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At least 469 records · Page 26Linked to original sources

Simple GLC analysis of anticonvulsant drugs in commercial dosage forms.

A simple, specific GLC procedure is described for the analysis of one sedative and six anticonvulsant drugs in pharmaceutical dosage forms. Sample aliquots of ethotoin, glutethimide, mephenytoin, methsuximide, and phensuximide were shaken with or extracted into ethyl acetate, diluted with the internal standard (diphenyl phthalate) solution, injected into a gas chromatograph, and eluted from a methylsilicon column. Primidone and phenytoin samples (extracted as the free acid) required derivatization with N,O-bis(trimethylsilyl)acetamide prior to chromatography. The same temperature programming conditions and flow rate settings were used for all seven drugs. The GLC results agreed well with those obtained using the pharmacopeial methods.

Anticonvulsants↗

Essential tongue tremor.

Twenty patients with tongue tremor associated with essential tremor are reported. Patients were unaware of the tongue tremor, and voice disturbance was a complaint in only one patient. Three patients had an isolated tongue tremor. Hand tremor was present in 16 patients. Dystonia, myoclonus, and tremor of other body parts were present in some patients. Three patients had a mild-to-moderate dysarthria. The frequency of tongue tremor (4-8 Hz) was identical to hand tremor. The intravenous infusion of ethanol suppressed tongue tremor. Therapy with propranolol, primidone, or clonazepam also reduced tongue tremor amplitude. Tongue tremor is a common finding in some essential tremor patients but often there are no symptoms.

Adolescent↗

A double-blind trial of isoniazid for essential tremor and other action tremors.

We conducted a double-blind trial of isoniazid in 11 patients with essential tremor and four patients with other types of postural action tremor. The tremor had not been helped by beta-blockers or primidone. Isoniazid was given in doses up to 1,200 mg daily, together with 100 mg pyridoxine, for four weeks. Results were assessed with subjective and objective scales. Only two patients with essential tremor appeared to benefit enough to continue the drug after the trial, and only one has benefited from its long-term use. Isoniazid may be useful in rare cases of essential tremor, but must be monitored carefully because of its toxicity.

Adrenergic beta-Antagonists↗

Simultaneous recording of pupillary hippus and EEG. Report of a case.

Pupillary hippus was observed and recorded in a man of 44 years, who had epileptic seizures, chronic alcoholism with liver disease and Primidon intoxication, during a period of unconsciousness of 24 h. During this time the simultaneous records of the EEG and pupillogram over a long period of time revealed that the basic EEG rhythm and hippus had the same frequency. Both recordings were temporarily in phase, time-locked, and could be blocked by painful and acoustic stimuli. The etiology and interpretation of hippus are discussed.

Adult↗

A rapid gas liquid chromatography method for simultaneous determination of various anticonvulsants.

The purpose of this study was to develop a rapid GLC method for the simultaneous determination of the following anticonvulsants: Carbamazepine, Diphenylhydantoin, Phenobarbital, and Primidone. Using a metal column (OV-17) with flash heater methylation as well as high N2 flow-rate, a quantitative methylation of the above anticonvulsants was obtained. A selective temperature program proved to be the decisive factor in separating the various methylated anticonvulsants. The GLC program was completed within 13 min. This method permits a rapid, simultanous and quantitative determination of various important anticonvulsants.

Anticonvulsants↗

Single drug therapy for intractable epilepsy.

Single drug therapy with either phenytoin or primidone resulted in complete seizure control in 11 of 35 patients (31%) referred to an epilepsy clinic for treatment of uncontrolled chronic epilepsy with complex-partial seizures. Complete seizure control was associated with an increase in the mean plasma concentrations from 14 micrograms/ml to 23 micrograms/ml phenytoin and from 34 micrograms/ml to 40 micrograms/ml phenobarbitone with no change in the antiepileptic drug. Insufficiently low plasma concentrations of less than 11 micrograms/ml phenytoin or phenobarbitone were measured at the first visit in 14 patients (40%). Non-compliance was admitted by eight patients (23%). Optimum single drug therapy is of considerable clinical value in intractable epilepsy with complex-partial seizures.

Adult↗

Therapeutic aspects of kinesiogenic paroxysmal choreoathetosis and familial paroxysmal choreoathetosis of the Mount and Reback type.

Six generations of a family with paroxysmal choreoathetosis of the Mount and Reback type were studied. Neurological investigation and follow-up of the symptoms were possible for four generations, in which 15 members suffered from the disease. The attacks could be provoked by alcohol and intensified by caffeine or emotional excitement. Phenytoin, primidone and carbamazepine had no therapeutic effect. Treatment with L-dopa could provoke the choreoathetosis. Haloperidol was the most effective treatment and valproic acid was also able to reduce drastically the frequency and intensity of the attacks. Three patients with sporadic kinesiogenic, paroxysmal choreoathetosis were also studied, whose choreoathetosis was induced by movement. Treatment with carbamazepine or phenytoin was effective, but haloperidol increased the severity of the choreoathetoid attacks.

Adolescent↗

[The frequency of adult anticonvulsant osteomalacia in relation to duration of therapy and dosage of anticonvulsants (author's transl)].

Of 837 epileptics over 16 years of age treated with mono- or combined hydantoin therapy 20.3% showed radiographic signs of anticonvulsant osteomalacia. With the exception of the patients with severe disturbances of the skeletal system no positive correlation was found with duration of therapy. The percentage of moderate bone changes was the highest in the patients treated for 1 to 2 years; the percentage of severe bone changes in the group treated over 10 years. The rate of osteomalacia correlated with the total dose of hydantoin, phenobarbital, or primidone; the correlation with the dose per year was even more evident. The risk of osteomalacia rose distinctly with doses over 3000 equivalent units/year. The patients with combined hydantoin-barbiturate treatment showed a higher risk than those treated with phenytoin alone. The rate of osteomalacia was the highest in the patients aged under 20 years and over 50 years. Males showed a relatively higher rate of osteomalacia than females, they were treated however with a higher dose per year. The chemical parameters blood alkaline phosphatase and 25-hydroxycholecalciferol corresponded to the radiographic signs, whereas calcium and anorganic phosphate showed no correlation. Early routine radiologic and chemical control especially of the epileptic patients with high risk of osteomalacia should be routinely performed in future.

Adult↗

Na(+)-dependent biotin transport into brush-border membrane vesicles from human kidney cortex.

Renal reabsorption of biotin was investigated in human kidney by means of the isolated brush-border membrane vesicle technique. Biotin uptake into the vesicles was sodium-dependent producing a typical overshoot when incubated under sodium-gradient conditions (external concentration greater than internal). This effect was not observed in the presence of gradients of KCl, LiCl or choline-chloride, nor in the absence of any salt. Using the K+/valinomycin voltage-clamp method biotin uptake remained uninfluenced, i.e. was electroneutral, whereas glucose uptake (which is known to be electrogenic in kidney of other species) was greatly increased. When biotin transport was investigated as a function of external sodium concentration a stoichiometic coupling factor of 1 for the Na(+)-biotin- cotransport was determined. Increasing the biotin concentration in the incubation medium up to 200 mumol/l led to saturation with the kinetic parameters of 31 mumol/l for the apparent Michaelis constant and 82 nmol g protein-1 30 s-1 for the maximal transport rate. Uptake was not saturable in the concentration range of 0.001-1 mumol/l. Inhibition of the biotin uptake (25 mumol/l) was observed in the presence of 250 mumol/l dethiobiotin, bisnorbiotin, thioctic acid, and probenecid, whereas biocytin, propionic acid, lactic acid, succinic acid, citric acid, ascorbic acid, primidone and carbamazepine had no effect. We conclude that renal biotin reabsorption in human kidney is specifically sodium-dependent, saturable and electroneutral. It therefore fulfills the requirements for a secondary active carrier-mediated transport system. The results suggest that biocytin is not an inhibitor of renal biotin reabsorption.

Biomarkers↗

Carbamazepine, phenytoin and phenobarbital in drug-resistant partial epilepsies.

96 monotherapies with carbamazepine, phenytoin, phenobarbital and primidone were assessed in 42 patients with partial epilepsy. Those whose seizure frequency was reduced by 75% or more were considered to have improved. In 54 comparisons of monotherapies significant improvement in seizure frequency was achieved in only 16.7% of cases. Nonresponding patients showed practically no change across all comparisons according to the Fischer test.

Adolescent↗

Optimization of solid-phase microextraction procedures for the determination of tricyclic antidepressants and anticonvulsants in plasma samples by liquid chromatography.

Simple, sensitive, and reproducible off-line solid-phase microextraction and liquid chromatography (SPME/LC) methods are described for the determination of seven anticonvulsants and tricyclic antidepressants in human plasma. Factorial design and simplex methodology were applied in the optimization of the SPME procedure for tricyclic antidepressants analyses. Important factors in the SPME efficiency are discussed, such as the fiber coatings (both lab-made and commercial), extraction time, pH, ionic strength, influence of plasma proteins, and desorption conditions. The development of the lab-made fiber coatings, namely, octadecylsilane, aminosilane, and polyurethane, are further described and applied to anticonvulsants analyses. The investigated plasmatic range for the evaluated anticonvulsants, using CW-TPR fiber, were the following: phenylethylmalonamide (3.00-40.0 microg mL(-1)), phenobarbital (5.00-40.0 microg mL(-1)), primidone (3.00-40.0 microg mL(-1)), carbamazepine and carbamazepine-epoxide (2.00-24.0 microg mL(-1)), phenytoin (2.00-40.0 microg mL(-1)), and lamotrigine (0.50-12.0 microg mL(-1)). The antidepressants' linear plasmatic concentration ranged from 75.0 to 500 ng mL(-1) for imipramine, amitriptyline, and desipramine, and from 50.0 to 500 ng mL(-1) for nortriptyline, being in all cases, the limit of quantification represented by the lowest value. The precision (interassays) for all investigated drugs in plasma sample spiked with different concentrations of each analyte and submitted to the described procedures were lower than 15%. The off-line SPME/LC methodologies developed allow anticonvulsants and antidepressants analyses from therapeutic to toxic levels for therapeutic drug monitoring.

Amitriptyline↗

Pharmacologic interactions between valproate and other drugs.

Valproate is often administered with other antiepileptic drugs, a practice that can lead to clinically significant pharmacologic interactions. Concomitant administration of such enzyme-inducing antiepileptic drugs as carbamazepine, phenobarbital, primidone, or phenytoin will markedly accelerate the metabolic conversion of valproate, particularly in children. In response to the effects of enzyme induction, valproate dosage may need to be doubled to maintain therapeutic serum levels. Valproate does not appear to induce enzymatic drug metabolism, but rather acts as a metabolic inhibitor. Because of this inhibition, phenobarbital dosage must often be reduced after valproate is added to the therapeutic regimen. Valproate also may markedly increase concentrations of the active epoxide metabolite of carbamazepine. The interaction between phenytoin and valproate results primarily from displacement from plasma proteins. The resulting increase in the free fraction of phenytoin alters the relationship between total phenytoin concentration and the drug's pharmacologic effect. Thus, clinical evidence of toxicity may be present at concentrations usually considered to be in the therapeutic range.

Anticonvulsants↗

Cerebrospinal fluid and plasma glutamine elevation by anticonvulsant drugs: a potential diagnostic and therapeutic trap.

Administration of phenobarbitone or primidone can produce an elevation of glutamine and ornithine concentrations, together with a reduction of urea concentrations, in the fasting plasma and CSF of some infants, and in the CSF of some older epileptic patients. These two anticonvulsant drugs may interfere with the metabolic conversion of ammonia to urea, possibly by enzyme inhibition at the step of carbomoyl phosphate synthesis. The elevation of glutamine in plasma and CSF can mimic values found in some hyperammonemias. Recognition of this drug reaction can prevent erroneous diagnoses of genetically-determined urea cycle disorders and subsequent inappropriate therapy.

Adolescent↗

Quality control in the simultaneous assay of anticonvulsants using an automated gas chromatographic system with a nitrogen detector.

An automated gas-liquid chromatographic technique for the routine determination of phenobarbitone, primidone and phenytoin using a nitrogen-detector is described. The high selectivity of the detector for nitrogen-containing compounds allows a direct extraction procedure and the use of a phenytoin analogue as an internal standard obviates the need for accurate aliquot measurement after extraction. The anticonvulsants are chromatographed as methyl derivatives produced by on-column methylation with trimethylphenyl ammonium hydroxide following automatic liquid injection. Quality control data from an internal quality control scheme is presented and the performance of the laboratory in an inter-laboratory control scheme is reported and discussed.

Anticonvulsants↗

An improved method for preparation of samples for the simultaneous assay of some antiepileptic drugs by gas-liquid chromatography.

A new simple extraction method, e.g., for subsequent quantitative determination of some antiepileptic drugs by GLC is described. HCl and an internal standard are added to 100 microliter of plasma or any biological fluid. This mixture is applied directly to an Extrelut column. Lipophilic substances (i.e. the antiepileptic drugs diphenylhydantoin, primidone and phenobarbital) are then extracted into 20 ml of ether and the solvent is evaporated to dryness. Direct GLC analysis of the on-column methylated drugs is performed using a P-N-detector.

Barbiturates↗

An improved method for perfusion of the isolated brain of the rat-influence of perfusion conditions and application of analeptic and anticonvulsant drugs.

A method for the perfusion of the isolated brain of the rat with synthetic fluorocarbon emulsion is described. The functional states of the brains were investigated using biochemical, biophysical, and histological methods. After 4.5 h of perfusion, all brains were in excellent condition and comparable to the in vivo state. The influence of perfusion conditions on the viability of the brains was studied. Deep hypothermia was well tolerated; at 13 degrees the EEG exhibited a mean frequency of about 8 Hz, while the mean amplitude was about 40% lower than at 28 degrees or 36 degrees. Constant-pressure perfusion did not affect brain function, provided that the pressure amplitude was very slowly decreased. During application of pentylenetetrazole (PTZ) it was found that the threshold concentration of PTZ in the perfusion medium to induce epileptic seizure discharges was 0.13 mg/ml. However, after repeated application of PTZ, the threshold concentration decreased exponentially, indicating a kindling phenomenon. It could be shown that not PTZ as such, but the spike potentials provoked by PTZ, induced the kindling effect. This was inhibited by application of primidone or phenobarbital.

Adenosine Triphosphate↗

Automated analysis of antiepileptic drugs in serum by column-switching high-performance liquid chromatography.

An automated high-performance liquid chromatographic column-switching system is presented for the analysis of antiepileptic drugs in serum. Initial results show that a reversed-phase extraction column works best overall when fitted with screens versus frits, and when packed with porous 30-micron particles as opposed to a pellicular packing of similar size or with smaller porous particles. The continuous analysis of primidone for over 2000 serum samples is achieved at a rate of twelve samples per hour with a single analytical column. An analogous boxcar high-performance liquid chromatographic system is also assembled and used to analyze two of four injected antiepileptic drugs at a rate of 40 samples per hour. For 1000 of these analyses, the coefficient of variation is 1% without an internal standard.

Anticonvulsants↗

Concurrent determination of valproic acid with other antiepileptic drugs by high-performance liquid chromatography.

We describe a method for the simultaneous determination of valproic acid with four other antiepileptic drugs (phenobarbital, phenytoin, carbamazepine, and primidone) in plasma by high-performance liquid chromatography. These drugs are extracted from plasma by adding a small volume of acetonitrile following saturation with ammonium sulphate. An aliquot of the extract is then injected on a reversed-phase column with a methanol-water mobile phase. The total time required for the whole analytical process including the plasma pretreatment and chromatography is approximately 20 min. The assay method is simple, rapid, reproducible and specific, and considered, therefore, suitable for both emergency and routine uses in monitoring these antiepileptic drugs simultaneously.

Anticonvulsants↗