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PubMedDate not supplied

Identification of p-hydroxyprimidone as a minor metabolite of primidone in rat and man.

Urine specimens from rats and humans who received single doses of primidone (PRM) have been investigated by GC/MS procedures. In addition to the previously documented metabolites of PRM, a small chromatographic peak was encountered which had a mass spectrum suggesting a hydroxy-PRM derivative. Synthesis of p-hydroxy-PRM from PRM was effected; the para isomer was separated from unwanted isomers by preparative HPLC. The PMR spectrum of the synthetic compound proved the position of the hydroxy substituent to be para. This compound had identical GC retention time and an almost identical mass spectrum with that obtained in the urinary extracts. Para-hydroxy-PRM was therefore confirmed as a new, minor metabolite of PRM in rat and man.

Adult↗
PubMed1984

Simultaneous measurement of ethosuximide, primidone, phenobarbital, phenytoin, carbamazepine, and their bioactive metabolites by liquid chromatography.

A simple, isocratic liquid-chromatographic method was developed for simultaneously measuring ethosuximide, primidone, phenobarbital, phenytoin, carbamazepine, and their bioactive metabolites within 10 min. The chromatographic system involves a Waters' Radial-NOVA PAK C18 reversed-phase column and acetone/methanol/acetonitrile/10 mmol/L phosphate buffer (10/21/8/61 by vol, pH adjusted to 7.95 with NaOH) as mobile phase. The antiepileptic drugs are extracted from 50 microL of serum by mixing with 50 microL of acetonitrile containing 10 mg of tolybarb per liter as internal standard. After centrifugation, 20 microL of the supernate is injected onto the column and eluted with mobile phase at the rate of 2.8 mL/min at ambient temperature. The column effluent is monitored at 200 nm. The method can detect the five antiepileptic drugs in concentrations as low as 0.5 mg/L. Analytical recovery ranges from 98 to 102%. Within-run CV ranged from 2.9 to 5.8% and between-run CV from 4.7 to 7.1%. The method can also be used to measure N-desmethyl-methsuximide, chloramphenicol, and pentobarbital.

Anticonvulsants↗
PubMed1983

PB:PRM ratio in patients with epilepsy treated with primidone.

Phenobarbitone (PB) and primidone (PRM) plasma concentrations were measured in 88 patients of both sexes with different types of epilepsy and treated with PRM, alone or in association with carbamazepine (CBZ), phenytoin (PHT), ethosuximide (ESM) or valproic acid (VPA). A correlation was observed between the dose and the levels of both PRM and PB. Plasma PB:PRM ratio was high variable, especially interindividually. These changes seemed to be linked to age and particularly to pharmacological associations. In fact, PB:PRM ratio was increased with CBZ, ESM, VPA and PHT respectively. Moreover, a correlation was observed between the PB:PRM ratio and PHT plasma levels. The possibility of monitoring PB and PRM plasma levels during long-term treatment with PRM is discussed.

Adolescent↗
PubMed1983

Simultaneous very fast liquid-chromatographic analysis of ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine in serum.

We describe a sensitive, specific, and very fast liquid-chromatographic assay for simultaneously determining five anticonvulsants (ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine) by using commercially available 5- or 3-microns particle size reversed-phase columns and a microflow-cell-equipped ultraviolet detector. The anticonvulsant drugs are extracted from 200 microL of serum containing 50 mg of cyclopal per liter as an internal standard, by elution from a Bond-Elut (Analytichem International, Harbor City, CA 90710) column with 300 microL of methanol. A 5-microL aliquot of the eluate is applied to an analytical column and eluted with a mobile phase of acetonitrile/methanol/phosphate buffer, 20 mmol/L, pH 3.7 (13.5/35/51.5 by vol), at a flow rate of 3.0 mL/min and at 50 degrees C. Detection is at 210 or 195 nm. The chromatography is complete in less than 2.5 min with the 5-microns-particle column, and in less than 1.4 min with the 3-microns-particle column. The sensitivity of the method for all drugs is less than 1 mg/L. Analytical recovery of drugs added to serum ranged from 92 to 109% for concentrations up to 200 mg/L. Between-run precision (CV) ranged from 1.3 to 4.1%.

Carbamazepine↗
PubMedDate not supplied

[Primidone kinetics and analysis of its interactions with the major antiepileptic drugs].

In 5 volunteers, after single oral administration of 10 mg/Kg of primidone (PRM) plasmatic concentration of the drug has been monitored during 24 hours. PRM plasma half life was found longer than in previous reports. It was however confirmed that its metabolite phenobarbital (PB) is not present in the blood for at least 48 hours. Moreover 166 patients under long term PRM treatment were investigated as to the influence of phenytoin (DPH) and carbamazepine (CBZ) on the PB serum levels. It was found that patients in therapy with PRM + DPH showed a better relationship between PRM oral dose and PB plasma level and also between oral dose and plasma level of DPH than in patients in monotherapy with PRM or DPH, whereas these effects were not evident in patients taking PB + DPH.

Administration, Oral↗
PubMed1982

Improved isocratic liquid-chromatographic simultaneous measurement of phenytoin, phenobarbital, primidone, carbamazepine, ethosuximide, and N-desmethylmethsuximide in serum.

We describe an improved "high-pressure" liquid-chromatographic assay for simultaneous determination in serum of the five major antiepileptic drugs (ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine) and N-desmethylmethsuximide (the compound that must be quantitated for therapeutic drug monitoring of the antiepileptic drug methsuximide). Serum protein is precipitated with an acetone solution containing 5-ethyl-5-(p-methylphenyl)barbituric acid as the internal standard. The centrifuged supernate is injected onto the chromatographic column. Drugs and internal standard are eluted at 30 degrees C with mobile phase containing acetonitrile/methanol/phosphate buffer (17/28/55 by vol) at a flow rate of 0.7 mL/min, monitored at 195 nm. Analysis time is about 20 min. Quantitation is by measurement of peak areas. Analytical and absolute recoveries varied from 95 to 104%. Within-day coefficients of variation ranged from 1.6 to 5.4%, between-day CVs from 0.0 to 3.4% in subtherapeutic, therapeutic, and toxic samples. Resolution of therapeutic concentrations of all six drugs was complete. As yet, we have found no drug or drug metabolite that interferes.

Carbamazepine↗
PubMed1980

Monitoring 2-ethyl-2-phenylmalonamide in serum by gas-liquid chromatography: application to retrospective study in epilepsy patients dosed with primidone.

We describe a procedure for determining 2-ethyl-2-phenylmalonamide (I) in serum of epilepsy patients dosed with primidone (II) for seizure control, by extracting the sample with chloroform under basic conditions, with use of an internal standard, 2-ethyl-2-(p-tolyl)malonamide, and without derivative formation. The sensitivity limit is 1.0 mg/L. Within-run CVs for 5, 10, and 30 mg/L concentrations were 3.5, 2.5, and 0.7%, respectively. For a 1.0 mg/kg body wt per day dose of II in patients co-medicated with phenytoin (Group A), the mean steady-state concentrations of I, II, and phenobarbital (III) were 0.72, 0.62, and 2.24 mg/L, respectively. For patients co-medicated with carbamazepine and phenytoin (Group B), I, II, and III concentrations were 0.68, 0.44, and 2.12 mg/L, respectively. Between these groups, only for II were the concentrations statistically different (t = 2.762; p < 0.01). For Group A no correlation was found between II and III. For Groups A and B, the coefficients of correlation between I and III were 0.626 and 0.826, respectively.

Adult↗
PubMed1976

Synthesis and characterization of alpha-phenyl-gamma-butyrolactone, a metabolite of glutethimide, phenobarbital and primidone, in human urine.

A novel metabolite, alpha-phenyl-gamma-butyfolactone has been isolated in urine samples of patients severely intoxicated by either glutethimide, phenobarbital, or primidone. This lactone was prepared synthetically and its spectral data and chromatographic properties were compared to those data obtained from the urine samples of drug overdosed victims. The results of these comparisons confirm the presence of this lactone in human urine following the ingestion of large amounts of the parent drug.

Glutethimide↗