Procedure.

BACKGROUND: Sublingual atropine, dosed at 0.4-0.8 mg, is used by dentists as an antisialogogue to facilitate and increase the speed of procedures. Concentrated ophthalmic atropine drops (10 mg/mL) are commonly used off-label for this purpose. These highly concentrated drops may result in medication errors, atropine toxicity, and the antimuscarinic toxidrome. We report a case of a man who suffered acute delirium and dysarthria (from dry mouth) after an iatrogenic overdose from a dental procedure. His symptoms were initially interpreted as a stroke, but they completely resolved with physostigmine. CASE REPORT: A 57-year-old man presented with acute dysarthria and delirium after a dental procedure; 4 hours earlier he was fitted for a temporary replacement of some premolar/molar teeth. He received sublingual atropine to assist in gingival drying for molding of his prosthesis, but a calculation error resulted in the administration of approximately 113 mg. A stroke evaluation was initially planned; however, 2.5 mg of intravenous physostigmine completely reversed his symptoms. His symptoms reoccurred and were successfully treated twice more with physostigmine; the patient was observed overnight with no additional symptoms and safely discharged the next morning. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Ophthalmic atropine drops are highly concentrated and may cause an overdose after ingestion of small amounts. This novel case highlights the importance of considering antimuscarinic poisoning in cases of acute delirium or dysarthria after dental procedures and stands as a reminder to inquire about the use of atropine drops in such cases. Timely recognition of the antimuscarinic toxidrome and appropriate use of physostigmine may prevent unnecessary testing while providing an effective therapy. This case also highlights the need for observation after resolution of delirium treated with physostigmine.

Revival of physostigmine - a novel HPLC assay for simultaneous determination of physostigmine and its metabolite eseroline designed for a pharmacokinetic study of septic patients.

BACKGROUND: Physostigmine, commonly used as an antidote in anticholinergic poisoning, is reported to have additional pharmacological effects, such as activation of the cholinergic anti-inflammatory pathway in sepsis models. Due to the narrow therapeutic range of physostigmine and its metabolite eseroline, however, the plasma concentrations of these substances need to be determined so as to understand their effect and ensure safety in the treatment of septic patients. METHODS: To determine physostigmine and its metabolite eseroline, a rapid and sensitive high performance liquid chromatography (HPLC) method has been developed and validated. Spiked plasma samples were cleaned up and concentrated using a simple liquid-liquid extraction (LLE) procedure with N-methylphysostigmine as internal standard. Separation was achieved using reversed-phase HPLC on a Kinetex C18 column with gradient elution and fluorescence detection (254 nm excitation/355 nm emission). RESULTS: LLE produced clean extracts and a mean recovery of 80.3% for eseroline and 84.9% for physostigmine. The HPLC assay revealed a limit of detection (LOD) of 0.025 ng/mL and a lower limit of quantification (LLOQ) of 0.05 ng/mL for both analytes. Linearity was observed at 0.05-10.0 ng/mL (r²>0.999). Intra- and inter-day precision ranged from 0.7% to 6.6%, and intra- and inter-day accuracy 97.5%-110.0%. CONCLUSIONS: The presented method is useful for human drug level monitoring of physostigmine and eseroline in accordance with current guidelines. Remarkably low plasma concentrations can be quantified after LLE with gradient elution and fluorescence detection, making this a suitable method for pharmacokinetic studies in a clinical setting.

Kinetics of Torpedo californica acetylcholinesterase inhibition by bisnorcymserine and crystal structure of the complex with its leaving group.

Natural and synthetic carbamates act as pseudo-irreversible inhibitors of AChE (acetylcholinesterase) as well as BChE (butyrylcholinesterase), two enzymes involved in neuronal function as well as in the development and progression of AD (Alzheimer's disease). The AChE mode of action is characterized by a rapid carbamoylation of the active-site Ser(200) with release of a leaving group followed by a slow regeneration of enzyme action due to subsequent decarbamoylation. The experimental AD therapeutic bisnorcymserine, a synthetic carbamate, shows an interesting activity and selectivity for BChE, and its clinical development is currently being pursued. We undertook detailed kinetic studies on the activity of the carbamate bisnorcymserine with Tc (Torpedo californica) AChE and, on the basis of the results, crystallized the complex between TcAChE and bisnorcymserine. The X-ray crystal structure showed only the leaving group, bisnoreseroline, trapped at the bottom of the aromatic enzyme gorge. Specifically, bisnoreseroline interacts in a non-covalent way with Ser(200) and His(440), disrupting the existing interactions within the catalytic triad, and it stacks with Trp(84) at the bottom of the gorge, giving rise to an unprecedented hydrogen-bonding contact. These interactions point to a dominant reversible inhibition mechanism attributable to the leaving group, bisnoreseroline, as revealed by kinetic analysis.

Posiphen as a candidate drug to lower CSF amyloid precursor protein, amyloid-ß peptide and τ levels: target engagement, tolerability and pharmacokinetics in humans.

AIM: A first in human study to evaluate tolerability and pharmacokinetics followed by an early proof of mechanism (POM) study to determine whether the small orally, available molecule, Posiphen tartrate (Posiphen), lowers secreted (s) amyloid-ß precursor protein (APP) α and -ß, amyloid-ß peptide (Aß), tau (τ) and inflammatory markers in CSF of patients with mild cognitive impairment (MCI). STUDY DESIGN: Posiphen single and multiple ascending dose phase 1 randomised, double blind, placebo-controlled safety, tolerance, pharmacokinetic studies were undertaken in a total of 120 healthy volunteers to define a dose that was then used in a small non-randomised study of five MCI subjects, used as their own controls, to define target engagement. MAIN OUTCOME MEASURES: Pharmacodynamic: sAPPα, sAPPß, Aß(42), τ (total (t) and phosphorylated (p)) and inflammatory marker levels were time-dependently measured over 12 h and compared prior to and following 10 days of oral Posiphen treatment in four MCI subjects who completed the study. Pharmacokinetic: plasma and CSF drug and primary metabolite concentrations with estimated brain levels extrapolated from steady-state drug administration in rats. RESULTS: Posiphen proved well tolerated and significantly lowered CSF levels of sAPPα, sAPPß, t-τ, p-τ and specific inflammatory markers, and demonstrated a trend to lower CSF Aß(42). CONCLUSIONS: These results confirm preclinical POM studies, demonstrate that pharmacologically relevant drug/metabolite levels reach brain and support the continued clinical optimisation and evaluation of Posiphen for MCI and Alzheimer's disease.

Dynamic physostigmine effects on hippocampus perfusion.

PURPOSE: To characterize the dynamic response of hippocampus blood flow to physostigmine infusion and to determine an infusion duration sufficiently long for robust detection of effects with arterial spin labeling (ASL) and sufficiently short to avoid peripheral side effects of physostigmine. MATERIALS AND METHODS: Two female (49 ± 15 years) and nine male (53 ± 13 years) subjects were studied to determine the time course of the physostigmine effect on hippocampus blood flow with ASL perfusion imaging during 20 minutes of baseline, 30 minutes of physostigmine infusion at 1.0 mg/hr, and 70 minutes of recovery. RESULTS: Hippocampus perfusion decreased steadily over the course of the infusion, with the reduction in flow becoming significant after 20 minutes of infusion, reaching lowest levels near the end of infusion, and remaining significantly low and stable in the 70-minute recovery period. Percentage changes of hippocampus perfusion were -13.3%, -13.4%, and -13.4% for left, right, and bilateral hippocampus, respectively, at the end of infusion. CONCLUSION: At a dose rate of 1.0 mg/hr it is feasible to use an infusion time as short as 20 minutes, performing perfusion imaging up to an hour after physostigmine infusion is discontinued, to minimize chances for adverse side effects.

Differential mRNA expression of acetylcholinesterase in the central nervous system of rats with acute and chronic exposure of sarin & physostigmine.

A time-course study was carried out to measure the acetylcholinesterase (AChE) gene expression in the brain of female rats exposed to different doses of sarin and physostigmine. Short-term effects were studied with an acute single subcutaneous dose (s.c.) of 80 microg kg(-1) (0.5 x LD(50)) sarin. Cortex and cerebellum showed a significant decline in AChE mRNA expression at 2.5, 24 and 72 h. Biochemical studies showed that plasma butrylcholinesterase (BChE) and brain AChE activities were significantly decreased at 2.5 h, which came back to near control values by 24 h in both cases. For long-term chronic studies, three groups of female rats received daily doses of physostigmine (0.1 mg kg(-1) day(-1)) intramuscularly (i.m.), sarin (15 microg kg(-1) day(-1)) s.c. independently and a combined dose of physostigmine (i.m.) (0.1 mg kg(-1) day(-1)) followed by sarin (s.c.) (15 microg kg(-1) day(-1)) continuously for 30 days. Differential AChE mRNA levels in cortex and cerebellum of rat brain were observed after 30 days and after a lag period of another 30 days with no further administration. Plasma (BChE) and brain (AChE) showed irregular inhibition profile in biochemical studies at 30 days and returned to control levels after 60 days. The acute single subcutaneous administration of sarin for short-term as well as chronic long-term studies showed that AChE inhibition alone does not lead to observed changes in mRNA expression of AChE gene. These observations further suggest that route of administration as well as dose exposure regimen also contributes to the regulation of AChE mRNA expression.

Evaluation of two scopolamine and physostigmine pretreatment regimens against nerve agent poisoning in the dog.

Currently, there is no viable protection against chemical warfare agents for the working dog. Physostigmine (PHY) and scopolamine (SCO) have been shown to protect dogs against nerve agents with minimal side effects. The goal of this study was to investigate whether reported protective SCO/PHY plasma concentrations of 0.2 and 0.7 ng/mL, respectively, could be reached and maintained with minimal side-effects thereby identifying possible pretreatment regimens. Two continuous regimens of SCO/PHY were administered to beagle dogs. The first regimen consisted of administering transdermal SCO and intraocular PHY, the second consisted of transdermal SCO and rectal PHY. SCO/PHY plasma concentrations for each regimen were determined, individual protective times were calculated and a computerized pharmacokinetic analysis was performed. The results showed transdermal SCO and intraocular PHY routes of delivery achieved sustained protective drug concentrations with minimal side-effects and the rectal route of delivery did not. Group median protective times for the first regimen were 54.45 h for SCO and 64.35 h for PHY, and for the second regimen 63.75 h for SCO and 0 h for PHY. The combined transdermal patch and intraocular regimen may provide a safe and effective regimen against nerve agent poisoning in dogs.

Continuous infusion of physostigmine in patients with perioperative septic shock: A pharmacokinetic/pharmacodynamic study with population pharmacokinetic modeling.

BACKGROUND: In the context of the cholinergic anti-inflammatory pathway, the clinical trial Anticholium® per Se (EudraCT Number: 2012-001650-26, ClinicalTrials.gov NCT03013322) addressed the possibility of taking adjunctive physostigmine salicylate treatment in septic shock from bench to bedside. Pharmacokinetics (PK) are likely altered in critically ill patients; data on physostigmine PK and target concentrations are sparse, particularly for continuous infusion. Our objective was to build a population PK (popPK) model for physostigmine, and further evaluate pharmacodynamics (PD) and concentration-response relationship in this setting. METHODS: In the randomized, double-blind, placebo-controlled trial, 20 patients with perioperative septic shock either received an initial dose of 0.04 mg/kg physostigmine salicylate, followed by continuous infusion of 1 mg/h for up to 120 h, or equivalent volumes of 0.9% sodium chloride (placebo group). Physostigmine plasma concentrations and acetylcholinesterase (AChE) activity were measured; concentration-response associations were evaluated, and popPK and PD modeling was performed with NONMEM. RESULTS: Steady state physostigmine plasma concentrations reached 7.60 ±â€¯2.81 ng/mL (mean ±â€¯standard deviation [SD]). PK was best described by a two-compartment model with linear clearance. Significant covariate effects were detected for body weight and age on clearance, as well as a high inter-individual variability of the central volume of distribution. AChE activity was significantly reduced to 30.5%-50.6% of baseline activity during physostigmine salicylate infusion. A sigmoidal direct effect PD model best described enzyme inhibition by physostigmine, with an estimated half maximal effective concentration (EC50) of 5.99 ng/mL. CONCLUSIONS: PK of physostigmine in patients with septic shock displayed substantial inter-individual variability with body weight and age influencing the clearance. Physostigmine inhibited AChE activity with a sigmoidal concentration-response effect.

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.

[Pharmacotherapy--physostigmine administered post-operatively]. / Pharmakotherapie--physostigmin post OP.

The central anticholinergic syndrome should be considered in patients with altered mental status following anaesthesia. Physostigmine, a reversible acetylcholinesterase inhibitor, is a first-line medicament for the therapy of the central anticholinergic syndrome. Physostigmine crosses the blood-brain barrier and elevates acetylcholine levels in the brain. For prevention of postanaesthetic shivering, for treatment of intoxications and postoperative pain, and for patients suspected of having antimuscarinic delirium physostigmine is also indicated.

Adjunctive use of physostigmine salicylate (Anticholium®) in perioperative sepsis and septic shock: study protocol for a randomized, double-blind, placebo-controlled, monocentric trial (Anticholium® per Se).

BACKGROUND: Severe sepsis and septic shock remain a major challenge, even in modern intensive care. In Germany, about 68,000 patients die annually because of septic diseases, characterized by a complex systemic inflammatory response. Causal treatment of the underlying infection is essential for successful management of sepsis, but the course can be positively influenced by supportive and adjuvant measures. The cholinergic anti-inflammatory pathway (CAP) represents a new approach to adjunctive therapy of septic diseases and can be pharmacologically activated by the acetylcholinesterase inhibitor physostigmine (Anticholium®). Promising effects can be found in several in vitro and in vivo models of sepsis, such as a reduction in pro-inflammatory cytokines and improved survival. METHODS: Anticholium® per Se is a randomized, double-blind, placebo-controlled, monocentric trial to assess whether the CAP can be transferred from bench to bedside. In this pilot study, 20 patients with perioperative sepsis and septic shock as a result of intra-abdominal infection are enrolled. According to randomization, participants are treated with physostigmine salicylate (verum group) or 0.9% sodium chloride (placebo group) for up to 5 days. The mean Sequential Organ Failure Assessment (SOFA) score during treatment and subsequent intensive care of up to 14 days is used as surrogate outcome (primary endpoint). Secondary outcome measures include 30- and 90-day mortality. An embedded pharmacokinetics and pharmacodynamics study investigates plasma concentrations of physostigmine and its metabolite eseroline. Further analyses will contribute to our understanding of the role of various cytokines in the pathophysiology of human sepsis. A computer-generated list is used for block randomization. DISCUSSION: This randomized, controlled, monocentric trial investigates for the first time the adjunctive use of physostigmine (Anticholium®) in patients with perioperative sepsis and septic shock and may be a pivotal step toward the clinical use in this indication. TRIAL REGISTRATION: EudraCT Number: 2012-001650-26 (entered 14 August 2012), ClinicalTrials.gov identifier: NCT03013322 (registered on 1 Jan 2017).

Kinetics of human serum butyrylcholinesterase and its inhibition by a novel experimental Alzheimer therapeutic, bisnorcymserine.

An explosion in the incidence of neurodegenerative diseases, particularly Alzheimer's disease (AD), is predicted in coming decades. Hence, the need to devise and assess new treatment strategies has never been more acute. AD, although an irreversible and progressive disorder, is currently treated with palliative, symptomatic therapy: primarily with acetylcholinesterase (AChE) inhibitors to amplify remaining cholinergic activity. New agents that, additionally, affect disease progression are sorely needed. Inhibition of brain butyrylcholinesterase (BuChE) represents a new drug target for AD treatment. Therefore, hand-in-hand with the development of selective ligands to inhibit BuChE in brain, it is fundamental to optimize assay conditions for kinetic studies of human BuChE. Kinetic analysis of serum BuChE, which is structurally similar to brain enzyme, was performed at dual substrate (butyrylthiocholine iodide) concentration ranges: 3-80 microM (low) and 25-800 microM (optimal) by use of the Ellman technique. Interaction of BuChE with a novel experimental AD therapeutic, bisnorcymserine (BNC; 0.06-2.0 nM) was also studied ex vivo. The IC_{50} and other key kinetic constants were determined for human serum BuChE inhibition by BNC, which proved to be a highly potent inhibitor in comparison to its structural analogue, cymserine. BNC may, additionally, lower the amyloid plaque-associated protein, amyloid-beta peptide. In synopsis, the characterization of the kinetic parameters of BuChE and BNC, described herein, is both aiding in the design of novel agents and optimizing their translation toward clinical use.

Pharmacokinetic and biodistribution study of eserine and pralidoxime chloride in rabbits following a single application of a transdermal patch.

In the present study, a simple reverse-phase high-performance liquid chromatography method with diode array detection has been developed and validated for the simultaneous determination and quantification of eserine and pralidoxime chloride in rabbit plasma and its application to pharmacokinetic study. The pharmacokinetic study was performed after transdermal application of single patch in rabbits. The plasma levels of both drugs following transdermal application of single patch were maintained for 72 h after removal of the patch. The maximal concentrations (C max) of both drugs were significantly reduced while the mean areas under the plasma concentration vs. time moment curve and mean residence times were evidently increased and extended, respectively. A sustained activity was observed over a period of 3 days. This sustained activity was due to the controlled release of drug into the systemic circulation following transdermal application. Linear correlation was also observed when fraction of drug permeated was correlated with the fraction of drug absorbed at the same time point. Gamma scintigraphy imaging on rabbit following transdermal patch application was performed to ascertain the localization of drugs in rabbit brain.

Physostigmine analogs anticholinesterases: effects of the lengthening of the N-carbamic chain on the inhibition kinetics.

Data are presented about the inhibitor power of new carbamates against acetylcholinesterase. The study was carried out on two series of physostigmine analogs, N-alkyl and N-methyl,N-alkylphysostigmines. For these inhibitors, the second-order rate constants for inhibition, ki, and the first-order rate constants of reactivation, k3, have been determined. From the reported results, electronic, hydrophobic and steric effects, due to the enhancement of the alkyl chain, may have influenced all kinetics parameters discussed. In comparison to physostigmine, both the new N-methyl,N-alkylphysostigmines and the N-alkylphysostigmines showed a non-linear decrease in the values of ki and k3. This study presents the hydrophobic interactions as an important factor not only in determining carbamylation but also decarbamylation rates constants.

Anticholinesterasic drugs: tacrine but not physostigmine, accumulates in acidic compartments of the cells.

Tacrine (THA) and physostigmine (PHS) have been used in Alzheimer's disease therapy for their anticholinesterasic activity. Here we show that THA is taken up in rat lysosomes in an energy-dependent manner, and that it is also accumulated in acidic compartments of rat thymocytes and neuroblastoma cells. A concentration of THA less than 1 mM dissipated the pH gradient (delta pH) in all the above mentioned in vitro systems. On the contrary higher concentrations of PHS (1-2 mM) were ineffective. The accumulation of THA in acidic organelles of the cell may be relevant for the pharmacological action of THA in Alzheimer's treatment.

Cholinergic effects on fear conditioning I: the degraded contingency effect is disrupted by atropine but reinstated by physostigmine.

RATIONALE: The cholinergic system has been shown to modulate contextual fear conditioning. However, with the exception of trace conditioning studies, most of the available data have focussed on independent context, i.e., context that do not compete with the conditioned stimulus to control for the conditioned response (interactive context). OBJECTIVE: In the present series of experiments, the effects of the muscarinic antagonist, atropine, were assessed when contextual fear memory interacts with cued fear memory to regulate conditioned response, using a Pavlovian degraded contingency preparation in rats. This preparation not only afforded an insight into simple Pavlovian associations but also enabled us to test for the processes of competition that made use of these associations to make an appropriate response to a stimulus [degraded contingency effect (DCE)]. METHODS: In experiment 1, three doses of atropine [2.5, 5.0, and 10.0 mg/kg, intraperitoneally (i.p.)] were evaluated on male Sprague-Dawley rats. In experiment 2, physostigmine (0.037-0.3 mg/kg, i.p.) was injected after the administration of 5 mg/kg of atropine. RESULTS: Experiment 1A and its partial replication (experiment 1B) showed that at asymptotic level of training, atropine did not alter contextual and cued fear memories when the subjects were directly tested for them, whereas it suppressed the DCE for a 5 mg/kg dose. Indeed, atropine-induced suppression of the DCE was found to be an inverted U-shaped dose-response curve. Experiment 2 showed that physostigmine caused a dose-dependent reversal of the atropine-induced alleviation of the DCE, without altering the expression of simple cued and contextual fear memories. CONCLUSION: These results evidence at asymptotic level of training a cholinergic modulation of the processing of interactive context, but not of independent ones. They are discussed in the framework of the mechanisms that are involved in both types of contextual processing.

An overview of phenserine tartrate, a novel acetylcholinesterase inhibitor for the treatment of Alzheimer's disease.

Existing cholinesterase (ChE) inhibitor therapies for Alzheimer's disease (AD), while effective in improving cognitive, behavioral and functional impairments, do not alter disease progression. Novel drug design studies have focused on the classical ChE inhibitor, (-)-physostigmine, producing alterations in chemical composition and three-dimensional structure, which may offer an improved therapeutic index. The phenylcarbamate derivative, (-)-phenserine, is a selective, non-competitive inhibitor of acetylcholinesterase (AChE). In vivo, (-)-phenserine produces rapid, potent, and long-lasting AChE inhibition. As a possible result of its preferential brain selectivity, (-)-phenserine is significantly less toxic than (-)-physostigmine. In studies using the Stone maze paradigm, (-)-phenserine has been shown to improve cognitive performance in both young learning-impaired and elderly rats. In addition to reducing inactivation of acetylcholine in the brain, (-)-phenserine appears to have a second mode of action. Reduced secretion of beta-amyloid (Abeta) has been observed in cell lines exposed to (-)-phenserine, occurring through translational regulation of beta-amyloid precursor protein (beta-APP) mRNA via a non-cholinergic mechanism. These in vitro findings appear to translate in vivo into animal models and humans. In a small study of patients with AD, (-)-phenserine treatment tended to reduce beta-APP and Abeta levels in plasma samples. Clinical studies also reveal that (-)-phenserine (5-10 mg b.i.d.) had a favorable safety and pharmacological profile, produced significant improvements in cognitive function and was well tolerated in patients with AD treated for 12 weeks. Further randomized, double-blind, placebo-controlled Phase III studies assessing the efficacy, safety/tolerability and potential disease-modifying effects of (-)-phenserine in patients with AD are currently ongoing.

Anticholinesterase and pharmacokinetic profile of phenserine in healthy elderly human subjects.

OBJECTIVE: To evaluate the safety, maximum tolerated dose (MTD), pharmacokinetics (PK), and pharmacodynamics (PD) of the acetyl-selective anticholinesterase, phenserine tartrate, in healthy elderly subjects. METHODS: 32 healthy elderly volunteers received single oral doses of phenserine tartrate (5-20 mg). Physical and vital signs were monitored over the ensuing 24 hours. Analyses were performed on plasma samples to determine PK, and PD were assessed using an erythrocyte acetylcholinesterase (AChE) inhibition assay. RESULTS: No serious adverse events (AEs) occurred; the most common were headache and vomiting. The MTD of phenserine tartrate was 10 mg. The Cmax and AUC(0-24) of phenserine increased with dose, but neither were dose-proportional. Subjects receiving 10 mg of phenserine tartrate had a Cmax of 1.95 ng/mL at 1.5 hours, and the mean peak inhibition (Imax) of AChE was 26% (range: 18-34%) at 1.75 hours (tImax) following dosing. The half-life of AChE inhibition (tI1/2) was 11 hours. Evaluation of PK/PD relationships suggested a linear correlation between plasma phenserine concentration and AChE inhibition in the blood. CONCLUSIONS: Phenserine tartrate was safe and well tolerated when administered as a single oral dose of either 5 mg or 10 mg. An increase in the severity and frequency of AEs occurred at the 20 mg dose level.

Skin permeation of physostigmine from fatty acids-based formulations: evaluating the choice of solvent.

This study was conducted to gain an understanding of the enhancement mechanism of fatty acids in skin permeation of physostigmine (PHY) by using a series of fatty acids and two solvents of opposing lipophilicity (propylene glycol (PG) and mineral oil (MO)). Interaction between fatty acid and drug was proven using NMR and conductivity measurements that showed a dependence on type of solvent used. Permeation flux of physostigmine from mineral oil-based formulations to skin was increased as solubility of physostigmine in mineral oil was enhanced in the presence of fatty acids having a longer chain. Thus, the dominant role of fatty acids in mineral oil was to increase solubility of physostigmine in the formulations that increased the driving force for physostigmine permeation through skin. As for propylene glycol, enhancement caused by fatty acids was attributed to their ability to increase the lipophilicity of formulation and to disrupt the lipid bilayers within the stratum corneum (SC). In conclusion, fatty acids enhancement for drug permeation across the skin was found to be dependent on the solvent used. Among various formulations here, oleic acid in mineral oil yielded fast permeation of PHY with a short lag time, which may be a good vehicle for transdermal delivery of PHY.