dextromethorphan and Ataxia

Compounds with anti-glutamatergic properties currently in clinical use for various indications (eg Alzheimer's disease, epilepsy, psychosis, mood disorders) have potential utility as novel treatments for alcoholism. Enhanced sensitivity to certain acute intoxicating effects (ataxia, sedative) of alcohol may be one mechanism by which anti-glutamatergic drugs modulate alcohol use. We examined the effects of six compounds (memantine, dextromethorphan, haloperidol, lamotrigine, oxcarbazepine, and topiramate) on sensitivity to acute intoxicating effects of ethanol (ataxia, hypothermia, sedation/hypnosis) in C57BL/6J mice. Analysis of topiramate was extended to determine the influence of genetic background (by comparison of the 129S1, BALB/cJ, C57BL/6J, DBA/2J inbred strains) and prior stress history (by chronic exposure of C57BL/6J to swim stress) on topiramate's effects on ethanol-induced sedation/hypnosis. Results showed that one N-methyl-D-aspartate receptor (NMDAR) antagonist, memantine, but not another, dextromethorphan, potentiated the ataxic but not hypothermic or sedative/hypnotic effects of ethanol. Haloperidol increased ethanol-induced ataxia and sedation/hypnosis to a similar extent as the prototypical NMDAR antagonist MK-801. Of the anticonvulsants tested, lamotrigine accentuated ethanol-induced sedation/hypnosis, whereas oxcarbazepine was without effect. Topiramate was without effect per se under baseline conditions in C57BL/6J, but had a synergistic effect with MK-801 on ethanol-induced sedation/hypnosis. Comparing inbred strains, topiramate was found to significantly potentiate ethanol's sedative/hypnotic effects in BALB/cJ, but not 129S1, C57BL/6J, or DBA/2J strains. Topiramate also increased ethanol-induced sedation/hypnosis in C57BL/6J after exposure to chronic stress exposure. Current data demonstrate that with the exception of MK-801 and haloperidol, the compounds tested had either no significant or assay-selective effects on sensitivity to acute ethanol under baseline conditions in C57BL/6J. However, significant effects of topiramate were revealed as a function of co-treatment with an NMDAR blocker, genetic background, or prior stress history. These findings raise the possibility that topiramate and possibly other anti-glutamatergic drugs could promote the acute intoxicating effects of ethanol in specific subpopulations defined by genetics or life history.

Topics: Alcoholic Intoxication; Animals; Ataxia; Carbamazepine; Central Nervous System Depressants; Conscious Sedation; Dextromethorphan; Ethanol; Excitatory Amino Acid Agents; Fructose; Haloperidol; Hypothermia; Lamotrigine; Male; Memantine; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred DBA; Oxcarbazepine; Species Specificity; Stress, Psychological; Topiramate; Triazines

We investigated the effects of the centrally acting antitussives dextromethorphan and cloperastine on urinary bladder dysfunction 24 h after cerebral infarction in rats using the cystometry technique. First, cystometrography was performed in conscious male Sprague-Dawley rats. Cerebral infarction was then induced by occlusion of the left middle cerebral artery. Twenty-four hours after cerebral infarction, the effect of each drug on micturition disorder was estimated for 5 parameters: bladder capacity, maximum voiding pressure, micturition latency, flow rate, and urethral resistance. Cerebral infarction markedly reduced bladder capacity, micturition latency, and flow rate and increased urethral resistance. After cerebral infarction, intravenous dosing of saline had no effect on these parameters. Dextromethorphan (20 mg/kg) and cloperastine (2.5 and 5.0 mg/kg) at antitussive effective doses significantly increased bladder capacity and micturition latency. Unlike dextromethorphan, cloperastine ameliorated decreases in flow rate and increases in urethral resistance caused by cerebral infarction. These results suggest that cloperastine may have therapeutic value for the treatment of disorders of the micturition reflex associated with cerebral infarction, and that the drug may become a base compound from which to develop more active drugs for such disorders.

Topics: Animals; Antitussive Agents; Ataxia; Dextromethorphan; Diagnostic Techniques, Urological; Infarction, Middle Cerebral Artery; Male; Piperidines; Rats; Rats, Sprague-Dawley; Urinary Bladder; Urinary Bladder, Overactive; Urination

Excitatory amino acids (EAA) and particularly glutamate toxicity have been implicated in the pathogenesis of neuronal injury occurring in bacterial meningitis by activating the N-methyl-d aspartate (NMDA) receptor complex. Here, we evaluated the effect of adjuvant treatment with the antitussive drug dextromethorphan (DM), a non-competitive NMDA receptor antagonist with neuroprotective potential, in an infant rat model of pneumococcal meningitis. The experiments were carried out in postnatal day 6 (P6) and 11 (P11) animals. Pharmacokinetics of DM and its major metabolite dextrorphan (DO) were performed for dose finding. In our study, DM did not alter clinical parameters (clinical score, motor activity, incidence of seizures, spontaneous mortality) and cortical neuronal injury but increased the occurrence of ataxia (P<0.0001). When DM treatment was started at the time of infection (DM i.p. 15 mg/kg at 0, 4, 8 and 16 hours (h) post infection) in P11 animals, an aggravation of apoptotic neuronal death in the hippocampal dentate gyrus was found (P<0.05). When treatment was initiated during acute pneumococcal meningitis (DM i.p. 15 mg/kg at 12 and 15 h and 7.5 mg/kg at 18 and 21 h after infection), DM had no effect on the extent of brain injury but reduced the occurrence of seizures (P<0.03). We conclude that in this infant rat model of pneumococcal meningitis interference of the EEA and NMDA pathway using DM causes ataxia, attenuates epileptic seizures and increases hippocampal apoptosis, but is not effective in protecting the brain from injury.

Topics: Animals; Apoptosis; Ataxia; Brain; Dextromethorphan; Dose-Response Relationship, Drug; Meningitis, Pneumococcal; Neurons; Rats; Receptors, N-Methyl-D-Aspartate; Seizures

Dextromethorphan (DM), a widely used and well-tolerated centrally acting antitussive, has been tested in several clinical trials for its antiepileptic and neuroprotective properties. However, the use of DM in these new clinical indications requires higher doses than antitussive doses, which may therefore induce phencyclidine (PCP)-like side-effects (memory and psychotomimetic disturbances) through its metabolic conversion to the active metabolite dextrorphan (DX), a more potent PCP-like non-competitive antagonist at the N-methyl-D-aspartate (NMDA) receptor than DM. Thus, we compared the behavioural effects in rats of intraperitoneal administration of DM and DX on motor activity in an open field and on learning and memory in the Morris water maze. DM (20, 30, 40 mg/kg) produced a dose-dependent decrease in both locomotion and stereotyped behaviour with a slight ataxia for the highest dose. DX (20, 30, 40 mg/kg) induced a dose-dependent increase in locomotion and stereotypies (swaying, turning) with moderate ataxia. Assessments of learning and memory were performed with lower doses of DM (10, 20, 30 mg/kg) and DX (5, 10, 15 mg/kg) because of motivational deficits (40 mg/kg of DM, 20-40 mg/kg of DX) and motor disorders (30, 40 mg/kg of DX) in the cue learning procedure. DX (10, 15 mg/kg) impaired spatial learning with a long-lasting effect for the highest dose whereas 5 mg/kg of DX and DM (10-30 mg/kg) did not. Only 15 mg/kg of DX appeared to slightly impair working memory. DM (10-30 mg/kg) and DX (5-15 mg/kg) did not impair reference memory. Thus, the two antitussives DM and DX induced different behavioural effects suggesting sedative effects for DM and PCP-like effects for DX. However, PCP-like side-effects with DM remain possible through its metabolic conversion to DX, with very high doses and/or in extensive metabolizers and/or in aged subjects prone to cognitive dysfunction. Therefore, the identification of DM metabolism phenotype, an adapted prescription and a pharmacological modulation of the DM metabolism may avoid adverse effects.

Topics: Animals; Antitussive Agents; Ataxia; Cues; Dextromethorphan; Dextrorphan; Male; Maze Learning; Memory; Motor Activity; Rats; Rats, Wistar; Stereotyped Behavior

Accidental ingestions of cough and cold preparations containing dextromethorphan (DM) are common in the toddler age group and rarely have serious consequences. Even large intentional overdoses by adults seldom lead to serious morbidity. There have been no previous reports of an extrapyramidal reaction due to a DM ingestion.. We report a 30-month-old girl who ingested approximately 38 mg/kg dextromethorphan. She presented with opisthotonus, ataxia, and bidirectional nystagmus. There was no change in her status with the administration of naloxone. The child was given diphenhydramine with clearing of her opisthotonus but persistence of her ataxia and nystagmus.. A moderate ingestion of dextromethorphan in a toddler resulted in extrapyramidal symptoms with opisthotonus that responded to diphenhydramine. Dextromethorphan is known to have complex CNS effects and, in sufficient doses, may have dopamine receptor blocking activity resulting in this dystonic reaction.

Topics: Antidotes; Antitussive Agents; Ataxia; Child, Preschool; Dextromethorphan; Diphenhydramine; Dystonia; Female; Humans; Nystagmus, Pathologic; Poisoning

The case of a 23-year-old man who was acutely intoxicated on dextromethorphan and who was chronically addicted to the drug is described. He consumed the highest daily dose for the longest duration yet reported in the world's English-language medical literature. Toxicity, abuse potential, and therapy of dextromethorphan intoxication are discussed.

Topics: Adult; Ataxia; Dextromethorphan; Humans; Male; Neurologic Examination; Substance-Related Disorders

Although N-methyl-D-Aspartate (NMDA) antagonists protect against focal cerebral ischaemia, there is concern that the high doses necessary for neuroprotection may cause unacceptable adverse effects. We studied the dose response characteristics of the clinically available NMDA antagonist dextromethorphan in a rabbit model of transient focal ischaemia. Thirty-three anaesthetized rabbits underwent occlusion of the left internal carotid and anterior cerebral arteries for 1 h followed by 4.5 h of reperfusion. One hour after the onset of ischaemia, they were treated with an i.v. infusion of varying doses of dextromethorphan or normal saline. Seventeen additional unanaesthetized, nonischaemic rabbits received similar infusions of dextromethorphan to correlate brain with blood levels and to evaluate adverse effects. Rabbits with plasma dextromethorphan levels 500-1500 ng ml-1 had a 64% reduction in ischaemic neuronal damage (p < 0.05); those with levels > 1500 ng ml-1 showed 92% attenuation of neuronal damage and 65% decrease in ischaemic oedema (p < 0.01). Drug levels suggest that dextromethorphan's neuroprotection is not mediated by its active metabolite dextrorphan. Unanaesthetized rabbits with plasma levels > 2500 ng ml-1 demonstrated severe gait ataxia. These results demonstrate that systemic treatment with dextromethorphan after 1 h of focal ischaemia can significantly protect against cerebral damage if adequate plasma and brain levels are achieved. Dextromethorphan was concentrated 7-30 x in brain compared with plasma, and brain levels were highly correlated with plasma levels (r = 0.89). Neuroprotective doses of dextromethorphan were tolerated with only transient side effects.

Topics: Animals; Ataxia; Brain Chemistry; Brain Edema; Brain Ischemia; Dextromethorphan; Drug Evaluation, Preclinical; Magnetic Resonance Imaging; Male; Rabbits; Receptors, N-Methyl-D-Aspartate; Respiration Disorders

The behavioral effects of dextromethorphan (DM), dextrorphan (DO) and phencyclidine (PCP) were compared in rats. DO (15-120 mg/kg) was similar to PCP (1.25-20 mg/kg) in inducing dose-dependent locomotor hyperactivity, stereotypy and ataxia. DM (15-120 mg/kg) induced moderate hyperactivity only at the higher doses about 45 min after treatment. DM and DO modified the locomotor facilitation induced by 10 mg/kg PCP in opposite directions. Pretreatment with DO facilitated, whereas DM dose-dependently inhibited PCP-elicited hyperactivity. Although the metabolism of DM in rats is unknown, the recently reported abuse of DM in humans may occur by its conversion to DO in the organism, i.e., to a metabolite which produces PCP-like effects.

Topics: Animals; Ataxia; Behavior, Animal; Dextromethorphan; Dextrorphan; Dose-Response Relationship, Drug; Male; Motor Activity; Phencyclidine; Rats; Rats, Inbred Strains; Stereotyped Behavior