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Corticosteroids in ophthalmology: drug delivery innovations, pharmacology, clinical applications, and future perspectives. Drug Deliv Transl Res 2020; 11:866-893. [PMID: 32901367 DOI: 10.1007/s13346-020-00843-z] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Corticosteroids remain the mainstay of the treatment for various ocular conditions affecting the ocular surface, anterior and posterior segments of the eye due to their anti-inflammatory, anti-oedematous, and anti-neovascularization properties. Prednisolone, prednisolone acetate, dexamethasone, triamcinolone acetonide, fluocinolone acetonide, and loteprednol etabonate are amongst the most widely used ophthalmic corticosteroids. Corticosteroids differ in their activity and potency in the eye due to their inherent pharmacological and pharmaceutical differences. Different routes and regimens are available for ocular administration of corticosteroids. Conventional topical application to the eye is the route of choice when targeting diseases affecting the ocular surface and anterior segment, while periocular, intravitreal, and suprachoroidal injections can be potentially effective for posterior segment diseases. Corticosteroid-induced intraocular pressure elevation and cataract formation remain the most significant local risks following topical as well as systemic corticosteroid administration. Invasive drug administration via intracameral, subconjunctival, and intravitreal injection can enhance ocular bioavailability and minimize dose and dosing frequency of administration, yet may exacerbate ocular side effects of corticosteroids. This review provides a critical appraisal of the ophthalmic uses of corticosteroid, routes of administration, drug delivery fundamentals and novel ocular implantable steroid delivery systems, factors influencing side effects, and future perspectives for ocular corticosteroid therapy.
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Chambers JE, Dail MB, Meek EC. Oxime-mediated reactivation of organophosphate-inhibited acetylcholinesterase with emphasis on centrally-active oximes. Neuropharmacology 2020; 175:108201. [PMID: 32544483 DOI: 10.1016/j.neuropharm.2020.108201] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/02/2020] [Accepted: 06/11/2020] [Indexed: 01/25/2023]
Abstract
This review provides an overview of the global research leading to the large number of compounds developed as reactivators of acetylcholinesterase inhibited by a variety of organophosphate compounds, most of which are nerve agents but also some insecticides. A number of these organophosphates are highly toxic and effective therapy by reactivators contributes to saving lives. Two major challenges for more effective therapy with reactivators are identification of a broad spectrum reactivator efficacious against a variety of organophosphate structures, and a reactivator that can cross the blood-brain barrier to protect the brain. The most effective of the reactivators developed are the nucleophilic pyridinium oximes, which bear a permanent positive charge from the quaternary nitrogen in the pyridinium ring. The permanent positive charge retards the oximes from crossing the blood-brain barrier and therefore restoration of normal cholinergic function in the brain is unlikely. A number of laboratories have developed nucleophiles, mostly oximes, that are theorized to cross the blood-brain barrier by several strategies. At the present time, no reactivator is optimally broad spectrum across the wide group of organophosphate chemistries. Some oximes, including the substituted phenoxyalkyl pyridinium oximes invented by our laboratories, have the potential to provide neuroprotection in the brain and show evidence of efficacy against both nerve agent and insecticidal chemistries, so these novel oximes have promise for future development. This article is part of the special issue entitled 'Acetylcholinesterase Inhibitors: From Bench to Bedside to Battlefield'.
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Affiliation(s)
- Janice E Chambers
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, 39762-6100, USA.
| | - Mary B Dail
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, 39762-6100, USA
| | - Edward C Meek
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, 39762-6100, USA
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Chambers JE, Meek EC. Central neuroprotection demonstrated by novel oxime countermeasures to nerve agent surrogates. Ann N Y Acad Sci 2020; 1479:5-12. [PMID: 32319115 DOI: 10.1111/nyas.14352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 03/20/2020] [Accepted: 03/26/2020] [Indexed: 01/09/2023]
Abstract
Oximes remain a long-standing element of the therapy for nerve agents, organophosphates (OPs) that poison by inhibiting the enzyme acetylcholinesterase (AChE), resulting in hypercholinergic activity both centrally and peripherally. Oximes, such as the pyridinium oxime pralidoxime (2-PAM) in the United States, can reactivate the inhibited AChE and restore cholinergic function. However, there are several drawbacks to the current oximes; one of them, the inability of these oximes to effectively enter the brain, is the subject of study by several laboratories, including ours. Our laboratory invented a platform of substituted phenoxyalkyl pyridinium oximes that were tested against highly relevant surrogates of the nerve agents, sarin and VX. Using high sublethal dosages of the OPs, the novel oximes were observed to attenuate seizure-like behavior in rats and to reduce the levels of glial fibrillary acidic protein (an indicator of glial scarring) to control levels, in contrast to levels observed with 2-PAM or no oxime therapy. Using lethal levels of surrogates, some novel oximes protected against lethality compared with 2-PAM, shortened the time to cessation of seizure-like behavior (from 8+ to 6 h), and protected the brain neurons. Therefore, some of these novel oximes are showing exceptional promise alone or in combination with 2-PAM as therapeutics against nerve agent toxicity.
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Affiliation(s)
- Janice E Chambers
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi
| | - Edward C Meek
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi
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Franjesevic AJ, Sillart SB, Beck JM, Vyas S, Callam CS, Hadad CM. Resurrection and Reactivation of Acetylcholinesterase and Butyrylcholinesterase. Chemistry 2019; 25:5337-5371. [PMID: 30444932 PMCID: PMC6508893 DOI: 10.1002/chem.201805075] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/15/2018] [Indexed: 01/10/2023]
Abstract
Organophosphorus (OP) nerve agents and pesticides present significant threats to civilian and military populations. OP compounds include the nefarious G and V chemical nerve agents, but more commonly, civilians are exposed to less toxic OP pesticides, resulting in the same negative toxicological effects and thousands of deaths on an annual basis. After decades of research, no new therapeutics have been realized since the mid-1900s. Upon phosphylation of the catalytic serine residue, a process known as inhibition, there is an accumulation of acetylcholine (ACh) in the brain synapses and neuromuscular junctions, leading to a cholinergic crisis and eventually death. Oxime nucleophiles can reactivate select OP-inhibited acetylcholinesterase (AChE). Yet, the fields of reactivation of AChE and butyrylcholinesterase encounter additional challenges as broad-spectrum reactivation of either enzyme is difficult. Additional problems include the ability to cross the blood brain barrier (BBB) and to provide therapy in the central nervous system. Yet another complication arises in a competitive reaction, known as aging, whereby OP-inhibited AChE is converted to an inactive form, which until very recently, had been impossible to reverse to an active, functional form. Evaluations of uncharged oximes and other neutral nucleophiles have been made. Non-oxime reactivators, such as aromatic general bases and Mannich bases, have been developed. The issue of aging, which generates an anionic phosphylated serine residue, has been historically recalcitrant to recovery by any therapeutic approach-that is, until earlier this year. Mannich bases not only serve as reactivators of OP-inhibited AChE, but this class of compounds can also recover activity from the aged form of AChE, a process referred to as resurrection. This review covers the modern efforts to address all of these issues and notes the complexities of therapeutic development along these different lines of research.
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Affiliation(s)
- Andrew J Franjesevic
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Sydney B Sillart
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Jeremy M Beck
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Shubham Vyas
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
- Current Address: Department of Chemistry, Colorado School of Mines, 1500 Illinois St., Golden, CO, 80401, USA
| | - Christopher S Callam
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
| | - Christopher M Hadad
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Ave, Columbus, OH, 43210, USA
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Neumann KD, Blecha JE, Hayes TR, Huynh T, Chao CK, Guilloteau N, Zinn KR, VanBrocklin HF, Thompson CM, Gerdes JM. Radiosynthesis, ex Vivo Biodistribution, and in Vivo Positron Emission Tomography Imaging Evaluations of [ 11C]2-Pyridinealdoxime Methiodide ([ 11C]2-PAM): A First-In-Class Antidote Tracer for Organophosphate Intoxication. ACS Chem Neurosci 2018; 9:3007-3014. [PMID: 30071719 DOI: 10.1021/acschemneuro.8b00212] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
2-Pyridinealdoxime methiodide (2-PAM) is a widely used antidote for the treatment of organophosphorus (OP) exposure that reactivates the target protein acetylcholinesterase. Carbon-11 2-PAM was prepared to more fully understand the in vivo mode of action, distribution, and dynamic qualities of this important countermeasure. Alkylation of 2-pyridinealdoxime with [11C]CH3I provided the first-in-class [11C]2-PAM tracer in 3.5% decay corrected radiochemical yield from [11C]CH3I, >99% radiochemical purity, and 4831 Ci/mmol molar activity. [11C]2-PAM tracer distribution was evaluated by ex vivo biodistribution and in vivo dynamic positron emission tomography (PET) imaging in naïve (OP exposure deficient) rats. Tracer alone and tracer coinjected with a body mass-scaled human therapeutic dose of 30 mg/kg nonradioactive 2-PAM demonstrated statistically similar tissue and blood distribution profiles with the greatest uptake in kidney and significantly lower levels in liver, heart, and lung with lesser amounts in blood and brain. The imaging and biodistribution data show that radioactivity uptake in brain and peripheral organs is rapid and characterized by differential tissue radioactivity washout profiles. Analysis of arterial blood samples taken 5 min after injection showed ∼82% parent [11C]2-PAM tracer. The imaging and biodistribution data are now established, enabling future comparisons to outcomes acquired in OP intoxicated rodent models.
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Affiliation(s)
- Kiel D. Neumann
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California 94143, United States
| | - Joseph E. Blecha
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California 94143, United States
| | - Thomas R. Hayes
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California 94143, United States
| | - Tony Huynh
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California 94143, United States
| | - Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
| | - Nicolas Guilloteau
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
| | - Kurt R. Zinn
- Departments of Radiology and Biomedical Engineering, Michigan State University, East Lansing, Michigan 48824, United States
| | - Henry F. VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California 94143, United States
| | - Charles M. Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
| | - John M. Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
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Katz FS, Pecic S, Schneider L, Zhu Z, Hastings-Robinson A, Luzac M, Macdonald J, Landry DW, Stojanovic MN. New therapeutic approaches and novel alternatives for organophosphate toxicity. Toxicol Lett 2018; 291:1-10. [PMID: 29614332 DOI: 10.1016/j.toxlet.2018.03.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/18/2018] [Accepted: 03/26/2018] [Indexed: 10/17/2022]
Abstract
Organophosphate compounds (OPCs) are commonly used as pesticides and were developed as nerve agents for chemical warfare. Exposure to OPCs results in toxicity due to their covalent binding and inhibition of acetylcholinesterase (AChE). Treatment for toxicity due to OPC exposure has been largely focused on the reactivation of AChE by oxime-based compounds via direct nucleophilic attack on the phosphorous center. However, due to the disadvantages to existing oxime-based reactivators for treatment of OPC poisoning, we considered non-oxime mechanisms of reactivation. A high throughput screen of compound libraries was performed to discover previously unidentified reactivation compounds, followed by studies on their analogs. In the process, we discovered multiple non-oxime classes of compounds, the most robust of which we have already reported [1]. Herein, we report other classes of compounds we identified in our screen that are efficient at reactivation. During biochemical characterization, we also found some compounds with other activities that may inspire novel therapeutic approaches to OPC toxicity. Specifically, we found compounds that [1] increase the rate of substrate hydrolysis by AChE and, [2] protect the enzyme from inhibition by OPC. Further, we discovered that a subset of reactivator compounds recover activity from both AChE and the related enzyme butyrylcholinesterase (BuChE). We now report these compounds, their activities and discuss how each relates to therapeutic approaches that would provide alternatives to traditional oxime-based reactivation.
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Affiliation(s)
- Francine S Katz
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA.
| | - Stevan Pecic
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA.
| | - Laura Schneider
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA
| | - Zhengxiang Zhu
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA
| | - Ashley Hastings-Robinson
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA
| | - Michal Luzac
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA
| | - Joanne Macdonald
- Genecology Research Centre, Inflammation and Healing Research Cluster, School of Science and Engineering, University of the Sunshine Coast, 90 Sippy Downs Drive Sippy Downs, QLD 4556, Australia
| | - Donald W Landry
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA
| | - Milan N Stojanovic
- Department of Medicine, Columbia University, 630 W 168th Street, BB8-444, New York, NY, 10032, USA
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Comstock TL, Sheppard JD. Loteprednol etabonate for inflammatory conditions of the anterior segment of the eye: twenty years of clinical experience with a retrometabolically designed corticosteroid. Expert Opin Pharmacother 2018; 19:337-353. [PMID: 29430976 DOI: 10.1080/14656566.2018.1439920] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
INTRODUCTION Topical corticosteroids are an important pharmacotherapy for the management of various inflammatory conditions affecting the anterior segment of the eye. However, medications in this class are associated with well-known risks including increased intraocular pressure (IOP) and development of cataracts. The topical corticosteroid loteprednol etabonate (LE) was developed with the specific intention of minimizing these side effects. AREAS COVERED The focus of this review is to examine published efficacy and safety data for LE, a drug engineered to undergo rapid metabolism to inactive metabolites with the goal of improved safety. Two decades of clinical research focused on LE formulations are reviewed, including the use of LE in combination with tobramycin. The cumulative body of experience affirms the concept that the molecular design of LE confers certain safety benefits without compromising the desired anti-inflammatory efficacy of a topical corticosteroid. EXPERT OPINION Loteprednol etabonate is a mainstay for topical therapy of a wide variety of commonplace and niche conditions of the ocular surface and the anterior segment, including in the healing post-operative patient. Its versatility and safety allow eye care providers to recommend both acute induction as well as chronic maintenance therapy with appropriate follow-up.
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Affiliation(s)
| | - John D Sheppard
- b Virginia Eye Consultants , Norfolk , VA , USA.,c Eastern Virginia Medical School , Norfolk , VA , USA
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Wei Z, Liu YQ, Wang SZ, Yao L, Nie HF, Wang YA, Liu XY, Zheng ZB, Li S. Conjugates of salicylaldoximes and peripheral site ligands: Novel efficient nonquaternary reactivators for nerve agent-inhibited acetylcholinesterase. Bioorg Med Chem 2017; 25:4497-4505. [DOI: 10.1016/j.bmc.2017.06.041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 06/13/2017] [Accepted: 06/25/2017] [Indexed: 10/19/2022]
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Buchwald P, Bodor N. Brain-Targeting Chemical Delivery Systems and Their Cyclodextrin-Based Formulations in Light of the Contributions of Marcus E. Brewster. J Pharm Sci 2016; 105:2589-2600. [DOI: 10.1016/j.xphs.2016.04.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 04/07/2016] [Accepted: 04/07/2016] [Indexed: 11/29/2022]
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Bhattacharjee AK, Marek E, Le HT, Ratcliffe R, DeMar JC, Pervitsky D, Gordon RK. Discovery of non-oxime reactivators using an in silico pharmacophore model of reactivators for DFP-inhibited acetylcholinesterase. Eur J Med Chem 2015; 90:209-20. [DOI: 10.1016/j.ejmech.2014.11.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 11/03/2014] [Accepted: 11/05/2014] [Indexed: 10/24/2022]
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Voicu V, Rădulescu FŞ, Medvedovici A. Relationships between the antidotal efficacy and structure, PK/PD parameters and bio-relevant molecular descriptors of AChE reactivating oximes: inclusion and integration to biopharmaceutical classification systems. Expert Opin Drug Metab Toxicol 2014; 11:95-109. [DOI: 10.1517/17425255.2015.980813] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Victor Voicu
- 1Romanian Academy, Medical Sciences Section, Calea Victoriei no. 125, Bucharest – 010071, Romania
- 2University of Medicine and Pharmacy “Carol Davila”, Faculty of Medicine, Department of Clinical Pharmacology, Toxicology and Psychopharmacology, Şcoala Floreasca Street no. 8, Bucharest - 011643, Romania
| | - Flavian Ştefan Rădulescu
- 3University of Medicine and Pharmacy “Carol Davila”, Faculty of Pharmacy, Department of Drug Industry and Pharmaceutical Biotechnology, Traian Vuia Street no. 6, Bucharest-020956, Romania
| | - Andrei Medvedovici
- 4University of Bucharest, Faculty of Chemistry, Department of Analytical Chemistry, Panduri Ave., no. 90, Bucharest- 050663, Romania
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Petroianu GA. Oxime treatment for organophosphorus compound exposure: Getting it (into the brain) might not be that good for you, after all. J Appl Biomed 2014. [DOI: 10.1016/j.jab.2014.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Petroianu GA, Athauda G, Darvas F, Kalasz H, Lorke DE. K-OXIME (K-27): PHOSPHYLATION-INDUCED CHANGES IN LOGP. ACTA ACUST UNITED AC 2014. [DOI: 10.31482/mmsl.2014.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Advances in corticosteroid therapy for ocular inflammation: loteprednol etabonate. Int J Inflam 2012; 2012:789623. [PMID: 22536546 PMCID: PMC3321285 DOI: 10.1155/2012/789623] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 11/22/2011] [Indexed: 12/05/2022] Open
Abstract
Topical corticosteroids are effective in reducing anterior segment inflammation but are associated with adverse drug reactions (ADRs) including elevation of intraocular pressure (IOP) and cataract formation. Retrometabolic drug design has advanced the development of new corticosteroids with improved therapeutic indices. Engineered from prednisolone, loteprednol etabonate (LE) has a 17α-chloromethyl ester, in lieu of a ketone group, and a 17β-etabonate group. LE is highly lipophilic and binds with high affinity to the glucocorticoid receptor; any unbound LE is metabolized to inactive metabolites. LE has been studied in several anterior segment inflammatory conditions (giant papillary conjunctivitis, allergic conjunctivitis, anterior uveitis, and keratoconjunctivitis sicca), and in postoperative ocular inflammation and pain. Combined with tobramycin, it is effective in blepharokeratoconjunctivitis. Elevations in IOP are infrequent with LE, and the absence of a C-20 ketone precludes formation of Schiff base intermediates with lens proteins, a common first step implicated in cataract formation with ketone steroids.
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Discovery of non-oxime reactivators using an in silico pharmacophore model of oxime reactivators of OP-inhibited acetylcholinesterase. Eur J Med Chem 2012; 49:229-38. [DOI: 10.1016/j.ejmech.2012.01.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 12/26/2011] [Accepted: 01/07/2012] [Indexed: 11/30/2022]
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Khan FA, Campbell AJ, Hoyt B, Herdman C, Ku T, Thangavelu S, Gordon RK. Oxidative mechanisms for the biotransformation of 1-methyl-1,6-dihydropyridine-2-carbaldoxime to pralidoxime chloride. Life Sci 2011; 89:911-7. [PMID: 21989207 DOI: 10.1016/j.lfs.2011.09.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 08/02/2011] [Accepted: 09/13/2011] [Indexed: 01/02/2023]
Abstract
AIMS Due to pralidoxime chloride's (2-PAM) positive charge, it's penetration through the blood brain barrier (BBB) and reactivation of organophosphate (OP) inhibited central nervous system (CNS) acetylcholinesterase (AChE) is poor. The results of CNS inhibited AChE are seizures. Pro-2-PAM (1-methyl-1,6-dihydropyridine-2-carbaldoxime), a pro-drug of 2-PAM, due to higher hydrophobicity, penetrates the BBB better but must be oxidized to 2-PAM, the active form of the oxime to reactivate CNS AChE in order to abrogate seizures. In this study, we characterize the in vivo mechanism of pro-2-PAM oxidation. MAIN METHODS A high pressure liquid chromatography (HPLC) assay was developed to quantify the conversion of pro-2-PAM to 2-PAM. NADPH oxidase activity was measured by a photo-luminescence assay using lucigenin substrate. Upon analysis, the rate of NADPH induced oxidation suggested that an alternate mechanism may be involved. Therefore, various enzyme co-factors of oxidation-reduction enzyme systems were evaluated, including nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide phosphate (NADP), flavin adenine dinucleotide (FAD), riboflavin 5'-phosphate (FMN), and riboflavin. Next, a spectrophotometric assay was developed to measure the conversion of pro-2-PAM to 2-PAM in the presence of riboflavin. KEY FINDINGS In guinea pig brain homogenate, diphenyleneiodonium (DPI), a specific NADPH oxidase inhibitor, reduced pro-2-PAM to 2-PAM conversion to less than 25%. In contrast, riboflavin, FAD, and FMN rapidly oxidized all pro-2-PAM to 2-PAM in an in vitro assay. Riboflavin oxidized pro-2-PAM reactivated diisopropylfluorophosphate (DFP) inhibited AChE. SIGNIFICANCE The present study shows that pro-2-PAM was rapidly oxidized by riboflavin to 2-PAM, which reactivated organophosphate (OP)-inhibited AChE.
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Affiliation(s)
- Farhat A Khan
- Department of Regulated Laboratories, Division of Regulated Activities, Silver Spring, MD 20910, United States.
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Kalisiak J, Ralph EC, Zhang J, Cashman JR. Amidine-oximes: reactivators for organophosphate exposure. J Med Chem 2011; 54:3319-30. [PMID: 21438612 DOI: 10.1021/jm200054r] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new class of amidine-oxime reactivators of organophosphate (OP)-inhibited cholinesterases (ChE) were designed, synthesized, and tested. These compounds represent a novel group of oximes with enhanced capabilities of crossing the blood-brain barrier. Lack of brain penetration is a major limitation for currently used oximes as antidotes of OP poisoning. The concept described herein relies on a combination of an amidine residue and oxime functionality whereby the amidine increases the binding affinity to the ChE and the oxime is responsible for reactivation. Amidine-oximes were tested in vitro and reactivation rates for OP-BuChE were greater than pralidoxime (2-PAM) or monoisonitrosoacetone (MINA). Amidine-oxime reactivation rates for OP-AChE were lower compared to 2-PAM but greater compared with MINA. After pretreatment for 30 min with oximes 15c and 15d (145 μmol/kg, ip) mice were challenged with a soman model compound. In addition, 15d was tested in a post-treatment experiment (145 μmol/kg, ip, administration 5 min after sarin model compound exposure). In both cases, amidine-oximes afforded 100% 24 h survival in an animal model of OP exposure.
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Affiliation(s)
- Jarosław Kalisiak
- Human BioMolecular Research Institute, 5310 Eastgate Mall, San Diego, California 92121, United States.
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Shih TM, Guarisco JA, Myers TM, Kan RK, McDonough JH. The oxime pro-2-PAM provides minimal protection against the CNS effects of the nerve agents sarin, cyclosarin, and VX in guinea pigs. Toxicol Mech Methods 2010; 21:53-62. [DOI: 10.3109/15376516.2010.529190] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Dos Santos AA, Dos Santos DB, Dafre AL, De Bem AF, Souza DO, Da Rocha JBT, Kuca K, Farina M. In vitro Reactivating Effects of Standard and Newly Developed Oximes on Malaoxon-Inhibited Mouse Brain Acetylcholinesterase. Basic Clin Pharmacol Toxicol 2010; 107:768-73. [DOI: 10.1111/j.1742-7843.2010.00576.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Voicu VA, Bajgar J, Medvedovici A, Radulescu FS, Miron DS. Pharmacokinetics and pharmacodynamics of some oximes and associated therapeutic consequences: a critical review. J Appl Toxicol 2010; 30:719-29. [PMID: 20635332 DOI: 10.1002/jat.1561] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 05/21/2010] [Accepted: 05/21/2010] [Indexed: 11/10/2022]
Abstract
Undoubtedly, the use of oximes represents real progress in counteracting intoxications with organophosphates (OP), through potentiating antidotal effects of atropine. The penetration extent of these compounds through the blood-brain barrier (BBB) to significantly reactivate phosphorylated or phosphonylated acetylcholinesterase (AChE) in the brain still remains a debatable issue. Penetration of biological barriers by oximes was investigated mainly through determination of several quantitative parameters characterizing digestive absorption and BBB penetration. A weak penetration of biological barriers could be concluded from the available experimental data. The functional parameters/therapeutic effects following the penetration of oximes through BBB, more precisely the antagonism of OP-induced seizures and hypothermia, prevention of brain damage and respiratory center protection, leading to the final end-point, the survival of intoxicated organisms, are of high interest. It seems obvious that oximes are weakly penetrating the BBB, with minimal brain AChE reactivation (<5%) in important functional areas, such as the ponto-medullar. The cerebral protection achieved through administration of oximes is only partial, without major impact on the antagonism of OP-induced seizures, hypothermia and respiratory center inhibition. The antidotal effects probably result from synergic effects of other PD properties, different from the brain AChE reactivation process. Oxime structures especially designed for enhanced BBB penetration, through potentiating the hydrophobic characteristics, more often produce neurotoxic effects. Certainly, obtaining oximes with broad action spectrum (active against all OP types) would make a sense, but certainly, such a target is not achievable only through the increase in their penetrability in the brain.
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Affiliation(s)
- Victor A Voicu
- University of Medicine and Pharmacy Carol Davila, Clinical Pharmacology, Toxicology and Psychopharmacology, Bucharest, Romania.
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Demar JC, Clarkson ED, Ratcliffe RH, Campbell AJ, Thangavelu SG, Herdman CA, Leader H, Schulz SM, Marek E, Medynets MA, Ku TC, Evans SA, Khan FA, Owens RR, Nambiar MP, Gordon RK. Pro-2-PAM therapy for central and peripheral cholinesterases. Chem Biol Interact 2010; 187:191-8. [PMID: 20156430 DOI: 10.1016/j.cbi.2010.02.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 02/04/2010] [Accepted: 02/09/2010] [Indexed: 11/29/2022]
Abstract
Novel therapeutics to overcome the toxic effects of organophosphorus (OP) chemical agents are needed due to the documented use of OPs in warfare (e.g. 1980-1988 Iran/Iraq war) and terrorism (e.g. 1995 Tokyo subway attacks). Standard OP exposure therapy in the United States consists of atropine sulfate (to block muscarinic receptors), the acetylcholinesterase (AChE) reactivator (oxime) pralidoxime chloride (2-PAM), and a benzodiazepine anticonvulsant to ameliorate seizures. A major disadvantage is that quaternary nitrogen charged oximes, including 2-PAM, do not cross the blood brain barrier (BBB) to treat brain AChE. Therefore, we have synthesized and evaluated pro-2-PAM (a lipid permeable 2-PAM derivative) that can enter the brain and reactivate CNS AChE, preventing seizures in guinea pigs after exposure to OPs. The protective effects of the pro-2-PAM after OP exposure were shown using (a) surgically implanted radiotelemetry probes for electroencephalogram (EEG), (b) neurohistopathology of brain, (c) cholinesterase activities in the PNS and CNS, and (d) survivability. The PNS oxime 2-PAM was ineffective at reducing seizures/status epilepticus (SE) in diisopropylfluorophosphate (DFP)-exposed animals. In contrast, pro-2-PAM significantly suppressed and then eliminated seizure activity. In OP-exposed guinea pigs, there was a significant reduction in neurological damage with pro-2-PAM but not 2-PAM. Distinct regional areas of the brains showed significantly higher AChE activity 1.5h after OP exposure in pro-2-PAM treated animals compared to the 2-PAM treated ones. However, blood and diaphragm showed similar AChE activities in animals treated with either oxime, as both 2-PAM and pro-2-PAM are PNS active oximes. In conclusion, pro-2-PAM can cross the BBB, is rapidly metabolized inside the brain to 2-PAM, and protects against OP-induced SE through restoration of brain AChE activity. Pro-2-PAM represents the first non-invasive means of administering a CNS therapeutic for the deleterious effects of OP poisoning by reactivating CNS AChE.
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Affiliation(s)
- James C Demar
- Walter Reed Army Institute of Research, Division of Regulated Activities, Department of Regulated Laboratories, Silver Spring, MD 20910-7500, United States
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Voicu VA, Thiermann H, RÄdulescu FÅ, Mircioiu C, Miron DS. The Toxicokinetics and Toxicodynamics of Organophosphonatesversusthe Pharmacokinetics and Pharmacodynamics of Oxime Antidotes: Biological Consequences. Basic Clin Pharmacol Toxicol 2010; 106:73-85. [DOI: 10.1111/j.1742-7843.2009.00486.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Gómez E, Miguel M, Jiménez O, de la Rosa G, Lavilla R. 1,4-Dihydropicolinic acid derivatives: novel NADH analogues with an altered connectivity pattern. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.03.069] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
Chemical delivery systems (CDSs) based on the redox conversion of a lipophilic dihydropyridine to an ionic, lipid-insoluble pyridinium salt have been developed to improve the access of therapeutic agents to the central nervous system. A dihydropyridinium-type CDS or a redox analog of the drug is sufficiently lipophilic to enter the brain by passive transport, then undergoes an enzymatic oxidation to an ionic pyridinium compound, which promotes retention in the CNS. At the same time, peripheral elimination of the entity is accelerated due to facile conversion of the CDS in the body. This review discusses chemical, physicochemical, biochemical, and biological aspects in relation to the principles and practical implementation of the redox brain-targeting approach to various classes of drugs. Representative examples to the brain-enhanced delivery of neurotransmitters, steroids, anticonvulsants, antibiotics, antiviral, anticancer and antidementia agents, and neuropeptides and their analogs are presented in detail. In vivo and in vitro studies and preliminary clinical data of several novel derivatives have been promising, which could lead to a practical use of the redox CDSs after proper pharmaceutical development. The investigations accentuate the need for considering physicochemical, metabolic, and pharmacokinetic properties in designing of carrier systems that are able to target drugs into the central nervous system.
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Affiliation(s)
- L Prokai
- Center for Drug Discovery, College of Pharmacy, University of Florida, J. Hillis Miller Health Center, Gainesville, FL 32610, USA.
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Carvalho I, Miller J. SYNTHESIS OF 1-METHYL-2-HYDROXYIMINOMETHYL-ARYL-PYRIDINIUM SALTS WITH POTENTIAL AS ACETYL-CHOLINESTERASE REACTIVATORS. HETEROCYCL COMMUN 1995. [DOI: 10.1515/hc.1995.1.5-6.403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Amsberry KL, Borchardt RT. Amine prodrugs which utilize hydroxy amide lactonization. I. A potential redox-sensitive amide prodrug. Pharm Res 1991; 8:323-30. [PMID: 2052518 DOI: 10.1023/a:1015885213625] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Several amides of 3-(3',6'-dioxo-2',4'-dimethylcyclohexa-1',4'-diene)-3,3- dimethylpropionic acid (2) have been synthesized and tested as model redox-sensitive pro-prodrugs of amines. The reduction of these model pro-prodrugs generated hydroxy amide intermediates 4a-4h, the lactonization of which resulted in amine release. The rates of lactonization of 4a-4h were investigated at pH 7.4 and 37 degrees C. The half-lives for appearance of the product lactone 1a from these intermediates were found to range from 1.4 to 3.4 min. With such rapid lactonization rates, it is believed that reduction will be the rate-limiting step in the two-step conversion of the pro-prodrug to the amine.
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Affiliation(s)
- K L Amsberry
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence 66045
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Murakami T, Shek E, Pop E, Bodor N. Improved anticonvulsant activity of phenytoin by a redox brain delivery system. II: Stability in buffers and biological materials. J Pharm Sci 1989; 78:732-7. [PMID: 2585265 DOI: 10.1002/jps.2600780906] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The stability of nine chemical delivery systems (CDSs) for phenytoin (DPH) was studied in aqueous buffers and in biological materials. The systems were based on a dihydropyridine in equilibrium quaternary pyridinium salt redox pair attached to 3-(hydroxymethyl)phenytoin via an ester linkage. The pyridinium derivatives released DPH in aqueous buffers and their hydrolytic reactivity was consistent with their chemical structure. Although in rat blood and plasma all pyridinium esters hydrolyzed rapidly, there was a wide range in the hydrolysis rates in rat brain homogenate. The sterically hindered 1-alkylcarboxynicotinamide was the least reactive ester (t1/2 = 98.2 min), while the trigonellylglycolate ester was the fastest to hydrolyze enzymatically (t1/2 = 2 min) in rat brain homogenate. In acidic media, the major products of all dihydropyridine esters were the corresponding water adducts, the 6-hydroxy- 1,4,5,6-tetrahydropyridines. These adducts were of no significance in biological materials. After comparison of the relative stability of the corresponding pairs of dihydropyridine and pyridinium ion in brain homogenate and the absolute stability of the various dihydropyridines, two CDSs were chosen for further in vivo evaluations. The CDSs chosen were the dihydrotrigonellinate ester and its 6-methyl derivative.
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Affiliation(s)
- T Murakami
- University of Florida, Center for Drug Design and Delivery, Gainesville 32610
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Pop E, Shek E, Murakami T, Bodor NS. Improved anticonvulsant activity of phenytoin by a redox brain delivery system I: Synthesis and some properties of the dihydropyridine derivatives. J Pharm Sci 1989; 78:609-16. [PMID: 2778665 DOI: 10.1002/jps.2600780802] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Nine chemical delivery systems (CDSs) were synthesized for the efficient transport of phenytoin (DPH) across the blood-brain barrier. The CDSs were based on a dihydropyridine in equilibrium quaternary pyridinium ion redox system which relies on chemistry similar to the NADH in equilibrium NAD interconversion for activity. The chemical carriers, derivatives of trigonelline, 1-alkylcarboxynicotinamide, 3-pyridylacetic acid, and N-methylpicolinic acid, were esterified with 3-(hydroxymethyl)phenytoin. The CDSs proved to be more lipophilic (5-23 times) than DPH. The 1-alkylcarboxydihydronicotinamide CDSs, excluding the sterically hindered one (11e), were quite unstable in rat tissue homogenates and hydrolyzed to release DPH. In human blood, however, they were found to be much more stable (75 times) toward hydrolysis. All other CDSs were oxidized quantitatively to the corresponding pyridinium ion in rat brain homogenates. These compounds were found to possess the required physicochemical characteristics for delivering DPH into rat brain.
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Affiliation(s)
- E Pop
- University of Florida, Center for Drug Design and Delivery, Gainesville
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31
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The Reduction of Nitrogen Heterocycles with Complex Metal Hydrides. ADVANCES IN HETEROCYCLIC CHEMISTRY 1986. [DOI: 10.1016/s0065-2725(08)60762-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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Abstract
Prodrugs are pharmacologically inactive chemical derivatives of a drug molecule that require a transformation within the body in order to release the active drug. They are designed to overcome pharmaceutical and/or pharmacokinetically based problems associated with the parent drug molecule that would otherwise limit the clinical usefulness of the drug. The scientific rationale, based on clinical, pharmaceutical and chemical experience, for the design of various currently used prodrugs is presented in this review. The examples presented are by no means comprehensive, but are representative of the different ways in which the prodrug approach has been used to enhance the clinical efficacy of various drug molecules.
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Gray AP. Design and structure-activity relationships of antidotes to organophosphorus anticholinesterase agents. Drug Metab Rev 1984; 15:557-89. [PMID: 6386410 DOI: 10.3109/03602538409029973] [Citation(s) in RCA: 77] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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34
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Synthetic applications of 2-cyanopiperidines. Model studies in the synthesis of bridged indole alkaloids. Tetrahedron 1984. [DOI: 10.1016/s0040-4020(01)82427-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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35
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Bundgaard H. QUESTIONS AND ANSWERS. J Clin Pharm Ther 1983. [DOI: 10.1111/j.1365-2710.1983.tb01046.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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36
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Kenley RA, Howd RA, Uyeno ET. Effects of PAM, proPAM, and DFP on behavior, thermoregulation, and brain AChE in rats. Pharmacol Biochem Behav 1982; 17:1001-8. [PMID: 7178195 DOI: 10.1016/0091-3057(82)90485-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The effects of pyridine-2 aldoxime methyl iodide (PAM), N-methyl-1,6-dihydro-pyridine-2-carbaldoxime hydrochloride (proPAM), and diisopropyl phosphorofluoridate (DFP) on performance of a conditioned avoidance response (CAR), body temperature, and in vivo acetylcholinesterase (AChE) activity in five brain regions in the rat were examined. Sublethal doses of DFP (1.5 to 2.5 mg/kg, IP) markedly degraded CAR performance. This effect was antagonized by 5 mg/kg, subcutaneously injected (SC) atropine. A 50 mg/kg, SC dose of PAM had no effect on the CAR, but an equal dose of proPAM caused a transient deterioration of performance. Given 10 min or 2 hr after DFP, 50 mg/kg proPAM initially exacerbated the behaviorally toxic effects of DFP. Neither PAM nor proPAM antagonized DFP-induced hypothermia. PAM did not reactivate DFP-inhibited brain AChE, and proPAM reactivated it by only 6 to 12% of control activity.
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Abstract
A dihydropyridine-pyridinium salt type of redox system is used in a general and flexible method for the site-specific or sustained delivery (or both) of drugs to the brain. A biologically active compound linked to a lipoidal dihydropyridine carrier easily penetrates the blood-brain barrier. Oxidation of the carrier part in vivo to the ionic pyridinium salt prevents its elimination from the brain, while elimination from the general circulation is accelerated. Subsequent cleavage of the quaternary carrier-drug species results in sustained delivery of the drug in the brain and facile elimination of the carrier part.
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PROCEEDINGS OF THE BRITISH PHARMACOLOGICAL SOCIETY. Br J Pharmacol 1980. [DOI: 10.1111/j.1476-5381.1980.tb07899.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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41
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Clement JG. Efficacy of pro-PAM (N-methyl-1,6-dihydropyridine-2-carbaldoxime hydrochloride) as a prophylaxis against organophosphate poisoning. Toxicol Appl Pharmacol 1979; 47:305-11. [PMID: 36686 DOI: 10.1016/0041-008x(79)90325-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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42
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Bodor N, Roller RG, Selk SJ. Elimination of a quaternary pyridinium salt delivered as its dihydropyridine derivative from brain of mice. J Pharm Sci 1978; 67:685-7. [PMID: 641811 DOI: 10.1002/jps.2600670531] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
1-Methylpyridine-2-carbaldehyde oxime, a quaternary pyridinium salt, can be delivered efficiently through the blood-brain barrier in its dihydropyridine prodrug form. This redox system was used to study the elimination rate from the brain of a small quaternary salt. It was found that the oxime is eliminated relatively fast from the brain, which supports a hypothesis for the existence of an active transport mechanism for eliminating organic ions from the brain. The possibilities of using the pyridinium salt in equilibrium dihydropyridine redox system for specific delivery of drugs to the brain are discussed.
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