Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A recently discovered and structurally distinct class of antiepileptic drugs is the (arylalkyl)imidazoles. Two independently discovered representatives of this class, denzimol (alpha-[4-(2-phenylethyl)phenyl]-1H-imidazole-1-ethanol) and nafimidone (2-(1H-imidazol-1-yl)-1-(2-naphthalenyl)ethanone), are undergoing clinical evaluation. Our structure-activity relationship (SAR) studies revealed that in addition to the naphthalenyl and phenethylphenyl aryl moieties of nafimidone and denzimol, respectively, fluorenyl, benzo[b]thienyl, and benzofuranyl aryl groups provided several highly active (arylalkyl)imidazole anticonvulsants. These structurally diverse aryl moieties, and comparable anticonvulsant activities, lend credence to the hypothesis that the pharmacophore of this class of anticonvulsants is the alkylimidazole portion of the molecule, with the lipophilic aryl portion enabling penetration of the blood-brain barrier. We focused our SAR studies on the (fluorenylalkyl)imidazole series. A representative compound from this series is 1-(9H-fluoren-2-yl)-2-(1H-imidazol-1-yl)ethanone. This agent was twice as potent as nafimidone in inhibiting maximal electroshock seizures in mice (po ED50's = 25 and 56 mg/kg, respectively) and considerably less toxic in the rat (po LD50's = 4550 and 504 mg/kg, respectively). The tertiary alcohol alpha-(9H-fluoren-2-yl)-alpha-methyl-1H-imidazole-1-ethanol was as potent as denzimol in mice (po ED50's = 10 and 12 mg/kg, respectively). This series of imidazole anticonvulsants was highly selective; while many compounds displayed potent antielectroshock activity, little or not activity was observed against pentylenetetrazole-induced clonic seizures or in the horizontal screen test for ataxia. All active compounds that we tested in this series, as well as denzimol and nafimidone, potentiated hexobarbital-induced sleeping time in mice, probably by imidazole-mediated inhibition of cytochrome P-450. The SAR's for the anticonvulsant activity and the sleeping time potentiation were similar. The propensity of these (arylalkyl)imidazole anticonvulsants to interact strongly with cytochrome P-450 and thereby impair the metabolism of other antiepileptic drugs may severely limit their clinical utility as anticonvulsants.
 ...
PMID:Structure-activity relationships of (arylalkyl)imidazole anticonvulsants: comparison of the (fluorenylalkyl)imidazoles with nafimidone and denzimol. 374 10

The authors report a case of erythromycin-induced carbamazepine toxicity in a 6-year-old child following use of erythromycin ethylsuccinate (50 mg/kg/day). Within 5 days of erythromycin use, vomiting, weakness, lethargy, ataxia, nystagmus, and cogwheeling movements developed. A serum carbamazepine concentration had increased from 11.9 mg/L (measured 1 week prior to antibiotic use) to 25.8 mg/L. Following erythromycin withdrawal, serum concentrations returned toward baseline, and symptoms resolved. Erythromycin has known effects on hepatic enzyme function, with altered cytochrome P-450 function. The dramatic reduction in carbamazepine clearance observed in this patient is similar to that reported when erythromycin is used concurrently with other drugs. A brief review of potentially significant erythromycin drug interactions is presented.
 ...
PMID:Erythromycin-induced drug interactions. An illustrative case and review of the literature. 381 8

The sensitivity of the mouse to organophosphorus-induced delayed neurotoxicity (OPIDN) has been investigated. One group of five mice received two single 1000-mg/kg po doses of tri-o-cresyl phosphate (TOCP) at a 21-day interval (on Days 1 and 21 of the study); a second group of five mice was given 225 mg/kg of TOCP daily for 270 days. A third group of five animals served as an untreated control. All animals were killed 270 days after the start of the experiment. Daily po dosing of 225 mg/kg TOCP caused a decrease in body weight gain, muscle wasting, weakness, and ataxia which progressed to severe hindlimb paralysis at termination. On the other hand, po administration of two single 1000-mg/kg doses of TOCP at a 21-day interval produced no observable adverse effects. Brain acetylcholinesterase (AChE) and neurotoxic esterase (NTE) activity were 35 and 10% of the control, respectively, in daily dosed animals while AChE and NTE in mice receiving two single 1000-mg/kg doses of TOCP were not significantly altered from the control group. Plasma butyrylcholinesterase activity was 12% of the control group in daily dosed animals. Hepatic microsomal enzyme activities of aniline hydroxylase and p-chloro-N-methylaniline demethylase and NADPH-cytochrome P-450 content in daily dosed animals were increased (141 to 161% of the control group) when compared to controls and mice receiving two single 1000-mg/kg doses of TOCP; the latter being not significantly different from each other. Degeneration of the axon and myelin of the spinal cord and sciatic fascicle were observed and were consistent with OPIDN. This study demonstrates that chronic dosing of TOCP produces OPIDN and induces hepatic microsomal enzyme activity in mice. It is concluded that while the mouse is susceptible to OPIDN, it is a less sensitive and a less appropriate test animal for studying this effect when compared to the adult hen.
 ...
PMID:Characterization of delayed neurotoxicity in the mouse following chronic oral administration of tri-o-cresyl phosphate. 404 9

The effect of methyl isobutyl ketone (MiBK) on n-hexane-induced neurotoxicity was investigated via inhalation in seven groups of five hens each for 90 days followed by a 30-day observation period. One group was exposed to vapors containing 1000 ppm n-hexane and another group to vapors having 1000 ppm MiBK. Four groups were exposed simultaneously to 1000 ppm of n-hexane and 100, 250, 500, or 1000 ppm MiBK. Another group was exposed similarly to ambient air in an exposure chamber and used as a control. Hens continuously exposed to 1000 ppm MiBK developed leg weakness with subsequent recovery, while inhalation of the same concentration of n-hexane produced mild ataxia. Hens exposed to mixtures of n-hexane and MiBK developed clinical signs of neurotoxicity, the severity of which depended on the MiBK concentration. Thus, all hens exposed to 1000 ppm n-hexane in combination with 250, 500, or 1000 ppm MiBK progressed to paralysis. Hens continuously exposed to 1000/100 n-hexane/MiBK showed severe ataxia which did not change during the observation period. The neurologic dysfunction in hens exposed simultaneously to n-hexane and MiBK was accompanied by large swollen axons and degeneration of the axon and myelin of the spinal cord and peripheral nerves. The results indicate that the nonneurotoxic chemical MiBK synergized the neurotoxic action of the weak neurotoxicant n-hexane since the coneurotoxicity coefficient for joint exposure was more than two times the additive effect of each treatment alone. In another experiment, to investigate the mechanism of MiBK synergism of n-hexane neurotoxicity, continuous inhalation for 50 days of 1000 ppm n-hexane had no effect on hen hepatic microsomal enzymes, whereas inhalation of 1000 ppm MiBK for 50 days or a mixture of 1000 ppm of each of n-hexane and MiBK for 30 days significantly induced aniline hydroxylase activity and cytochrome P-450 contents in hen liver microsomes. Liver microsomal proteins from these hens and from hens treated with beta-naphthoflavone (beta-NF) and phenobarbital (PB) were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. While beta-NF increased the 55-kDa band (1408%), PB, MiBK, and MiBK/n-hexane increased the protein band (49 kDa) (258, 335, and 253%, respectively), indicating that MiBK induces chicken hepatic cytochrome P-450. The results suggest that the synergistic action of MiBK on n-hexane neurotoxicity may be related to its ability to induce liver microsomal cytochrome P-450, resulting in increased metabolic activation of n-hexane to more potent neurotoxic metabolites.
 ...
PMID:The synergism of n-hexane-induced neurotoxicity by methyl isobutyl ketone following subchronic (90 days) inhalation in hens: induction of hepatic microsomal cytochrome P-450. 404 11

We report a case of serotonin syndrome that occurred in a patient with chronic heart failure associated with a panic disorder. The 39-year-old Japanese man had been treated with paroxetine at 20 mg/d for 1 1/2 years. He presented with rhabdomyolysis, renal failure, fulminant liver failure, cardiac conduction disturbance, and disseminated intravascular coagulation, as well as conventional symptoms of serotonin syndrome including alterations in cognition (disorientation, confusion) and behavior (restlessness), autonomic nervous system dysfunction (fever, shivering), and abnormal neuromuscular activity (ataxia, hyperreflexia, myoclonus). All medications prescribed before hospital admission were discontinued. After 24 hours of continuous venovenous hemofiltration, diuresis resumed and renal and liver function improved rapidly. Disorientation, restlessness, hyperreflexia, and myoclonus abated slowly over the next 72 hours. The patient's anxiety subsided more slowly, and he recovered completely 1 week later. The plasma concentration of paroxetine was elevated far above the upper limit of the therapeutic range. The patient had cytochrome P-450 (CYP) 2D6*1/*5, a heterozygosity of an inactivated allele of CYP2D6, which metabolizes paroxetine. The patient was determined to be an intermediate metabolizer who was potentially vulnerable to paroxetine, a major inhibitor of CYP2D6. Heart failure is often accompanied by psychiatric disorders. A wide range of drugs commonly prescribed for these conditions, including beta-blockers, antiarrhythmics, and antidepressants, are metabolized by CYP2D6. Genetic screening for CYP2D6 in patients with these conditions may prevent life-threatening drug intoxication.
 ...
PMID:Life-threatening serotonin syndrome in a patient with chronic heart failure and CYP2D6*1/*5. 1554 25