Topical ophthalmic atropine in horses, pharmacokinetics and effect on intestinal motility.

BACKGROUND: Topical ophthalmic atropine sulfate is an important part of the treatment protocol in equine uveitis. Frequent administration of topical atropine may cause decreased intestinal motility and colic in horses due to systemic exposure. Atropine pharmacokinetics are unknown in horses and this knowledge gap could impede the use of atropine because of the presumed risk of unwanted effects. Additional information could therefore increase safety in atropine treatment. RESULTS: Atropine sulfate (1 mg) was administered in two experiments: In part I, atropine sulfate was administered intravenously and topically (manually as eye drops and through a subpalpebral lavage system) to six horses to document atropine disposition. Blood-samples were collected regularly and plasma was analyzed for atropine using UHPLC-MS/MS. Atropine plasma concentration was below lower limit of quantification (0.05 µg/L) within five hours, after both topical and IV administration. Atropine data were analyzed by means of population compartmental modeling and pharmacokinetic parameters estimated. The typical value was 1.7 L/kg for the steady-state volume of distribution. Total plasma clearance was 1.9 L/h‧kg. The bioavailability after administration of an ophthalmic preparation as an eye drop or topical infusion were 69 and 68%, respectively. The terminal half-life was short (0.8 h). In part II, topical ophthalmic atropine sulfate and control treatment was administered to four horses in two dosing regimens to assess the effect on gastro-intestinal motility. Borborygmi-frequency monitored by auscultation was used for estimation of gut motility. A statistically significant decrease in intestinal motility was observed after administration of 1 mg topical ophthalmic atropine sulfate every three hours compared to control, but not after administration every six hours. Clinical signs of colic were not observed under any of the treatment protocols. CONCLUSIONS: Taking the plasma exposure after topical administration into consideration, data and simulations indicate that eye drops administrated at a one and three hour interval will lead to atropine accumulation in plasma over 24 h but that a six hour interval allows total washout of atropine between two topical administrations. If constant corneal and conjunctival atropine exposure is required, a topical constant rate infusion at 5 µg/kg/24 h offers a safe alternative.

Pharmacokinetics and efficacy of atropine sulfate/obidoxime chloride co-formulation against VX in a guinea pig model.

Nerve agent exposure is generally treated by an antidote formulation composed of a muscarinic antagonist, atropine sulfate (ATR), and a reactivator of acetylcholinesterase (AChE) such as pralidoxime, obidoxime (OBI), methoxime, trimedoxime or HI-6 and an anticonvulsant. Organophosphates (OPs) irreversibly inhibit AChE, the enzyme responsible for termination of acetylcholine signal transduction. Inhibition of AChE leads to overstimulation of the central and peripheral nervous system with convulsive seizures, respiratory distress and death as result. The present study evaluated the efficacy and pharmacokinetics (PK) of ATR/OBI following exposure to two different VX dose levels. The PK of ATR and OBI administered either as a single drug, combined treatment but separately injected, or administered as the ATR/OBI co-formulation, was determined in plasma of naïve guinea pigs and found to be similar for all formulations. Following subcutaneous VX exposure, ATR/OBI-treated animals showed significant improvement in survival rate and progression of clinical signs compared to untreated animals. Moreover, AChE activity after VX exposure in both blood and brain tissue was significantly higher in ATR/OBI-treated animals compared to vehicle-treated control. In conclusion, ATR/OBI has been proven to be efficacious against exposure to VX and there were no PK interactions between ATR and OBI when administered as a co-formulation.

Comparative physiology and efficacy of atropine and scopolamine in sarin nerve agent poisoning.

Anticholinergic treatment is key for effective medical treatment of nerve agent exposure. Atropine is included at a 2 mg intramuscular dose in so-called autoinjectors designed for self- and buddy-aid. As patient cohorts are not available, predicting and evaluating the efficacy of medical countermeasures relies on animal models. The use of atropine as a muscarinic antagonist is based on efficacy achieved in studies in a variety of species. The dose of atropine administered varies considerably across these studies. This is a complicating factor in the prediction of efficacy in the human situation, largely because atropine dosing also influences therapeutic efficacy of oximes and anticonvulsants generally part of the treatment administered. To improve translation of efficacy of dosing regimens, including pharmacokinetics and physiology provide a promising approach. In the current study, pharmacokinetics and physiological parameters obtained using EEG and ECG were assessed in naïve rats and in sarin-exposed rats for two anticholinergic drugs, atropine and scopolamine. The aim was to find a predictive parameter for therapeutic efficacy. Scopolamine and atropine showed a similar bioavailability, but brain levels reached were much higher for scopolamine. Scopolamine exhibited a dose-dependent loss of beta power in naïve animals, whereas atropine did not show any such central effect. This effect was correlated with an enhanced anticonvulsant effect of scopolamine compared to atropine. These findings show that an approach including pharmacokinetics and physiology could contribute to improved dose scaling across species and assessing the therapeutic potential of similar anticholinergic and anticonvulsant drugs against nerve agent poisoning.

Application of surface molecular imprinted magnetic graphene oxide and high performance mimetic behavior of bi-metal ZnCo MOF for determination of atropine in human serum.

Herein, high performance peroxidase-like activity of zinc and cobalt bi-metal metal-organic framework (ZnCo MOF) is reported and applied for the sensitive measurement of atropine. ZnCo MOF was synthesized by the reaction of 2-methylimidazole with Zn and Co (II) cations in aqueous media. The colorimetric and fluorometric experiments were applied to investigate the catalytic activity of obtained MOF, using o-phenylenediamine (OPD) and terephthalic acid (TA) peroxidase substrates, respectively. The results demonstrated the more efficient mimetic behavior of ZnCo MOF compared with common Zn or Co MOFs. Besides, it was found that atropine hindered the catalytic action of ZnCo MOF and this effect was intensified by increasing the atropine concentration. So, it was considered to design a sensitive analytical assay for atropine detection. To assure a high specific recognition, molecularly imprinted polymer (MIP)-based extraction using magnetic graphene oxide supports was applied to extract atropine before its determination. The combination between the high specific extraction and great catalytic activity of ZnCo MOF led to the ultrasensitive and reliable determination of atropine. The best linear range of calibration graph was achieved using fluorometric detection system for 0.1-45 ng mL-1 atropine concentrations, and detection limit (3Sb/m) was 27 pg mL-1. The relative standard deviations (RSD %) for the determination of 1, and 10 ng mL-1 atropine (n = 5) were 2.13% and 3.08%, respectively. The explained fluorometric assay was examined for the measurement of atropine in biological fluids (Recoveries were in the range of 95.90-103.57%), and the results were validated by an official method.

Specific quantification of atropine using molecularly imprinted polymer on graphene quantum dots.

Herein, development of a reliable and specific fluorometric assay was disclosed for the sensitive detection of atropine. The method was designed using the surface molecularly imprinted polymer on high fluorescent graphene quantum dots (GQDs). Molecularly imprinted polymer capped GQDs (MIP-GQDs) were prepared through the common co-polymerization reaction of 3-(3-aminopropyl) triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS), act as the main functional and cross-linking monomers, respectively. The used template for this reaction was atropine. The created blue luminescent MIP-GQDs composite, which had a great affinity to adsorb atropine from the sample solution, could lead to a notable fluorescence quenching. In fact, GQDs act as the recognizing antenna for adsorbed atropine into the specific MIP sites. The linear association between the observed quenching effect and atropine concentration was exploited to design a selective assay to the detection of atropine. After optimization process, a linear calibration graph was achieved in the atropine concentration range of 0.5-300 ng mL-1 with a detection limit of 0.22 ng mL-1. Exploitation of high specific MIP technique along with high fluorescent GQDs provided a highly selective and sensitive assay for atropine as a model analyte. It was adequately utilized for the analysis of atropine in biological samples.

Objective evaluation of the systemic effects of topical application of 1% atropine sulfate ophthalmic solution in healthy horses.

OBJECTIVE To determine the safety of topical administration of 1% atropine ophthalmic solution in healthy horses by objectively measuring gastrointestinal transit time. DESIGN Randomized, masked, controlled crossover study. ANIMALS 6 adult geldings. PROCEDURES Horses were randomly assigned (3/group) to first receive topical treatment of the left eye with 1% atropine or artificial tears solution; the right eye was left untreated. After 24 hours of treatment every 6 hours, 200 nontoxic beads were administered to each horse via nasogastric intubation and treatment frequency was decreased to every 12 hours for 4 more days. Pupillary light reflexes (PLRs), mydriasis, heart rate, fecal bead passage, abdominal girth measurements, auscultable gut sounds, fecal weight, and clinical signs of abdominal pain were monitored. Following a 4-week washout period, horses received the opposite treatment in the left eye and measurements were repeated. Serum atropine concentration (reflecting systemic absorption) was measured with an ELISA at various points after initial atropine administration. RESULTS No horse had subjective or objective evidence of colic or ileus at any monitoring point. Complete mydriasis of the left eye with absence of the PLR was identified in 5 horses within 6 hours and in all 6 horses within 12 hours after initial atropine administration. One horse had mydriasis with an absent PLR in the untreated eye by day 5 of atropine treatment. At no point was atropine detected in serum samples of any horse. CONCLUSIONS AND CLINICAL RELEVANCE Topical atropine application at clinically appropriate doses induced no evidence of ileus in healthy horses.

The pharmacokinetics of intraosseous atropine in hypovolemic swine.

OBJECTIVE: Compare the pharmacokinetics of atropine administered via the intravenous (IV), intramuscular (IM), and intraosseous (IO) routes in a normovolemic and hypovolemic swine model. DESIGN: Prospective, between subjects, experimental study. SETTING: Vivarium. SUBJECTS: Yorkshire-cross swine (N = 36). INTERVENTION: Atropine was administered via IV, IM, or IO routes to normovolemic and hypovolemic swine. Blood samples were drawn at regular intervals after atropine administration and analyzed for plasma atropine concentration. Pharmacokinetic parameters were obtained from modeling the plasma concentrations. MAIN OUTCOME MEASUREMENTS: Pharmacokinetic parameters, maximum concentration (Cmax) and time to maximum concentration (Tmax). RESULTS: The IV and IO groups in both the normovolemic and hypovolemic models reached peak plasma concentration immediately and had a very rapid distribution phase with no apparent absorption phase for the IO groups. Peak plasma concentration and time to reach peak concentration were both significantly lower for the IM groups. There was a significant increase in absorption time with IM administration in the hypovolemic model compared to the normovolemic model. CONCLUSION: The IO route is an effective method of administering atropine and is comparable to the IV route even under conditions of significant hemorrhage. Therapeutic levels of atropine may be delayed and possibly difficult to obtain via IM injection in the presence of hypovolemic shock.

Determination of atropine sulfate using a novel sensitive DNA-biosensor based on its interaction on a modified pencil graphite electrode.

A novel, selective, rapid and simple electrochemical method is developed for the determination of atropine sulfate. UV-Vis and differential pulse voltammetry are used to study the interaction of atropine sulfate with salmon sperm ds-DNA on the surface of salmon sperm ds-DNA modified-pencil graphite electrode (PGE). For this purpose, a pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs), titanium dioxide nanoparticles (TiO2NPs), and poly-dialyldimethylammonium chloride (PDDA) decorated with ds-DNA is tested for the determination of atropine sulfate. The electrochemical oxidation peak current of adenine and guanine bonded on the surface of ds-DNA/PDDA-TiO2NPs-MWCNTs/PGE is used to obtain the analytical signal. Decreases in the intensities of guanine and adenine oxidation signals after their interaction with atropine sulfate are used as indicator signals for the sensitive determination of atropine sulfate. Using ds-DNA/PDDA-TiO2NPs-MWCNTs/PGE and based on the guanine signal, linear calibration curves were obtained in the range of 0.6 to 30.0 µmol L(-1) and 30.0 to 600.0 µmol L(-1) atropine sulfate with low detection limits of 30.0 nmol L(-1). The biosensor shows a good selectivity for the determination of atropine sulfate. Finally, the applicability of the biosensor is evaluated by measuring atropine sulfate in real samples with good accuracy.

Simultaneous determination of atropine, scopolamine, and anisodamine from Hyoscyamus niger L. in rat plasma by high-performance liquid chromatography with tandem mass spectrometry and its application to a pharmacokinetics study.

In order to investigate the pharmacokinetics of tropane alkaloids in Hyoscyamus niger L., a sensitive and specific high-performance liquid chromatography with tandem mass spectrometry method for the simultaneous determination of atropine, scopolamine, and anisodamine in rat plasma is developed and fully validated, using homatropine as an internal standard. The separation of the four compounds was carried out on a BDS Hypersil C18 column using a mobile phase consisting of acetonitrile and water (containing 10 mmol ammonium acetate). Calibration curves were linear from 0.2 to 40 ng/mL for atropine, scopolamine, and from 0.08 to 20 ng/mL for anisodamine. The precision of three analytes was <5.89% and the accuracy was between -1.04 to 2.94%. This method is successfully applied to rat pharmacokinetics analysis of the three tropane alkaloids after oral administration of H. niger extract. The maximum concentration of these three tropane alkaloids was reached within 15 min, and the maximum concentrations were 31.36 ± 7.35 ng/mL for atropine, 49.94 ± 2.67 ng/mL for scopolamine, and 2.83 ± 1.49 ng/mL for anisodamine. The pharmacokinetic parameters revealed areas under the curve of 22.76 ± 5.80, 16.80 ± 3.08, and 4.31 ± 1.21 ng/h mL and mean residence times of 2.08 ± 0.55, 1.19 ± 0.45, and 3.28 ± 0.78 h for atropine, scopolamine, and anisodamine, respectively.

Simple validated LC-MS/MS method for the determination of atropine and scopolamine in plasma for clinical and forensic toxicological purposes.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of atropine and scopolamine in 100µL human plasma was developed and validated. Sample pretreatment consisted of protein precipitation with acetonitrile followed by a concentration step. Analytes and levobupivacaine (internal standard) were separated on a Zorbax XDB-CN column (75mm×4.6mm i.d., 3.5µm) with gradient elution (purified water, acetonitrile, formic acid). The triple quadrupole MS was operated in ESI positive mode. Matrix effect was estimated for deproteinised plasma samples. Selected reaction monitoring (SRM) was used for quantification in the range of 0.10-50.00ng/mL. Interday precision for both tropanes and intraday precision for atropine was <10%, intraday precision for scopolamine was <14% and <18% at lower limit of quantification (LLOQ). Mean interday and intraday accuracies for atropine were within ±7% and for scopolamine within ±11%. The method can be used for determination of therapeutic and toxic levels of both compounds and has been successfully applied to a study of pharmacodynamic and pharmacokinetic properties of tropanes, where plasma samples of volunteers were collected at fixed time intervals after ingestion of a buckwheat meal, spiked with five low doses of tropanes.

Rapid and complete bioavailability of antidotes for organophosphorus nerve agent and cyanide poisoning in minipigs after intraosseous administration.

STUDY OBJECTIVE: Management of chemical weapon casualties includes the timely administration of antidotes without contamination of rescuers. Personal protective equipment makes intravenous access difficult but does not prevent intraosseous drug administration. We therefore measured the systemic bioavailability of antidotes for organophosphorus nerve agent and cyanide poisoning when administered by the intraosseous, intravenous, and intramuscular routes in a small study of Göttingen minipigs. METHODS: Animals were randomly allocated to sequentially receive atropine (0.12 mg/kg by rapid injection), pralidoxime (25 mg/kg by injection during 2 minutes), and hydroxocobalamin (75 mg/kg during 10 minutes) by the intravenous or intraosseous route, or atropine and pralidoxime by the intramuscular route. Plasma concentrations were measured for 6 hours to characterize the antidote concentration-time profiles for each route. RESULTS: Maximum plasma concentrations of atropine and pralidoxime occurred within 2 minutes when administered by the intraosseous route compared with 8 minutes by the intramuscular route. Maximum plasma hydroxocobalamin concentration occurred at the end of the infusion when administered by the intraosseous route. The mean area under the concentration-time curve by the intraosseous route was similar to the intravenous route for all 3 drugs and similar to the intramuscular route for atropine and pralidoxime. CONCLUSION: This study showed rapid and substantial antidote bioavailability after intraosseous administration that appeared similar to that of the intravenous route. The intraosseous route of antidote administration should be considered when intravenous access is difficult.

Relative bioavailability and pharmacodynamic effects of methantheline compared with atropine in healthy subjects.

OBJECTIVES: Methantheline is a strong muscarinic receptor blocking drug used in the treatment of overactive bladder syndrome, hypersalivation and hyperhidrosis. To provide basic information on the pharmacokinetics, magnitude of pharmacodynamic (PD) effects and their correlations with plasma concentrations, we performed a clinical study in 12 healthy subjects receiving methantheline as immediate-release coated tablets (IR) or in watery solution (SOL) in comparison with atropine and placebo tablets. METHODS: The pharmacokinetics and influence of methantheline, atropine and placebo on salivation and accommodation and pupil function (pupillometry: diameter, response to light flash) were studied in a randomized, controlled study after the administration of 100 mg methantheline bromide as IR and in SOL (phase 1) and 1.0 mg atropine sulphate and placebo (phase 2). RESULTS: Methantheline reached maximum plasma concentrations of approximately 25 ng/ml after 2.5-3 h and was eliminated at an apparent half-life of approximately 2 h. There was no pharmacokinetic (PK) bioequivalence of methantheline IR and SOL. The ratio IR/SOL (90 % confidence interval) were 0.892 (0.532-1.493) for AUC(0-∞) and 0.905 (0.516-1.584) for maximum plasma concentration. The PD effects of both forms were nearly equivalent with a IR/SOL ratio of 1.015 (0.815-1.262) for salivation, which is the most susceptible characteristic. Methantheline reduced salivation at a potency (methantheline concentration at half maximum effects, EC50) of 5.5 ng/ml in accordance with it plasma concentration. The antimuscarinic effects observed after methantheline administration were stronger and persisted longer than those following the administration of atropine. CONCLUSIONS: Methantheline is slowly absorbed but rapidly eliminated in humans, and it exerts a strong effect on salivation which is closely associated with its plasma concentrations following a standard sigmoid PD model. Immediate-release tablets and a watery solution of methantheline are equivalent in terms of major PD effects (salivation, pupil function, heart rate) despite its high PK variability.

Application of an enantioselective LC-ESI MS/MS procedure to determine R- and S-hyoscyamine following intravenous atropine administration in swine.

S-hyoscyamine (S-hyo) is a natural plant tropane alkaloid acting as a muscarinic receptor (MR) antagonist. Its racemic mixture (atropine) is clinically used in pre-anaesthesia, ophthalmology and for the antidotal treatment of organophosphorus (OP) poisoning with nerve agents or pesticides even though R-hyo exhibits no effects on MR. Further investigative research is required to optimize treatment of OP poisoning. Swine are often the animal model utilized due to similarities in physiology and antidote response to humans. However, no studies have been reported that elucidated differences in the kinetics of R- and S-hyo. Therefore, the concentration-time profiles of total hyo as well as both enantiomers were analyzed in plasma after intravenous administration of atropine sulfate (Atr(2) SO(4) , 100 µg/kg) to anaesthetized swine. For quantification plasma samples were incubated separately with human serum (procedure A) and rabbit serum (procedure B). The rabbit serum used contained atropinesterase, which is suitable for stereoselective hydrolysis of S-hyo, while human serum does not hydrolyze either enantiomer. After incubation samples were precipitated and the supernatant was analyzed by RP-HPLC-ESI MS/MS. Procedure A allowed determination of total hyo and procedure B remaining R-hyo concentrations. S-hyo was calculated as the difference of the two procedures. Concentration data were regressed by a two-phase decay according to a two-compartment open model revealing similar kinetics for both enantiomers thus indicating distribution, metabolism and elimination without obvious stereoselective preference in tested swine.

A simple and sensitive GC/MS method for the determination of atropine during therapy of anticholinesterase poisoning in serum samples.

Atropine is used in the daily clinical practice for the treatment of poisonings caused by anticholinesterase pesticides, due to its sympathomimetic action. The investigation of the cause of the adverse effects that appear during atropine administration showed the necessity for the development and validation of a simple, rapid, sensitive, and specific method for the determination of atropine levels in serum samples. The developed method includes liquid-liquid extraction with ethyl acetate: dichloromethane (3:1, v/v) and derivatization using N,O-bis(trimethylsilyl)-trifluoracetamide (BSTFA) with 1% trimethylchlorsilane (TMCS) in acetonitrile environment. The method was found to be selective, linear, accurate, and precise according to international guidelines. The recovery was higher than 85.9%, the limit of quantification was 2.00 ng/ml, and the calibration curve was linear within the range of 2.00-500 ng/ml (R(2) ≥ 0.992). Accuracy and precision were also calculated and were found to be less than 5.2 and 8.7%, respectively. The developed method was applied in a real case of accidental poisoning with chlorpyrifos in order to determine the atropine serum levels of the patient. The proposed method proved to be useful for the investigation of adverse effects that appear during atropine treatment of patients poisoned by anticholinesterase pesticides and it can also be used for the investigation of poisonings caused after consumption of atropine containing plants.

Postmortem atropine concentrations in resuscitation cases.

The medications used during resuscitation are often in and of themselves toxic. Several reports have been published regarding toxicities of these drugs, including lidocaine, procainamide, and atropine. But how does a forensic pathologist or toxicologist differentiate a possible intoxication from therapeutic or resuscitory use especially given that the concentrations of such drugs, when used in the setting of resuscitation, have not been studied? Concentrations of a well-known resuscitation medication, atropine, were assessed in cases where it was administered before death during attempted resuscitation in an effort to address this deficiency. A review of deaths occurring in 2009 was undertaken to identify cases where drugs known to be used during resuscitation were present on toxicological analysis. Autopsy reports and medical records were examined to determine how much atropine was administered, the timing and route of administration, the time the sample was drawn (antemortem and postmortem), the source of the sample, and the ultimate cause of death. Eighty-nine cases were identified in which atropine was given before death during attempted resuscitation and was detected in the blood on postmortem toxicological screening; 11 cases were identified in which atropine was administered before death yet was not detected on the postmortem toxicological screening. Mean age was 41 years, and there were 65 males and 35 females. The overall median dose of atropine given was 3 mg, the median difference between the time of last administration of the atropine to the time of death (or draw for antemortem samples) was 15 minutes, and the median atropine concentration was 0.1 mg/L. Analysis failed to reveal significant differences in the atropine concentration based on the route of administration (intravenous or intraosseus), the cause of death, or the time since administration (within the first 2 hours). Analysis did reveal a difference between the atropine concentrations in peripheral versus central blood sources and with prolonged postmortem interval (>24 hours) suggesting postmortem redistribution.

[State under the influence of drugs or psychotropic agents--a comparison of toxicological and medical examinations in materials of the Department of Forensic Medicine and Toxicology, Silesian University of Medicine, Katowice]. / Stan "pod wplywem substancji odurzajacych lub psychotropowych" porównanie wyników badan toksykologicznych z ocena lekarska w materialach Katedry i Zakladu Medycyny Sadowej i Toksykologii Sadowo-Lekarskiej Slaskiego Uniwersytetu Medycznego w Katowicach.

In the paper, the authors present the results of toxicological examinations of blood samples taken from drivers during road check procedures or from perpetrators of traffic road accidents, which--taking into consideration the kind of the determined agents and their concentrations--were compared with the results of medical examinations from blood sampling protocols studied in the Department of Forensic Medicine and Toxicology, Silesian University of Medicine. All the blood samples were first analyzed using an immunoenzymatic assay (ELISA). Then, the LC-MS method was used. The positive results of screening for the presence of cannabinols were verified by GC-MS. Out of 329 blood samples, 145 were positive. The presence of cannabinols, amphetamine or MDMA was the most predominant finding. Diazepam was determined in 4 cases and opiates in 1 case. Only in 31% cases did positive results of toxicological examinations correspond to deviations found during the medical examinations constituting the basis for the final diagnosis of state "under the influence". In practice, appraisal of drug influence during medical examination seems to be limited and dependent on variable reactions of the examined individuals to a psychoactive agent, time lapse between the traffic road event and the examination or concomitant symptoms associated with ethylene alcohol activity. The final diagnosis of state "under the influence of drugs" or "under the influence of psychotropic agents" given by the physician does not result from the effect of these substances observed during the medical examination, but is very often formulated based on the medical history or police findings. The analysis of the above mentioned cases where Delta9THC or/and amphetamine was detected showed no correlation between the concentration of the psychoactive agent determined in blood and symptoms triggered by its action as described by the physician.

Atropine maintenance dosage in patients with severe organophosphate pesticide poisoning.

Although the importance of atropine in therapy of organophosphate (OP) poisoning is generally recognized, its dosing is a matter of debate. A retrospective analysis of atropine dosing was undertaken in 34 patients who had been enrolled in a clinical study assessing obidoxime effectiveness in OP-poisoning. All patients were severely intoxicated (suicidal attempts) and required artificial ventilation. Atropine was administered routinely by intensive care physicians for life-threatening muscarinic symptoms, with the recommendation to favor low dosage. The pharmacological active enantiomere S-hyoscyamine was determined by a radioreceptor assay. When RBC-AChE activity ranged between 10% and 30%, S-hyoscyamine plasma concentrations of approx. 5 nmol L⁻¹ were sufficient. This concentration could be maintained with about 0.005 mg h⁻¹ kg⁻¹ atropine. Only when RBC-AChE was completely inhibited, therapy of cholinergic crisis required atropine doses up to 0.06 mg h⁻¹ kg⁻¹. Elimination half-life of S-hyoscyamine was 1.5 h, showing occasionally a second slow elimination phase with t(½)=12 h. Malignant arrhythmias were observed in some 10% of our cases, which occurred late and often in the absence of relevant glandular cholinergic signs, when the S-hyoscyamine concentration was below 2.5 nmol L⁻¹. Arrhythmias mostly resolved on reinstitution of atropine.

High-performance liquid-chromatographic tandem-mass spectrometric methods for atropinesterase-mediated enantioselective and chiral determination of R- and S-hyoscyamine in plasma.

S-hyoscyamine (S-hyo) is a toxic tropane alkaloid from plants of the solanacea family, which is extracted for pharmaceutical purposes thereby undergoing racemization (atropine). Merely the S-hyo enantiomer acts as an antagonist of muscarinic receptors (MR). Nevertheless, racemic atropine is clinically administered in e.g. ophthalmology and for symptomatic therapy of acute poisoning with organophosphorus compounds (OPCs, e.g. pesticides, nerve agents). However, very limited data are available of comparative pharmacokinetics of S- and R-enantiomers in humans or other species. Therefore, we developed an enantioselective LC-ESI-MS/MS assay making use of rabbit serum containing atropinesterase (AtrE, EC 3.1.1.10) which is suitable for stereospecific hydrolysis of S-hyo into tropine and tropic acid while R-hyo is unaffected. For sample preparation plasma was incubated with human serum (not containing AtrE, procedure A) and with rabbit serum (procedure B). Afterwards, hyoscyamines were quantified by a validated previously published non-chiral LC-ESI-MS/MS method. Following procedure A the concentration of total hyo and following procedure B remaining R-hyo were determined. S-hyo was calculated by the difference between these concentrations. This assay design allowed reproducible, precise (RSD 2-9%), accurate (93-101%) and selective determination of total and individual hyoscyamines. Potential therapeutics for OPC poisoning (carbamates, oximes) and thiono-pesticides did not interfere with the assay whereas some oxon-pesticides inhibited S-hyo hydrolysis. A control experiment was designed allowing to be aware of such interferences thus avoiding the use of false results. To validate this assay, results were compared to those from a novel isocratic chiral LC-ESI-MS/MS method. Separation of S-hyo (t(R) 31.1 ± 0.2 min) and R-hyo (t(R) 33.4 ± 0.2 min) was achieved on α-glycoprotein (AGP) chiral stationary phase at 40°C (selectivity factor α 1.07). Ammoniumformate (0.01 M, pH 8.0) with 3.75% (v/v) acetonitrile served as mobile phase (300 µL min(-1)). Hyoscyamines were detected in the positive multiple reaction monitor mode. The enantioselective assay was applied to the analysis of atropine degradation in diluted rabbit serum in vitro as well as to human in vivo plasma samples from a pesticide-poisoned patient treated with atropine.