Operational evaluation of three commercial configurations of atropine/HI-6 wet/dry autoinjectors

Oxidative stress status assessment of rats' brains injury following subacute exposure to K-oximes

Oxidative stress status and morphological injuries in the brain of Wistar rats induced by repeated application of selected acetylcholinesterase reactivators - asoxime, obidoxime, K027, K048, K074, and K075 were evaluated. Each oxime in a dose of 0.1 of LD50/kg im was given 2x/week for 4 weeks. Markers of lipid peroxidation (malondialdehyde, MDA), and protein oxidation (advanced oxidation protein products, AOPP), as well as the activity of antioxidant enzymes (catalase, CAT, superoxide dismutase, SOD, glutathione reductase, GR, and glutathione peroxidase, GPx), were estimated in the brain tissue homogenates on day 35 of the study. Brain alterations were carefully quantified by semiquantitative grading scales - brain damage score (BDS). Oxidative stress parameters, MDA and AOPP were significantly highest in the asoxime-, obidoxime- and K075-treated groups (p < 0.001). The activity of SOD and CAT was significantly elevated in the obidoxime-, K048-, and K075-treated groups (p < 0.001). Besides, GR was markedly decreased in the obidoxime- and K074-treated groups (p < 0.01), while treatment with K048, K074 and K075 induced extremely high elevation in GPx levels (p < 0.001). In the same groups of rats, brain alterations associated with polymorphonuclear cell infiltrate were significantly more severe than those observed in animals receiving only asoxime or K027 (p < 0.001). The presented results confirmed that treatment with different oximes significantly improved the oxidative status and attenuated signs of inflammation in rats' brains. Presented results, together with our previously published data can help to predict likely adverse systemic toxic effects, and target organ systems, which are crucial for establishing risk categories, as well as in dose selection of K-oximes as drug candidates.

Autoinjector device for rapid administration of drugs and antidotes in emergency situations and in mass casualty management

There are several situations such as medical emergencies and incidents involving mass casualties where drugs and antidotes have to be administered immediately along with other first aid at the site of the event. Self-administration by the affected person or by a companion is required as a life-saving measure. Autoinjector devices (AIDs) are useful for the rapid administration of drugs and antidotes and they can also be used by those who have not been medically trained. This makes them very convenient for emergency and mass casualty management. An AID has a drug cartridge with an embedded needle for subcutaneous or intramuscular injection, which is usually painless. The drugs are delivered slowly by the AID across a large area in the muscle, which increases the absorption and the drug effects are equal to that of intravenous administration. A variety of AIDs are available, such as atropine and pralidoxime for nerve agent poisoning, epinephrine for anaphylactic shock and allergy, diazepam for seizures, sumatriptan for migraine, amikacin for antibacterial treatment, buprenorphine for pain relief and monoclonal antibodies for a variety of diseases. This review describes the published peer-reviewed literature identified by online searches of journal databases.

Interspecies and intergender differences in acute toxicity of K-oximes drug candidates

K-oximes were developed as modern drug candidates acting as AChE reactivators. In this study, it has been investigated which interspecies and intergender differences changes could be observed in Wistar rats and Swiss mice, both genders, after the treatment with increasing doses of selected acetylcholinesterase reactivators - asoxime, obidoxime, K027, K048, and K075. After the 24 h, a number of died animals was counted and the median lethal dose (LD₅₀) for each oxime was calculated. By using the intramuscular route of administration, asoxime and K027 had the least toxicity in female rats (640.21 mg/kg and 686.08 mg/kg), and in female mice (565.75 mg/kg and 565.74 mg/kg), respectively. Moreover, asoxime and K027 showed 3, 4 or 8 times less acute toxicity in comparison to K048, obidoxime and K075, respectively. Beyond, K075 had the greatest toxicity in male rats (81.53 mg/kg), and in male mice (57.34 mg/kg), respectively. Our results can help to predict likely adverse toxic effects, target organ systems and possible outcome in the event of massive human overexposure, and in establishing risk categories or in dose selection for the initial repeated dose toxicity tests to be conducted for each oxime.

Toxic Injury to Muscle Tissue of Rats Following Acute Oximes Exposure

Therapeutic application of newly developed oximes is limited due to their adverse effects on different tissues. Within this article, it has been investigated which morphological changes could be observed in Wistar rats after the treatment with increasing doses of selected acetyl cholinesterase reactivators - asoxime, obidoxime, K027, K048, and K075. Subsequently, heart, diaphragm and musculus popliteus were obtained for pathohistological and semiquantitative analysis 24 hrs and 7 days after im administration of a single dose of 0.1 LD₅₀, 0.5 LD₅₀, and 1.0 LD₅₀ of each oxime. Different muscle damage score was based on an estimation scale from 0 (no damage) to 5 (strong damage). In rats treated with 0.1 LD₅₀ of each oxime, muscle fibres did not show any change. The intensive degeneration was found in all muscles after treatment with 0.5 LD₅₀ of asoxime and obidoxime, respectively. Acute toxic muscle injury was developed within 7 days following treatment with 0.5 LD₅₀ and 1.0 LD₅₀ of each oxime, with the highest values in K048 and K075 group (P < 0.001 vs. control and asoxime), respectively. The early muscle alterations observed in our study seem to contribute to the pathogenesis of the oxime-induced toxic muscle injury, which probably manifests as necrosis and/or inflammation.

Medical management of incidents with chemical warfare agents

Successful management of incidents with chemical warfare agents strongly depends on the speed of medical help and the ability of helpers to react properly. Though the general principles of clinical toxicology, such as decontamination, stabilization, patient evaluation and symptomatic treatment are similar for many toxicants, chemical warfare agents deserve special attention because of their very high inhalative and cutaneous toxicity, rapid onset of the disease and multiple organ failures. This article describes the medical management of mass casualties with blister agents, nerve agents and blood agents from the viewpoint of a clinical toxicologist. Characteristic diagnostic signs, decontamination procedures and therapeutic schemes for these agents are described. Treatment options are discussed. The importance of planning (e.g. antidote availability) and preparedness is emphasized.

The role of oximes in the management of organophosphorus pesticide poisoning

The number of intoxications with organophosphorus pesticides (OPs) is estimated at some 3,000,000 per year, and the number of deaths and casualties some 300,000 per year. OPs act primarily by inhibiting acetylcholinesterase (AChE), thereby allowing acetylcholine to accumulate at cholinergic synapses, disturbing transmission at parasympathetic nerve endings, sympathetic ganglia, neuromuscular endplates and certain CNS regions. Atropine is the mainstay of treatment of effects mediated by muscarine sensitive receptors; however, atropine is ineffective at the nicotine sensitive synapses. At both receptor types, reactivation of inhibited AChE may improve the clinical picture. The value of oximes, however, is still a matter of controversy. Enthusiastic reports of outstanding antidotal effectiveness, substantiated by laboratory findings of reactivated AChE and improved neuromuscular transmission, contrast with many reports of disappointing results. In vitro studies with human erythrocyte AChE, which is derived from the same single gene as synaptic AChE, revealed marked differences in the potency and efficacy of pralidoxime, obidoxime, HI 6 and HLö 7, the latter two oximes being considered particularly effective in nerve agent poisoning. Moreover, remarkable species differences in the susceptibility to oximes were revealed, requiring caution when animal data are extrapolated to humans. These studies impressively demonstrated that any generalisation regarding an effective oxime concentration is inappropriate. Hence, the 4 mg/L concept should be dismissed. To antagonise the toxic effects of the most frequently used OPs, pralidoxime plasma concentrations of around 80 mumol/L (13.8 mg/L pralidoxime chloride) should be attained while obidoxime plasma concentrations of 10 mumol/L (3.6 mg/L obidoxime chloride) may be sufficient. These concentrations should be maintained as long as circulating poison is expected to be present, which may require oxime therapy for up to 10 days. Various dosage regimens exist to reach this goal. The most appropriate consists of a bolus short infusion followed by a maintenance dosage. For pralidoxime chloride, a 1 g bolus over 30 minutes followed by an infusion of 0.5 g/h appears appropriate to maintain the target concentrtion of about 13 mg/L (70 kg person). For obidoxime chloride, the appropriate dosage is a 0.25 g bolus followed by an infusion of 0.75 g/24 h. These concentrations are well tolerated and keep a good portion of AChE in the active state, thereby retarding the AChE aging rate. AChE aging is particularly rapid with dimethyl phosphoryl compounds and may thwart the effective reactivation by oximes, particularly in suicidal poisoning with excessive doses. In contrast, patients with diethyl OP poisoning may particularly benefit from oxime therapy, even if no improvement is seen during the first days when the poison load is high. The low propensity to aging with diethyl OP poisoning may allow reactivation after several days, when the poison concentration drops. Rigorous testing of the benefits of oximes is only possible in randomised controlled trials with clear stratification according to the class of pesticides involved, time elapsed between exposure and treatment and severity of cholinergic symptoms on admission.

Stability study of a new antidote drug combination (Atropine-HI-6-Prodiazepam) for treatment of organophosphate poisoning

The main purpose of this study was to investigate the chemical stability of a new antidote combination for the treatment of organophosphate poisoning. The antidote combination was packed (enclosed) in two plastic compartments separated by a barrier film. One of them contained a powder oxime cholinesterase reactivator (HI-6-monohydrate 1-[[[4-(aminocarbonyl)pyridinio]methoxy]methyl]-2-[(hydro xyimino)meth yl]-pyridinium dichloride). The other contained an anticholinergic (Atropine) and an anticonvulsant (Prodiazepam or Avizafone (L-lysyl-N-(2-benzoyl-4-chlorophenyl)-N-methyl-glycinamide dihydrochloride) drug in a liquid mixture. The plastic compartments were mounted in an autoinjector device to study the dissolution of HI-6 by ejection of the solution. Drug analysis was performed by high-performance liquid chromatography. The results obtained after 6 months show that this new antidote combination is stable. The amount of each antidote is unchanged during the study. Some known degradation products can be detected in small amounts. The autoinjector mechanism used, gives a complete dissolution of HI-6 powder in the liquid mixture throughout the study.

Review of oximes available for treatment of nerve agent poisoning

A review was conducted of papers describing the use of N-methyl-2-pyridinealdoxime (PAM), toxogonin or HI-6 as antidotes to the nerve agents tabun, sarin, soman and VX. The review included use of the oxime alone, oxime plus atropine and oxime plus atropine plus diazepam, given therapeutically, i.e. after nerve agent, in all cases. Experiments with any of these compounds given prophylactically were not considered. The review also included protocols of pyridostigmine prophylaxis and oxime-atropine therapy (with or without diazepam). It was difficult to draw conclusions as to the best oxime to use, because of lack of data in many cases. The identity of the oxime did not appear to be important when pyridostigmine prophylaxis was combined with atropine-oxime-diazepam therapy; in these cases, very good protection was observed in guinea pigs against all four nerve agents. The choice of oxime based on the data presently available may well depend on factors other than protection against lethality, such as cost and availability of the oxime and human toxicity of the oxime. This last factor was also reviewed, and the results showed that toxogonin is likely to cause more side-effects than PAM or HI-6. The efficacy of the oximes against the emerging threat agent GF was also reviewed.

Pharmacokinetics of the oximes HI 6 and HLö 7 in dogs after i.m. injection with newly developed dry/wet autoinjectors

The rapid onset of cholinergic crisis after intoxication with highly toxic organophosphorus compounds calls for pre-clinical administration of effective antidotes as early as possible. For this purpose, i.m. administration of the antidotes by autoinjectors is desired to allow early treatment also in the absence of a physician. Besides atropine, oximes with broad antidotal spectrum are considered valuable adjuncts that should be included in antidotal mixtures. To circumvent the problem of limited stability of the new-generation oximes, dry/wet autoinjectors were developed in which the unstable solid is dissolved by a diluent in an adjacent chamber upon activation of the device. In this study the tolerance, bioavailability and pharmacokinetics of 500 mg HI 6 [1-(((4-(aminocarbonyl) pyridinio)methoxy) methyl)-2-((hydroxyimino)methyl) pyridinium dichloride monohydrate] or 200 mg HLö 7 [1-(((4-(aminocarbonyl) pyridinio)methoxy)methyl)-2,4- bis((hydroxyimino)methyl)pyridinium dimethanesulfonate] in combination with 2 mg atropine sulfate versus atropine alone, delivered by two dry/wet autoinjector types, were investigated in eight male beagle dogs (16 kg) in a complete cross-over design. The dogs tolerated the six injections with 3-week intervals without any symptoms of discomfort. Nonetheless, CPK activity increased, peaking at 6 h after injection. In contrast to atropine which merely led to a marginal increase, HI 6 plus atropine increased the baseline CPK activity about 10-fold, and HLö 7 plus atropine about 20-fold, regardless of the injector type. The HI 6 autoinjectors from Astra Tech were from an irregular production batch which did not deliver the declared HI 6 dose. The HLö 7 autoinjectors from Astra Tech and both Binaject autoinjectors from STI functioned well: the bioavailability was complete with tmax values of about 25 min as observed after conventional i.m. injection. The absorption half-time was about 8 min, elimination t1/2 about 50 min, and Vapp 0.26 l/kg. The urinary recovery of unchanged oximes was 70-80%, the renal clearance being the same as for inulin. Unexpectedly, hematocrit and hemoglobin content of blood decreased by about 15% within 2 h and reached pre-treatment values after 6-24 h. This decrease was observed with all three drug treatments and could not be accounted for by blood loss (< 4%), thus pointing to an atropine effect. In conclusion, the newly developed dry/wet autoinjectors appear suitable for the administration of atropine and an oxime stored in solid form.

Simple high-performance liquid chromatographic method for assessing the deterioration of atropine-oxime mixtures employed as antidotes in the treatment of nerve agent poisoning

A set of reversed-phase HPLC conditions for determining the degradation of atropine and the oxime (pralidoxime, obidoxime, or HI-6) in autoinjectors designed for use against nerve agent poisoning is described. The assay conditions for atropine do not require its prior separation from the large molar excess of oxime since both the atropine and tropic acid peaks elute well clear of the oxime and its degradation products and the phenolic preservatives. Further dilution of the sample and simple changes to the mobile phase then provide conditions for the oxime and its major degradation products to be quantitated.

Efficacy of HLö-7 and pyrimidoxime as antidotes of nerve agent poisoning in mice

The toxicity and efficacy of two oximes, HLö-7 and pyrimidoxime, were evaluated in mice and compared to those obtained with HI-6. HLö-7 and pyrimidoxime produced 24 h LD50 values of 356 and 291 mg/kg (i.p.), respectively. In combination with atropine (17.4 mg/kg, i.p.), HLö-7 was a very efficient therapy against poisoning by 3 x LD50 dose of soman, sarin and GF and 2 x LD50 dose of tabun with ED50 values of 12.4, 0.31, 0.32 and 25.2 mg/kg, respectively. In contrast, pyrimidoxime was a relatively poor therapy which resulted in ED50 values of greater than 150, 5.88, 100 and 71 mg/kg against poisoning by soman, sarin, GF and tabun, respectively. HLö-7 produced significant (p less than 0.05) reactivation of phosphorylated acetylcholinesterase, in vivo, resulting in 47, 38, 27 and 10% reactivation of sarin, GF, soman and tabun inhibited mouse diaphragm acetylcholinesterase, respectively. HLö-7 also antagonized sarin-induced hypothermia in mice suggesting that it reactivated central acetylcholinesterase. The potential of HLö-7 as a replacement oxime for the treatment of nerve agent poisoning is discussed.