Acute psychotic symptoms induced by topiramate.
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The incidence of psychosis during clinical trials of topiramate was 0.8%, not significantly different from the rate for placebo or reported rates of psychosis in patients with refractory epilepsy. We observed psychotic symptoms in five patients soon after initiation of topiramate therapy. We performed a retrospective chart review of the first 80 patients who began on topiramate after approval for clinical use, between January and April 1997. Symptoms suggestive of psychosis, including hallucinations and delusions, were sought for analysis. Cognitive effects such as psychomotor slowing, confusion, and somnolence were not included. Five patients developed definite psychotic symptoms 2 to 46 days after beginning topiramate. Dosages at symptom onset were 50-400 mg/day. Symptoms included paranoid delusions in four patients and auditory hallucinations in three. Symptoms of psychosis and other psychiatric symptoms resolved quickly with discontinuation of topiramate in three patients, dose reduction from 300 to 200 mg/day in one and with inpatient treatment and neuroleptics in another. One patient had a history of auditory hallucinations, one of aggressive and suicidal thoughts, but three had no significant psychiatric history. Physicians should be aware of the possibility of psychotic symptoms, even in patients without a previous psychiatric history, when prescribing topiramate. Symptoms resolve quickly with discontinuation. (+info)
Carbamazepine, hepatotoxicity, organic solvents, and paints.
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Hepatotoxicity secondary to carbamazepine is a serious condition which can be fatal. However, other concomitant medications or environmental factors may be the offending agents. In this case report, hepatotoxicity secondary to organic solvents and paints is described. (+info)
Preclinical evaluation of newly approved and potential antiepileptic drugs against cocaine-induced seizures.
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Seizures and status epilepticus are among the neurological complications of cocaine overdose in humans. The aim of the present study was to evaluate the protective effectiveness and therapeutic index (separation between anticonvulsive and side effect profiles) of 14 newly approved and potential antiepileptic drugs using a murine model of acute cocaine toxicity and the inverted-screen test for behavioral side effect testing. Cocaine (75 mg/kg i.p.) produces clonic seizures (approximately 90% of mice), and conventional antiepileptic drugs have been reported to be either ineffective or only effective at doses producing significant sedative/ataxic effects. Clobazam, flunarizine, lamotrigine, topiramate, and zonisamide were ineffective against seizures up to doses producing significant motor impairment. In contrast, felbamate, gabapentin, loreclezole, losigamone, progabide, remacemide, stiripentol, tiagabine, and vigabatrin produced dose-dependent protection against cocaine-induced convulsions with varied separations between their anticonvulsant and side effect profiles: the protective index values (toxic TD(50)/anticonvulsive ED(50)) ranged from 1.26 (felbamate) to 7.67 (loreclezole), and gabapentin had the highest (protective index >152). Thus, several drugs were identified with greater protective efficacy and reduced motor impairment compared with classic antiepileptic drugs. Based on the proposed mechanism of action of these new anticonvulsants, it is noteworthy that 1) drugs that enhance gamma-aminobutyric acid-mediated neuronal inhibition in a manner distinct from barbiturates and benzodiazepines offer the best protective/behavioral side effect profiles, and 2) functional antagonists of Na(+) and Ca(2+) channels are generally ineffective. Overall, this study provides the first description of the effectiveness of new antiepileptic drugs against experimentally induced cocaine seizures and points to several drugs that deserve clinical scrutiny for this indication. (+info)
Structural requirement of the calcium-channel subunit alpha2delta for gabapentin binding.
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Gabapentin [Neurontin, 1-(aminomethyl)cyclohexaneacetic acid] is a novel anticonvulsant drug with a high binding affinity for the Ca(2+)-channel subunit alpha(2)delta. In this study, the gabapentin-binding properties of wild-type and mutated porcine brain alpha(2)delta proteins were investigated. Removal of the disulphide bonds between the alpha(2) and the delta subunits did not result in a significant loss of gabapentin binding, suggesting that the disulphide linkage between the two subunits is not required for binding. Singly expressed alpha(2) protein remained membrane associated. However, alpha(2) alone was unable to bind gabapentin, unless the cells were concurrently transfected with the expression vector for delta, suggesting that both alpha(2) and delta are required for gabapentin binding. Using internal deletion mutagenesis, we mapped two regions [amino acid residues 339-365 (DeltaF) and 875-905 (DeltaJ)] within the alpha(2) subunit that are not required for gabapentin binding. Further, deletion of three other individual regions [amino acid residues 206-222 (DeltaD), 516-537 (DeltaH) and 583-603 (DeltaI)] within the alpha(2) subunit disrupted gabapentin binding, suggesting the structural importance of these regions. Using alanine to replace four to six amino acid residues in each of these regions abolished gabapentin binding. These results demonstrate that region D, between the N-terminal end and the first putative transmembrane domain of alpha(2), and regions H and I, between the putative splicing acceptor sites (Gln(511) and Ser(601)), may play important roles in maintaining the structural integrity for gabapentin binding. Further single amino acid replacement mutagenesis within these regions identified Arg(217) as critical for gabapentin binding. (+info)
Upregulation of the hyperpolarization-activated cation current in rat thalamic relay neurones by acetazolamide.
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1. The effect of inhibition of brain carbonic anhydrase (CA) on the hyperpolarization-activated cation current (Ih) of thalamocortical (TC) neurones of the rat ventrobasal thalamic complex (VB) was investigated in an in vitro slice preparation using the whole-cell patch-clamp technique and fluorescence ratio imaging of the pH indicator 2',7'-bis(carboxyethyl)-5(and -6)-carboxyfluorescein (BCECF). 2. Recording of Ih before and after addition of 0.4-0.8 mM acetazolamide to the bathing fluid revealed a significant shift in the voltage dependence of activation (V ) of 5-7 mV to more positive potentials. 3. Simultaneous recording of Ih and BCECF fluorescence ratio (F420/F495) revealed an increase in Ih amplitude accompanied by an intracellular alkalinization upon application of acetazolamide. The CA inhibitor ethoxyzolamide (EZA, 50 microM) also led to an intracellular alkalinization and a subsequent 4-5 mV positive shift of V of Ih. 4. Acetazolamide and EZA both profoundly slowed the rapid fall of pHi upon switching from Hepes- to CO2/HCO3--buffered superfusate, indicating intracellular CA isoforms in TC neurones. 5. In slices bathed in Hepes-buffered saline, addition of acetazolamide had no effect on the amplitude and time course of activation of Ih, indicating that the action of acetazolamide on Ih was dependent on the presence of HCO3-. 6. Under current-clamp conditions, the neuronal response to hyperpolarizing current pulses in the presence of acetazolamide was decreased as compared to control. This resulted in a strongly reduced ability of TC neurones to produce rebound Ca2+-mediated spikes. 7. The present results implied that in TC neurones acetazolamide led to an intracellular alkalinization which causes, due to its pH sensitivity, an increase in Ih. (+info)
Estrogen supplementation for bone dematuration in young epileptic man treated with anticonvulsant therapy; a case report.
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We encountered a young man treated with anticonvulsant therapy who had greatly reduced bone mineral density. An 18-year-old man was admitted to our hospital for shoulder pain and further evaluation of decreased bone mineral density. He had been treated with anticonvulsants, including phenytoin, phenobarbital, valproic acid and zonisamide for seizures. Although testosterone was found within the normal range for adult men, the serum estrogen concentration was below the detection limit (< 10 pg/ml) and his wrist epiphyses were not yet closed. After 10 months of treatment with the conjugated estrogen, both his height and weight showed improvement, while his bone mineral density and bone age were increased. These findings suggested that estrogen therapy had a significant effect on his skeletal growth and bone maturation in man. This is the first report showing the beneficial effect of estrogen supplementation in an epileptic man receiving treatment with anticonvulsants. (+info)
The role of CYP2C19 in the metabolism of (+/-) bufuralol, the prototypic substrate of CYP2D6.
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Upon characterization of baculovirus-expressed cytochrome P-450 (CYP) 2C19, it was observed that this enzyme metabolized (+/-) bufuralol to 1'hydroxybufuralol, a reaction previously understood to be selectively catalyzed by CYP2D6. The apparent K(m) for this reaction was 36 microM with recombinant CYP2C19, approximately 7-fold higher than for recombinant CYP2D6. The intrinsic clearance for this reaction was 37-fold higher with CYP2D6 than for CYP2C19. The involvement of human CYP1A2 in bufuralol 1'-hydroxylation was also confirmed using the recombinant enzyme. Using S-mephenytoin as an inhibitor, the K(i) for inhibition of recombinant CYP2C19-mediated bufuralol hydroxylation was 42 microM, which is the approximate K(m) for recombinant CYP2C19-mediated S-mephenytoin metabolism. The classic CYP2D6 inhibitors quinidine and quinine showed no inhibition of CYP2C19-catalyzed bufuralol metabolism at concentrations that abolished CYP2D6-mediated bufuralol metabolism. Ticlopidine, a potent inhibitor of CYP2C19 and CYP2D6, inhibited bufuralol 1'-hydroxylation by each of these enzymes equipotently. In human liver microsomes that are known to be deficient in CYP2D6 activity, it was shown that in the presence of quinidine, the K(m) shifted from 14 to 38 microM. This is consistent with the K(m) determination for recombinant CYP2C19 of 36 microM. In human liver microsomes that have high CYP2D6 and CYP2C19 activity, the K(m) shifted to 145 microM in the presence of S-mephenytoin and quinidine, consistent with the K(m) determined for CYP1A2. This data suggests that bufuralol, and possibly other CYP2D6 substrates, have the potential to be metabolized by CYP2C19. (+info)
Calcium phosphate stones during long-term acetazolamide treatment for epilepsy.
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We report a case of recurrent renal calculi containing calcium phosphate associated with long-term acetazolamide treatment for epilepsy. Unfortunately, the cause of stone formation was not recognised for many years, by which time irreversible renal damage had occurred. (+info)