Dextromethorphan, sold under the brand name Robitussin among others, is a cough suppressant used in many cough and cold medicines. In 2022, the US Food and Drug Administration (FDA) approved the combination dextromethorphan/bupropion to serve as a rapid-acting antidepressant in people with major depressive disorder.
It is in the morphinan class of medications with sedative, dissociative, and stimulant properties (at lower doses). Dextromethorphan does not have a significant affinity for the mu-opioid receptor activity typical of morphinan compounds and exerts its therapeutic effects through several other receptors. In its pure form, dextromethorphan occurs as a white powder.
When exceeding approved dosages, dextromethorphan acts as a dissociative hallucinogen. It has multiple mechanisms of action, including actions as a nonselective serotonin reuptake inhibitor and a sigma-1 receptor agonist. Dextromethorphan and its major metabolite, dextrorphan, also block the NMDA receptor at high doses, which produces effects similar to other dissociative anesthetics such as ketamine, nitrous oxide, and phencyclidine.
It was patented in 1949 and approved for medical use in 1953. In 2022, the combination with promethazine was the 260th most commonly prescribed medication in the United States, with more than 1 million prescriptions. In 2022, the combination with brompheniramine and pseudoephedrine was the 265th most commonly prescribed medication in the United States, with more than 1 million prescriptions.
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InChI=1S/C18H25NO/c1-19-10-9-18-8-4-3-5-15(18)17(19)11-13-6-7-14(20-2)12-16(13)18/h6-7,12,15,17H,3-5,8-11H2,1-2H3/t15-,17+,18+/m1/s1 |
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C=1C=2C[C@H]3[C@@]4([C@](C2C=C(C1)OC)(CCCC4)CCN3C)[H] |
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environmental contaminant
Any minor or unwanted substance introduced into the environment that can have undesired effects.
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NMDA receptor antagonist
Any substance that inhibits the action of N-methyl-D-aspartate (NMDA) receptors. They tend to induce a state known as dissociative anesthesia, marked by catalepsy, amnesia, and analgesia, while side effects can include hallucinations, nightmares, and confusion. Due to their psychotomimetic effects, many NMDA receptor antagonists are used as recreational drugs.
neurotoxin
A poison that interferes with the functions of the nervous system.
xenobiotic
A xenobiotic (Greek, xenos "foreign"; bios "life") is a compound that is foreign to a living organism. Principal xenobiotics include: drugs, carcinogens and various compounds that have been introduced into the environment by artificial means.
metabolite
Any intermediate or product resulting from metabolism. The term 'metabolite' subsumes the classes commonly known as primary and secondary metabolites.
(via alkaloid )
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antitussive
An agent that suppresses cough. Antitussives have a central or a peripheral action on the cough reflex, or a combination of both. Compare with expectorants, which are considered to increase the volume of secretions in the respiratory tract, so facilitating their removal by ciliary action and coughing, and mucolytics, which decrease the viscosity of mucus, facilitating its removal by ciliary action and expectoration.
prodrug
A compound that, on administration, must undergo chemical conversion by metabolic processes before becoming the pharmacologically active drug for which it is a prodrug.
oneirogen
Any substance that produces or enhances dream-like states of consciousness.
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(4aS,10S,10aS)-6-methoxy-11-methyl-1,3,4,9,10,10a-hexahydro-2H-10,4a-(epiminoethano)phenanthrene
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3-methoxy-17-methyl-9α,13α,14α-morphinan
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dextromethorphan
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Martin E, Narjoz C, Decleves X, Labat L, Lambert C, Loriot MA, Ducheix G, Dualé C, Pereira B, Pickering G (2019) Dextromethorphan Analgesia in a Human Experimental Model of Hyperalgesia. Anesthesiology 131, 356-368 [PubMed:31094746] [show Abstract]
BackgroundCentral pain sensitization is often refractory to drug treatment. Dextromethorphan, an N-methyl-D-aspartate receptor antagonist, is antihyperalgesic in preclinical pain models. The hypothesis is that dextromethorphan is also antihyperalgesic in humans.MethodsThis randomized, double-blind, placebo-controlled, crossover study explores the antihyperalgesic effect of single and repeated 30-mg dose of oral dextromethorphan in 20 volunteers, using the freeze-injury pain model. This model leads to development of primary and secondary hyperalgesia, which develops away from the site of injury and is associated with central sensitization and activation of N-methyl-D-aspartate receptor in the spinal cord. The primary outcome was antihyperalgesia calculated with the area under the curve of the percentage change in mechanical pain threshold (electronic von Frey) on the area of secondary hyperalgesia. The secondary outcomes were mechanical pain threshold on the area of primary hyperalgesia and cognitive (reaction time) effect.ResultsSingle 30-mg results are reported. Antihyperalgesia (% · min) is significantly higher on the area of secondary hyperalgesia with dextromethorphan than placebo (median [interquartile range]: 3,029 [746; 6,195] vs. 710 [-3,248; 4,439], P = 0.009, Hedge's g = 0.8, 95% CI [0.1; 1.4]). On primary hyperalgesia area, mechanical pain threshold 2 h after drug intake is significantly higher with dextromethorphan (P = 0.011, Hedge's g = 0.63, 95% CI [0.01; 1.25]). No difference in antinociception is observed after thermal painful stimuli on healthy skin between groups. Reaction time (ms) is shorter with placebo than with dextromethorphan (median [interquartile range]: 21.6 [-37.4; 0.1] vs. -1.2 [-24.3; 15.4], P = 0.015, Hedge's g = 0.75, 95% CI [0.12; 1.39]). Nonserious adverse events occurrence (15%, 3 of 20 volunteers) was similar in both groups.ConclusionsThis study shows that low-dose (30-mg) dextromethorphan is antihyperalgesic in humans on the areas of primary and secondary hyperalgesia and reverses peripheral and central neuronal sensitization. Because dextromethorphan had no intrinsic antinociceptive effect in acute pain on healthy skin, N-methyl-D-aspartate receptor may need to be sensitized by pain for dextromethorphan to be effective. | Zarrindast MR, Ownegh V, Rezayof A, Ownegh F (2014) The involvement of dorsal hippocampus in dextromethorphan-induced state-dependent learning in mice. Pharmacology, biochemistry, and behavior 116, 90-95 [PubMed:24269965] [show Abstract] In an effort to understand the effect of dextromethorphan (DM; 3-methoxy-17-methylmorphinan), a noncompetitive antagonist of the N-methyl-d-aspartate (NMDA) receptors on memory retrieval, male NMRI mice received intraperitoneal (i.p.) or intra-CA1 injection of this drug before or after training and before testing in passive avoidance task. Pre-training i.p. (20mg/kg) or intra-CA1 (0.5 and 1 μg/mouse) administration of DM induced amnesia in a dose-dependent manner. Post-training i.p. (10 and 20mg/kg) or intra-CA administration of DM (0.5 and 1 μg/mouse) however, did not affect the memory retrieval. Moreover, memory retrieval was impaired in animals receiving either i.p. (20mg/kg) or intra-CA1 administration of DM (0.5 and 1 μg/mouse) prior to testing, suggesting the DM-induced amnesia. Interestingly, the amnestic effect of pre-training i.p. (20mg/kg) or intra-CA1 administration of DM (1 μg/mouse) was restored in mice receiving pre-test i.p. (5 and 10mg/kg) or intra-CA1 (0.25 and 0.5 μg/mouse) administration of the drug, indicating DM-induced state-dependent learning. Taken together, it can be concluded that DM administration impairs memory retrieval in a dose- and time-dependent manner. Moreover, DM can induce state-dependent learning. Dorsal hippocampus appears to play an important role upon DM influence of learning and memory processes. | Shin EJ, Lee PH, Kim HJ, Nabeshima T, Kim HC (2008) Neuropsychotoxicity of abused drugs: potential of dextromethorphan and novel neuroprotective analogs of dextromethorphan with improved safety profiles in terms of abuse and neuroprotective effects. Journal of pharmacological sciences 106, 22-27 [PubMed:18198471] [show Abstract] Drug abuse involving dextromethorphan, an antitussive, has been a social problem in various geographic locations since the 1960s. Ironically, high doses of the drug confer neuroprotective activity with central nervous system and behavioral effects. Accumulating evidence suggests that metabolism to phencyclidine-like dextrorphan is not essential for the neuroprotective activity of dextromethorphan. Here, we review the neuroprotective properties of dextromethorphan and its potential for abuse and the potential neuroprotective effects of the drug's analogs and 3-hydroxymorphinan, a metabolite of dextromethorphan. These compounds may provide a novel therapeutic direction for the treatment of neurodegenerative diseases such as convulsive or parkinsonian-like disorders. | Aardema MJ, Robison SH, Gatehouse D, Johnston G (2008) An evaluation of the genotoxicity of the antitussive drug Dextromethorphan. Regulatory toxicology and pharmacology : RTP 50, 285-293 [PubMed:18160193] [show Abstract] Dextromethorphan (DMP) is an effective and widely used antitussive drug. While DMP has over a 50 year safe-marketing history, the only available genotoxicity data was an unpublished, negative Ames assay (Roche). Lack of a complete genotoxicity profile on DMP, specifically covering the chromosomal damage endpoint, prompted a regulatory request for an in vitro chromosome aberration assay. In accordance with EC and CPMP Guidance, we evaluated data for a number of chemicals with a structural relationship to DMP. DMP contains no structural alerts for genotoxicity or carcinogenicity using the Deductive Estimation of Risk from Existing Knowledge (DEREK) software tool, confirming the negative results obtained in the existing Ames assay. This is also consistent with the mostly negative genotoxicity and carcinogenicity data available on structurally related chemicals including morphine, codeine, nalbuphine, buprenorphine, naloxone, hydromorphone, levorphanol, and oxycodone. A state-of-the-science, in vitro chromosome aberration assay was also conducted, which demonstrated a lack of genotoxicity for DMP. The overall weight of evidence for DMP and its structural analogues, supports the conclusion that this class of phenanthrene-based chemicals, and DMP, in particular, are not genotoxic in vitro or in vivo, and do not represent a carcinogenic risk to patients. | Siu A, Drachtman R (2007) Dextromethorphan: a review of N-methyl-d-aspartate receptor antagonist in the management of pain. CNS drug reviews 13, 96-106 [PubMed:17461892] [show Abstract] Dextromethorphan (DM) is a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist, which is widely used as an antitussive agent. DM also prevents neuronal damage and modulates pain sensation via noncompetitive antagonism of excitatory amino acids (EAAs). DM has been found to be useful in the treatment of pain in cancer patients and in the treatment of methotrexate-induced neurotoxicity. Clinical studies with DM in cancer patients are reviewed in this article. | Carliss RD, Radovsky A, Chengelis CP, O'Neill TP, Shuey DL (2007) Oral administration of dextromethorphan does not produce neuronal vacuolation in the rat brain. Neurotoxicology 28, 813-818 [PubMed:17573115] [show Abstract] Dextromethorphan is a widely used antitussive agent, also showing increased recreational abuse. Dextromethorphan and its metabolite dextrorphan are non-competitive antagonists at the N-methyl-d-aspartate (NMDA) receptor ion channel. Single doses of some NMDA receptor antagonists produce neuropathologic changes in neurons of the retrosplenial/posterior cingulate cortices (RS/PC), characterized by vacuolation or neurodegeneration. To determine whether dextromethorphan produces these characteristic lesions, dextromethorphan was administered orally either as a single dose of 120mg/kg to female rats, or daily for 30 days at doses of 5-400 mg/(kg day) to male rats and 5-120mg/(kg day) to female rats. Brains were examined microscopically for evidence of neuronal vacuolation (4-6h postdose) and neurodegeneration ( approximately 24 or 48h postdose). Administration of dextromethorphan at 120mg/(kg day) in females, and at > or =150mg/(kg day) in males produced marked behavioral changes, indicative of neurologic effects. Mortality occurred at the highest doses administered. There were no detectable neuropathologic changes following single or repeated oral administration of dextromethorphan at any dose. Administration of MK-801 (9mg/kg) produced both cytoplasmic vacuolation and neuronal degeneration in neurons of the RS/PC cortex. Thus characteristic neuropathologic changes found with more potent NMDA receptor antagonists do not occur following single or repeated oral administration of dextromethorphan. | Thisted RA, Klaff L, Schwartz SL, Wymer JP, Culligan NW, Gerard G, Pope LE, Berg JE (2006) Dextromethorphan and quinidine in adult patients with uncontrolled painful diabetic peripheral neuropathy: a 29-day, multicenter, open-label, dose-escalation study. Clinical therapeutics 28, 1607-1618 [PubMed:17157116] [show Abstract]
BackgroundPain associated with diabetic peripheral neuropathy (DPN) has a substantial negative impact on patients' quality of life.ObjectivesThe primary objective of this study was to evaluate the tolerability of capsules containing dextromethorphan (DM) and quinidine (Q) in patients with painful DPN. A secondary objective was to perform a preliminary assessment of the efficacy of DM/Q in this patient population.MethodsThis was a multicenter, open-label, dose-escalation study. Eligible patients were aged between 18 and 80 years, had a confirmed diagnosis of diabetes with acceptable glycemic control, had been receiving established diabetic therapy for at least 3 months, and had a clinical diagnosis of distal symmetric sensory neuropathy with daily DPN-associated pain for the previous 3 months. On study entry, patient-rated diabetic pain had to be moderate or greater. Patients who met the inclusion criteria underwent a 2-week washout period during which all analgesics were discontinued, followed by 29 days of treatment with capsules containing DM 30 mg and Q 30 mg (DM30/Q30), beginning with 1 capsule/d and escalating at approximately 1-week intervals, as tolerated, to a maximum dose of 4 capsules/d (DM120/Q120). Tolerability was assessed based on adverse events and changes in clinical and laboratory parameters and nerve conduction velocity. Preliminary efficacy assessments included changes from baseline in scores on the pain intensity rating scale (PIRS), pain relief rating scale (PRRS), peripheral neuropathy quality-of-life instrument, and patients' diary assessments of sleep, present pain intensity, pain, and activity.ResultsThe study included 36 men and women (mean age, 58 years; mean body mass index, 32.8 kg/m(2)). Of the 33 subjects who completed the study, 23 (69.7%) did so at the highest permitted dose (DM120/Q120). The most commonly reported adverse events (occurring in > or =5% of subjects) were nausea (27.8%), dizziness (25.0%), and headache (25.0%). Three patients experienced 5 serious adverse events, only 1 of which was considered possibly related to study drug. The most commonly occurring laboratory abnormalities (involving glycosylated hemoglobin, serum glucose, triglycerides, and cholesterol) were considered typical of a population with diabetes. Improvements from baseline in scores on the PIRS, PRRS, and other exploratory efficacy measures were noted (P < 0.001).ConclusionsThe results of this open-label study indicated that the combination of DMIQ (dose range, DM30/Q30-DM120/Q120) was well tolerated in patients with pain associated with DPN. Based on the preliminary efficacy results, a randomized, controlled, double-blind trial is warranted to assess the tolerability and efficacy of this combination in patients with DPN. | Brooks BR, Thisted RA, Appel SH, Bradley WG, Olney RK, Berg JE, Pope LE, Smith RA, AVP-923 ALS Study Group (2004) Treatment of pseudobulbar affect in ALS with dextromethorphan/quinidine: a randomized trial. Neurology 63, 1364-1370 [PubMed:15505150] [show Abstract]
BackgroundPatients with ALS commonly exhibit pseudobulbar affect.MethodsThe authors conducted a multicenter, randomized, double-blind, controlled, parallel, three-arm study to test a defined combination of dextromethorphan hydrobromide (DM) and quinidine sulfate (Q) (AVP-923) for the treatment of pseudobulbar affect in ALS. Q inhibits the rapid first-pass metabolism of DM. The effects of AVP-923 (30 mg of DM plus 30 mg of Q) given twice daily for 28 days were compared with those of its components. Patients were evaluated on days 1, 15, and 29. The primary efficacy variable was the change from baseline in the Center for Neurologic Study Lability Scale (CNS-LS) score. Secondary efficacy variables were laughing/crying episode rates and changes in Visual Analog Scales for Quality of Life (QOL) and Relationships (QOR). Efficacy was evaluated in intention-to-treat subjects who were not poor metabolizers of DM (n = 65 for AVP-923, n = 30 for DM, and n = 34 for Q). Safety was assessed in all randomized subjects (n = 140).ResultsAVP-923 patients experienced 3.3-point greater improvements in CNS-LS than DM patients (p = 0.001) and 3.7-point greater improvements than Q patients (p < 0.001). AVP-923 patients exhibited lower overall episode rates, improved QOL scores, and improved QOR scores (p < 0.01 for all endpoints). Adverse effects were mostly mild or moderate; treatment-related discontinuation was 24% for AVP-923, 6% for DM, and 8% for Q.ConclusionsAVP-923 palliates pseudobulbar affect in ALS. Overall benefits of treatment are reflected in fewer episodes of crying and laughing and improvements in overall quality of life and quality of relationships. | Zhu H, Jenab S, Jones KL, Inturrisi CE (2003) The clinically available NMDA receptor antagonist dextromethorphan attenuates acute morphine withdrawal in the neonatal rat. Brain research. Developmental brain research 142, 209-213 [PubMed:12711372] [show Abstract] We investigated the ability of dextromethorphan, a clinically available NMDA receptor antagonist, to attenuate the behaviors and the expression of c-fos mRNA associated with acute morphine withdrawal in the 7-day-old rat. The intensity of the acute morphine withdrawal behaviors and the elevation in c-fos mRNA expression in the brain induced by acute morphine withdrawal were reduced by dextromethorphan. Thus, dextromethorphan can attenuate acute morphine withdrawal in the developing organism. | Hernandez SC, Bertolino M, Xiao Y, Pringle KE, Caruso FS, Kellar KJ (2000) Dextromethorphan and its metabolite dextrorphan block alpha3beta4 neuronal nicotinic receptors. The Journal of pharmacology and experimental therapeutics 293, 962-967 [PubMed:10869398] [show Abstract] Dextromethorphan (DM), a structural analog of morphine and codeine, has been widely used as a cough suppressant for more than 40 years. DM is not itself a potent analgesic, but it has been reported to enhance analgesia produced by morphine and nonsteroidal anti-inflammatory drugs. Although DM is considered to be nonaddictive, it has been reported to reduce morphine tolerance in rats and to be useful in helping addicted subjects to withdraw from heroin. Here we studied the effects of DM on neuronal nicotinic receptors stably expressed in human embryonic kidney cells. Studies were carried out to examine the effects of DM on nicotine-stimulated whole cell currents and nicotine-stimulated (86)Rb(+) efflux. We found that both DM and its metabolite dextrorphan block nicotinic receptor function in a noncompetitive but reversible manner, suggesting that both drugs block the receptor channel. Consistent with blockade of the receptor channel, neither drug competed for the nicotinic agonist binding sites labeled by [(3)H]epibatidine. Although DM is approximately 9-fold less potent than the widely used noncompetitive nicotinic antagonist mecamylamine in blocking nicotinic receptor function, the block by DM appears to reverse more slowly than that by mecamylamine. These data indicate that DM is a useful antagonist for studying nicotinic receptor function and suggest that it might prove to be a clinically useful neuronal nicotinic receptor antagonist, possibly helpful as an aid for helping people addicted to nicotine to refrain from smoking, as well as in other conditions where blockade of neuronal nicotinic receptors would be helpful. | Tang YW, Rys PN, Rutledge BJ, Mitchell PS, Smith TF, Persing DH (1998) Comparative evaluation of colorimetric microtiter plate systems for detection of herpes simplex virus in cerebrospinal fluid. Journal of clinical microbiology 36, 2714-2717 [PubMed:9705419] [show Abstract] In the past few years, application of the PCR to the detection of herpes simplex virus (HSV) DNA in the cerebrospinal fluid (CSF) from patients with encephalitis and meningitis has become standard laboratory practice. However, from an operational perspective, the true diagnostic value of PCR in this setting is yet to be realized because most laboratories subject the amplification products to lengthy probe hybridization procedures by Southern blotting. As alternatives to Southern blotting, we evaluated colorimetric microtiter plate (MTP) systems from ViroMed Laboratories, Inc. (PrimeCapture), CPG, Inc. (Quanti-PATH), and Incstar Corp. (GEN-ETI-K), in addition to a system developed at the Mayo Clinic with the PCR ELISA system (Boehringer Mannheim Corp.). We tested PCR products from 86 clinical CSF specimens submitted to our Molecular Microbiology Laboratory. The CSF specimens used had to have sufficient volume for comparative analysis. By conventional Southern blotting methods, 54 were positive and 32 were negative for HSV DNA. Compared with Southern blotting, the sensitivity and specificity were 63.0 and 100.0%, respectively, for the PrimeCapture system, 98. 2 and 96.9%, respectively, for the Quanti-PATH system, 98.2 and 100. 0%, respectively, for the GEN-ETI-K system, and 100.0 and 96.9%, respectively, for the Mayo system. All four MTP systems had turnaround times 12 to 24 h less than that for Southern blotting. There were no significant differences in costs or technologist time between the Mayo system and Southern blotting. Other features of the Mayo system include type-specific genotypic identification of HSV and the potential for determination of drug resistance by DNA sequencing. Overall, we found that colorimetric MTP systems were likely to improve test turnaround times and patient care at no additional cost. | Hargreaves RJ, Hill RG, Iversen LL (1994) Neuroprotective NMDA antagonists: the controversy over their potential for adverse effects on cortical neuronal morphology. Acta neurochirurgica. Supplementum 60, 15-19 [PubMed:7976530] [show Abstract] It has been reported that several uncompetitive NMDA receptor ion channel blocking agents (phencyclidine, ketamine, dizocilpine, dextrorphan) cause transient reversible vacuolation in neurons in the posterior cingulate cortex of rats. Similar effects have also been observed with competitive glutamate antagonists such as CPP, CGS 19755 and CGP 37849. This transient morphological change has been noted to be coincident anatomically with brain regions showing hypermetabolism after administration of uncompetitive NMDA receptor ion channel blockers and competitive glutamate antagonists. These results therefore indicate that the functional consequences of NMDA receptor blockade with competitive glutamate and uncompetitive channel antagonists are ultimately the same. These changes do not appear to be a prelude to irreversible damage except after relatively high doses of the receptor ion channel antagonists but they have given rise to concern over the safety in use of NMDA antagonists as neuroprotective agents. In contrast, vacuolation has not yet been demonstrated with agents acting at the glycine (L-687,414) or polyamine (eliprodil) modulatory sites of the NMDA receptor complex suggesting that agents acting at these sites may have a greater potential therapeutic window. | Schmitt B, Netzer R, Fanconi S, Baumann P, Boltshauser E (1994) Drug refractory epilepsy in brain damage: effect of dextromethorphan on EEG in four patients. Journal of neurology, neurosurgery, and psychiatry 57, 333-339 [PubMed:8158182] [show Abstract] High doses of dextromethorphan (20-42 mg/kg/day) were given to four critically ill children with seizures and frequent epileptiform abnormalities in the EEG that were refractory to antiepileptic drugs. Their acute diseases (hypoxia, head trauma and hypoxia, neurodegenerative disease, hypoglycaemia) were thought to be due in part to N-methyl-D-aspartate (NMDA) receptor mediated processes. Treatment with dextromethorphan, an NMDA receptor antagonist, was started between 48 hours and 14 days after the critical incident. In three patients the EEG improved considerably within 48 hours and seizures ceased within 72 hours. In the patient with neurodegenerative disease the effect on the EEG was impressive, but the seizures were not controlled. Despite the improvement of the EEG the clinical outcome was poor in all children: three died in the critical period or due to the progressing disease; the patient with hypoglycaemia survived with severe neurological sequelae. Plasma concentrations of dextromethorphan varied between 74-1730 ng/ml and its metabolite dextrorphan varied between 349-3790 ng/ml. In one patient corresponding concentrations in CSF were lower than those in plasma. The suppression of epileptic discharges by the doses of dextromethorphan given suggests that such doses are sufficient to block NMDA receptors. | Olney JW, Labruyere J, Price MT (1989) Pathological changes induced in cerebrocortical neurons by phencyclidine and related drugs. Science (New York, N.Y.) 244, 1360-1362 [PubMed:2660263] [show Abstract] Phencyclidine (PCP), a dissociative anesthetic and widely abused psychotomimetic drug, and MK-801, a potent PCP receptor ligand, have neuroprotective properties stemming from their ability to antagonize the excitotoxic actions of endogenous excitatory amino acids such as glutamate and aspartate. There is growing interest in the potential application of these compounds in the treatment of neurological disorders. However, there is an apparent neurotoxic effect of PCP and related agents (MK-801, tiletamine, and ketamine), which has heretofore been overlooked: these drugs induce acute pathomorphological changes in specific populations of brain neurons when administered subcutaneously to adult rats in relatively low doses. These findings raise new questions regarding the safety of these agents in the clinical management of neurodegenerative diseases and reinforce concerns about the potential risks associated with illicit use of PCP. |
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