Primidone Research Articles

レーザーイムノケミカルシステム（ｉ‐ＰｉＴ）による血中プリミドン濃度測定法の検討

A new reagent kit for serum primidone (PMD) assay by laser immunochemical system (i-PiT) was developed. This kit is different from the former kits in that it uses a drug-linked latex, which reacts with antibody to bring about agglutination and, according to the manual, blank test is unnecessary in the process of assay. First, we confirmed the ground for the omission of blank test in some experiments, and then studied the precision, accuracy and other features of i-PiT method using the reagent kit for serum PMD assay.The precision of i-PiT method without blank test applied to three-PMD-level specimens of patients, expressed as coefficient of variation, was not less than 8.0% of within-day and not more than 6.0% of between-run. Mean recovery of PMD was 101.2%. Moreover, to study the accuracy, PMD concentration in the sera of 20 patients was determined by i-PiT and EMIT methods. The correlation coefficient and the regression line were 0.978 and y= 0.983x+ 0.181 (y: i-PiT, x: EMIT), respectively.In consideration of the omission of blank test, precision and accuracy, the new reagent kit for serum PMD assay of i-PiT method is considered to be one of the useful reagent kits for determination of serum drug concentration in hospital laboratories.

Interactions between anticonvulsants and other commonly prescribed drugs.

Many drug interactions can be demonstrated, but only a few are so clinically significant that they necessitate adjusting drug dosages. The same drug combination may produce changes of variable extent or direction in different individuals. The reasons for this variability include genetic control of the rate and inducibility of drug metabolism, and environmental factors such as contact with chemicals. Among antimicrobial agents, chloramphenicol may cause accumulation of phenytoin (PHT) and phenobarbital (PB), and isoniazid may cause PHT, carbamazepine (CBZ), and primidone (PRM) to accumulate. Erythromycin may cause accumulation of CBZ. Among anti-ulcer agents, antacids may reduce PHT concentration while cimetidine may cause accumulation of PHT, CBZ, and diazepam (DZP). Salicylates displace strongly binding drugs such as PHT, DZP, or valproate (VPA) from the binding sites in plasma proteins, which may lead to some decline of the total plasma level with an increase in the unbound drug percentage. Conversely, anticonvulsants may influence the dosage requirements of oral anticoagulants by inducing their metabolism. Failures of oral contraceptives have been attributed to anticonvulsants in some patients. Probably the most predictable interaction that necessitates dosage adjustment is accumulation of PB caused by VPA. Intentional inhibition of PRM metabolism by nicotinamide serves as an example of attempts to utilize an interaction for improved therapeutic effect.

Single-dose kinetics of primidone in acute viral hepatitis.

The pharmacokinetics of primidone (PRM) after oral administration of a single 500 mg dose was studied in 7 patients with acute viral hepatitis and 7 healthy control subjects. The elimination half-life and the apparent clearance of unchanged PRM in the patients were 18.0 +/- 3.1 h and 42 +/- 14 ml X h-1 X kg-1, respectively (mean +/- SD) and did not differ significantly from the values in the controls (half-life 17.0 +/- 2.4 h; clearance 35 +/- 8 ml X h-1 X kg-1). The metabolite phenylethylmalonamide (PEMA) was detected in the serum of all normal subjects within 2-24 h. By contrast, serum levels of this metabolite were undetectable (less than 2 mumol/1) in all but one of the patients. Serum levels of phenobarbital (PB) remained below the limit of detection (less than 2 mumol/1) in all subjects. The findings indicate that accumulation of PRM with its attendant toxicity is unlikely to occur in epileptic patients who develop acute viral hepatitis, despite evidence that the metabolism of the drug is affected by this condition. The possibility of impaired conversion to PB and its implications are discussed.

Development of tolerance to the side effects of primidone.

Side effects and antiepileptic drug levels were measured during initiation of and chronic treatment with primidone (PRM). A significant change in the toxicity/serum level ratio was observed 6 h after the initial PRM dose. The amount of toxicity manifested by patients receiving PRM as their initial antiepileptic drug was not different from that of those patients previously treated with phenytoin (PHT) or carbamazepine (CBZ). These findings indicate rapid development of functional tolerance to side effects of PRM, which is not altered by previous exposure to PHT or CBZ. Phenobarbital pretreatment appears to produce cross-tolerance to the effects of PRM.

Effectiveness and Toxicity of Phenobarbital, Primidone, and Sodium Valproate in the Prevention of Febrile Convulsions, Controlled by Plasma Levels

The effectiveness and toxicity of phenobarbital (PB), primidone (PRM), and sodium valproate (VPA), used exclusively in monotherapy, were compared in 95 children affected with febrile convulsions. Treatment was restricted to either complicated or simple febrile convulsions with risk factors. The effectiveness and toxicity of each drug were related to the daily dose and the steady-state plasma levels. PB (4.8 +/- 0.7 mg/kg/day) achieved plasma levels of 16.4 +/- 2.8 micrograms/ml and prevented febrile convulsions in 80% of the patients. Side effects were observed in 76.7% of the patients, a change in dose being required only in 13.3%. PRM (17.8 mg/kg/day) yielded PB plasma levels of 14.1 +/- 3.7 micrograms/ml and was effective in 88.2% of the patients. The incidence of side effects was 53%, but no change in treatment was required. VPA (35.2 +/- 5.9 mg/kg/day) achieved plasma levels of 57.2 +/- 15.3 micrograms/ml (measured before the first dose in the morning) and was effective in 91.7% of the patients. Side effects were detected in 45% (significantly lower than after PB, p less than 0.01), and required a change in treatment in 14.3%. No differences in doses and plasma levels were found between patients with or without recurrence of febrile convulsions and with or without side effects; an exception was the higher doses of VPA administered to patients who showed side effects. It is concluded that PRM and VPA were at least as effective and well tolerated as PB. Because the plasma levels of the three drugs were near the lower limit of the therapeutic range, it remains to be elucidated whether higher doses may increase the benefit without adding unacceptable toxicity.

On the Reliability of Substrate-labeled Fluorescent Immunoassay for the Determination of Blood Concentration of Primidone

Primidone (PRM) concentrations in patients' serum as well as in spiked serum samples determined by the methods of high-performance liquid chromatography (HPLC), homogeneous enzyme immunoassay (EMIT) and fluorescence polarization immunoassay (FPIA) were compared in order to examine the reliability of the manual and semiautomatic (SLFIA) method using AMES TDA antiepileptic drug kit. Results showed that both of the SLFIA techniques are useful means for the determination of blood concentrations of PRM in epileptic patients to satisfy the clinical requirements.

Primidone, phenobarbital, and PEMA: II. Seizure protection, neurotoxicity, and therapeutic index of varying combinations in mice.

Neurotoxicity and protection against maximal electroshock (MES) and pentylenetrazol (Metrazol) seizures were determined in mice for various combinations of primidone (PRM), phenobarbital (PB), and phenylethylmalonamide (PEMA). The results suggest that PRM and PB together are superior to either one alone in terms of spectrum of activity and relative toxicity. The protection against Metrazol and the toxicity of PB are both potentiated by PEMA at low concentrations. PEMA also potentiates the toxicity of combined PRM plus PB, without altering their protection against MES, thus lowering their therapeutic index. We conclude that PRM and PB together have an advantage over PB alone, especially when their brain concentration ratio is at or above 1 and PEMA concentrations are low. These conditions are usually not present at steady state in patients treated with PRM.

Primidone, phenobarbital, and PEMA: I. Seizure protection, neurotoxicity, and therapeutic index of individual compounds in mice.

Neurotoxicity and protection against maximal electroshock and Metrazol seizures from primidone (PRM), phenobarbital (PB), and phenylethylmalonamide (PEMA) were determined in mice for each drug separately and expressed in terms of brain concentrations. Compared with PB, PEMA was 16 times less potent against electroshock and Metrazol seizures but only 8 times less toxic. Primidone was markedly less neurotoxic than PB and equally potent against electroshock, but PRM had no effect against Metrazol or bicuculline. PRM is a relatively nontoxic anticonvulsant with a different action than PB, and PEMA is both a weak and a relatively toxic anticonvulsant.

Simultaneous determination of several antiepileptic drugs and its clinical application to some cases of multiple-drug administration

The simplified method for the determination of phenytoin (DPH), phenobarbital (PHB), carbamazepine (CBZ), primidone (PRM), valproic acid (VPA), and ethosuximide (ES) was established. In this method, the serum containing these drugs was acidified and extracted with chloroform containing hexobarbital and cyclohexanecarboxylic acid as internal standards. Then, some aliqout of the extract was evaporated to dryness in vacuo, and DPH, PHB, CBZ, and PRM were simultaneously determined by a high-performance liquid chromatography. While, isoamylacetate was added to the other aliqout of the extract, and chloroform was evaporated in vacuo, then VPA and ES were simultaneously determined by a gas-liquid chromatography. These relatively simple procedures gave enough accuracy to determine the serum levels of these drugs in epileptic patients with multipledrug administration. Some cases of the antiepileptic medication were also described in this report. In an epileptic patient, the ratio of cerebrospinal/serum levels of PHB was increased by coadministration of acetazolamide.

Diphenylhydantoin and primidone in tears.

Diphenylhydantoin (PHT) and primidone (PRM) were determined by the EMIT technique in the plasma, tears, saliva, and CSF of epileptic patients. Results indicate for PHT that tear values are more strictly correlated than are the saliva values to plasma and CSF concentrations. As for PRM, the data obtained show great interindividual variability of concentration in the different body fluids--in agreement with the wide range of both protein binding and half-life of this drug.

Primidone kinetics: effects of concurrent drugs and duration of therapy.

Primidone (PRM) kinetics was examined in two groups of adult seizure patients: (1) 10 newly diagnosed in whom only PRM was used, the monotherapy (MT) group, and (2) nine in whom PRM was added to other antiepileptics, the combination therapy (CT) group. Time-concentration data were obtained after an initial dose of 250 mg and during subsequent steady-state periods. PRM elimination was slower (p less than 0.05) after the initial dose in MT patients (half-life (t 1/2) = 15.2 hr, apparent clearance = 35 ml/hr/kg) than in CT patients (t 1/2 = 8.3 hr, clearance = 51 ml/hr/kg). PRM metabolites, phenobarbital and phenylethylmalonamide, appeared much earlier in CT patients. Continued PRM exposure in MT patients was accompanied by an increase in apparent clearance in three of seven patients, but no change in four of seven. In four CT patients in whom other antiepileptics were withdrawn there was a decrease in apparent clearance (61.4 to 29.9 ml/hr/kg) no rates in the range of MT patients. PRM kinetics is influenced by concurrent antiepileptic drugs and by duration of PRM therapy.

Integrated Method for the Gas Chromatographic Determination of Antiepileptic Drugs in Human Plasma

Summary: The principles of three independent extraction methods were utilized to develop an integrated extraction scheme for use in routine therapeutic monitoring of seven antiepileptic agents. The final method, in which the three extraction methods were interfaced, permitted routine monitoring in a single 1 ml volume of human plasma of any one or combination of the following drugs: phenytoin (PHT), phenobarbital (PB), primidone (PD), 5-ethyl-5-phenylhydantoin (EPH), ethosuximide (ES), carbamazepine (CBZ), and valproic acid (VPA). An on-column methylation technique was used for simultaneous determination of PHT, PB, PD, EPH, and ES. CBZ and VPA were determined by independent methods as the underivatized compounds. Six appropriate internal standards were employed in the integrated method for quantitation of the drugs.

Integrated Method for the Gas Chromatographic Determination of Antiepileptic Drugs in Human Plasma

The principles of three independent extraction methods were utilized to develop an integrated extraction scheme for use in routine therapeutic monitoring of seven antiepileptic agents. The final method, in which the three extraction methods were interfaced, permitted routine monitoring in a single 1 ml volume of human plasma of any one or combination of the following drugs: phenytoin (PHT), phenobarbital (PB), primidone (PD), 5-ethyl-5-phenylhydantoin (EPH), ethosuximide (ES), carbamazepine (CBZ), and valproic acid (VPA). An on-column methylation technique was used for simultaneous determination of PHT, PB, PD, EPH, and ES. CBZ and VPA were determined by independent methods as the underivatized compounds. Six appropriate internal standards were employed in the integrated method for quantitation of the drugs.

Effect of anticonvulsant and antidepressant drugs on iodothyronines in serum.

Serum iodothyronine concentrations were measured in patients on long-term therapy with one or two anticonvulsant drugs. Diphenylhydantoin (DPH) and carbamazepine (CBZ) reduced the serum levels of thyroxine (T4) free T4 index, reverse triiodothyronine (rT3) and 3,3'-diiodothyronine (3,3'-T2), whereas the depressant effect on the serum levels of triiodothyronine (T3) and free T3 index was small but statistically significant. In patients administered DPH and phenobarbital (PB) or CBZ and primidone (PD) the serum iodothyronine levels were also depressed, except for normal T3 and free T3 index. Patients receiving only PB or PD had normal serum levels of total and free thyroid hormones, but decreased concentrations of rT3 and 3,3'-T2. Only supratherapeutic concentrations of DPH and CBZ added in vitro to control sera significantly reduced the number of T4 and T3-binding sites, as reflected in increased T4 and T3 uptake test results. This indicates that the DPH and CBZ-induced decrease in thyroid hormone concentrations in vivo is not due to a displacement of thyroid hormones from their binding sites on serum proteins. The antidepressant drugs amitriptyline and mianserin had no effect on the thyroid hormone levels in serum.

Single‐dose pharmacokinetics and anticonvulsant efficacy of primidone in mice

The pharmacokinetics and efficacy of the anticonvulsant primidone (PRM) and its active metabolites, phenobarbital (PB) and phenylethylmalonamide (PEMA), were studied after single-dose administration in mice. The half-life of PB is twice that of PRM and PEMA. The plasma/brain ratios provide evidence of poor penetration of PRM into brain. The results support our findings of negligible or absent PRM concentrations in the brains of patients on primidone therapy who were undergoing surgery for intractable epilepsy. The anticonvulsant properties of PRM, PB, and PEMA against maximal electroshock in mice were also studied with the use of the metabolic inhibitor SKF 525A. The half-life, potency, peak anticonvulsant effect, and effective dose curves of these compounds indicate that the anticonvulsant effect of short-term oral PRM administration in mice is from derived PB.

Gas chromatographic on-column methylation technique for the simulataneous determination of antiepileptic drugs in blood.

An on-column methylation technique (OCMT) is described for the simultaneous, gas chromatographic determination in blood of ethosuximide (ES), phenobarbital (PB), primidone (PD), phenytoin (DPH), and 5-ethyl-5-phenylhydantoin (EPH). Multiple internal standards are employed in the OCMT, in order to eliminate or to minimize greatly error sources common to the technology of gas chromatography and to compensate for the different chemical dispositions of the antiepileptic drugs in an OCMT. The internal standards used in the OCMT were as follows: alpha,alpha,beta-trimethylsuccinimide (TMS) was used for the determination of ES; 5-ethyl-5-para-tolylbarbituric acid (MPB), for PB; 5-ethyl-5-(para-tolyl) hexahydropyrimidine-4,6-dione (MPD), for PD; and 5-(para-tolyl)-5-phenylhydantoin (MPPH), for EPH and DPH. The use of ether, the buffering of the plasma sample at pH 7.6, and the use of dilute (0.30-0.35 M) trimethyl-phenylammonium hydroxide (TMPAH) contributed to the specificity of the extraction scheme of the OCMT. The precision and accuracy of the OCMT was attributed to the use of appropriate, multiple internal standards. A method is described for the preparation of standard solutions of drugs in blank plasma (biological matrix) and for the use of the standards in calibration and daily intra-laboratory control of the OCMT.

Primidone intoxication in a child.

Aim: Determination of the prevalence, of the radiological and clinical characteristics, and outcome of atypical hyperplasia (AH) of the breast within a population subjected to routine screening (double-view mammography with double reading, performed every two years between 50 and 75 years of age). Patients and Methods: The clinical and radiological records and histological findings of percutaneous and surgical biopsy specimens of sixty-eight patients presenting with AH were reviewed together with patient follow-up data after percutaneous and surgical biopsy. Results: AH incidence in the population was 0.19‰ with the following distribution of lesions: atypical epithelial hyperplasia (AEH, 53%), columnar cell metaplasia with atypia (CCMA, 32%), and lobular intraepithelial neoplasia (LIN, 8%). The mean patient age was 58 years and 24% of patients were receiving hormone replacement therapy. The main radiological finding was the presence of microcalcifications for AEH and CCMA lesions in particular, and the mammograms were valid (correlation between American College of Radiology score and risk of lesion, only 3% of lesions were recognized on the second reading). A total of 13.7% of AH cases were underestimated and a real risk of AH progression was observed, regardless of whether or not surgical biopsy had been performed. Conclusion: The clinical and radiological characteristics of AH observed in a population subjected to routine breast cancer screening are identical to those for patients with the same lesions referred to specialist centers. Surgical biopsy remains the recommended option due to the risk of underestimation of lesions by percutaneous biopsy and the risk of progression justifies the need for continued close monitoring.

Lesions in folic acid metabolism induced by primidone.

Les auteurs ont etudie le mecanisme de la toxicite de la primidone (Mysoline) chez certains microorganismes. Ces recherches montrent que le metabolisme de l'acide folique est inhibe par le primidone et cela en trois etapes: (a) la reduction de l'acide folique en acide dihydrofolique, (b) le metabolisme des pteridines nonconjugees et (c) la phosphorylation de la thymidine.

Primidone treatment of athetosis in children.

Primidone treatment of athetosis in children.

Treatment of acute primidone poisoning with bemegride and amiphenazole.

Treatment of acute primidone poisoning with bemegride and amiphenazole.