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Time-dependent kinetics III: diurnal oscillations in steady-state plasma valproic acid levels in rhesus monkeys.

Valproic acid was administered by constant rate intravenous infusion to catheterized chained rhesus monkeys for 8-10 weeks under controlled environmental conditions. Steady-state plasma levels were monitored at 2-hr intervals for 26 hr (10 am-12 noon on the following day), 1 day/week for 6 weeks. Individual steady-state plasma concentration-time plots exhibited the following characteristics. During Period A (10 am-6 pm), plasma levels remained stable or decreased. During Period B (6 pm-6 am), plasma levels increased, reached a maximum, and remained markedly higher than during Period A. The maximum concentrations were 40-140% higher than the observed minimum concentrations. During Period C (6 am-noon), plasma levels tended to decline from the maximum concentrations achieved in Period B. In most cases, plasma concentrations at 10 am and 12 noon of the 2nd experimental day fell within 10% of their respective values on the previous day. The mean (+/- SD) periods obtained by cross-correlation analysis of individual plasma concentration-time plots were 30.7 (+/- 3.7) and 22.8 (+/- 3.6) hr for Animals 903 and 923, respectively. The corresponding mean (+/- SD) amplitudes were 27.3 (+/- 12.6) and 17.4 (+/- 2.3)%. A circadian rhythm in total body clearance was hypothesized, and its pharmacokinetic implications are discussed.

Animals↗

[The effect of dipropyl acetic acid (Convules) in epileptic adults with a high frequency of seizures].

The anti-convulsive action of dipropyl acetic acid (Convulex) was tested in 21 patients with grandmal seizures (GM) and/or temporal lobe attacks (TL), or with Jacksonian epilepsy. Patients were chosen according to a negative selection system. Results showed that in GM and TL seizures, Convulex constitutes an important addition to the battery of anticonvulsives available today. Action was more potent in GM than in TL attacks. Toxic effects are slight. Treatment had to be discontinued in two patients -- once because of cerebellar symptoms and once because of crowded incidence of seizures. In two cases the patients gained weight. Occasional gastrointestinal complaints disappeared when antacids were administered. No changes were observed with reference to blood count, or to hepatic or renal function. Fatigue set in only when treatment was combined with barbiturates and disappeared again when pre-medication was reduced. Five patients showed an improved state of mind (activation and better communication with others); this psychological action may be considered an additional advantage. Since the action of barbiturates and hydantoins is potentiated by Convulex, pre-medication may be reduced --provided Convulex therapy alone does not seem adequate. Hence, trial treatment with Convulex may also be recommended in those patients who are successfully controlled with barbiturates and hydantoins,but whose daily work schedule is impaired due to fatigue.

Adult↗

Disposition of valproic acid in man.

The pharmacokinetics of valproic acid (VPA) have been studied in 6 healthy subjects following a single 600 mg dose, and after multiple doses over 12 days (1200 mg daily) of enteric-coated sodium valproate. A time lag before absorption of 1 to 2 h was observed in each subject, and then absorption was rapid, peak concentrations being recorded 3 to 4 h after administration of the dose. The plasma level decline was biphasic with a terminal half-life of 15.9 +/- 2.6 h in the single dose and 17.3 +/- 3.0 h in the multiple dose experiments. There was no evidence of dose dependent kinetics or autoinduction. Total plasma clearance was 0.0064 +/- 0.0011 l/kg X h. The apparent volume of distribution was small at 0.15 +/- 0.2 l/kg. The mean steady state plasma concentration (Css) reached after 4 days was 81.3 +/- 13.0 microgram/ml. Css observed was lower than Css predicted (99.2 +/- 14.7 microgram/ml) from single dose kinetics (p less than 0.001). The difference was probably due to a reduction in plasma protein binding at higher concentrations. VPA concentration in saliva was between 0.4 and 4.5% of the total plasma concentration and was not equal to the concentration of unbound drug in plasma (6.7 +/- 0.8% unbound). 3.2% of the dose was excreted in urine as the parent drug and 21.2% as conjugated metabolites.

Adult↗

Sodium valproate and clonazepam in the treatment of intractable epilepsy.

Of 88 patients with intractable epilepsy, 60 have been treated with clonazepam for up to three years and 60 have been treated with sodium valproate for up to 18 months. Each agent was used sequentially in an overlapping group of 32 patients. Both agents have proven effective in the control of petit mal absences and myoclonic jerks, although some patients responded to one and not to the other. Clonazepam has given better results than valproate in temporal lobe and other partial (focal) epilepsies, while valproate has given better results in grand mal seizures and atonic attacks. Both preparations were more effective in patients with spike and wave paroxysms in their EEG recordings, the correlation being more conspicuous with valproate. Both medications appear to be safe and useful additions to anticonvulsant therapy.

Adolescent↗

Valproate sodium in Huntington chorea.

An open trial of valproate sodium in 14 patients suffering from Huntington chorea showed that the drug was ineffective in the two treatment schedules employed.

Adolescent↗

Comparison of ocular disposition of free pivalic acid and pivalic acid esterified in dipivefrin.

Dipivefrin, a diester of pivalic acid and epinephrine that is used in the treatment of glaucoma, has been shown to be hydrolyzed in the cornea, and the ocular pharmacokinetics of the active moiety, epinephrine, have been determined. A comparison of the ocular disposition of the pivalic acid released by hydrolysis of dipivefrin and that of topically applied free pivalic acid showed that the released pivalic acid is not metabolized in the eye and is rapidly eliminated from the eye with no apparent sequestration in ocular tissues. In addition, results of two methods for preparing ocular tissues for analysis of drug distribution indicated that freezing and thawing processes can lead to redistribution of materials in ocular tissues.

Animals↗

Origin of nitrogen in the biosynthesis of carbamoylpolyoxamic acid.

The biosynthetic origin of the carbamoylpolyoxamic sidechain of the polyoxin nucleoside peptide antibiotics was studied using 15N labeled alpha-amino-S-hydroxyvaleric acid as precursor. Gas chromatography mass spectrometry of polyoxamic acid isolated from culture filtrates of Streptomyces cacaoi var. asoensis showed incorporation of the nitrogen atom of alpha-amino-S-hydroxyvaleric acid into carbamoylpolyoxamic acid with an isotopic dilution factor of 23, thus establishing the intermediacy of alpha-amino-S-hydroxyvaleric acid and determination of the full biosynthetic pathway.

Amino Acids↗

The identification of 3-keto-2-methylvaleric acid and 3-hydroxy-2-methylvaleric acid in a patient with propionic acidemia.

Two abnormal metabolites, 3-keto-2-methylvaleric acid and 3-hydroxy-2-methylvaleric acid, have been identified and quantitated in the urine of a child with propionic acidemia. These metabolites may be produced as a result of the self-condensation of propionyl-CoA. Data are presented to show that the unusual ketone, 3-pentanone, which has been observed previously in the urine of patients with propionic acidemia, is produced as a result of the decarboxylation of 3-keto-2-methylvaleric acid.

Gas Chromatography-Mass Spectrometry↗

Pharmacokinetics of di-n-propylacetate in epileptic patients.

The pharmacokinetics of the anti-epileptic drug di-n-propylacetate (DepakineR) have been studied in 7 patients, in whom plasma concentrations were determined during and following subchronic treatment. Elimination of the drug appeared to follow a monophasic exponential course; biological half lives were 8 to 15 hours. The data supported the assumption that an open one-compartment model can be used to describe the kinetics of dipropylacetate in man. The drug appeared to have a relatively restricted distribution: calculated relative distribution volumes ranged from 0.15 to 0.40 1/kg. There were large interindividual differences in clearance rate. The therapeutic range was considered to be between 50 and 100 mg/1 plasma. Plasma levels of phenobarbital were markedly raised during treatment with dipropylacetate for an unknown reason. Determination of the plasma concentrations of drugs at accurately fixed times appears to be a reliable method for pharmacotherapeutic monitoring of epileptic patients.

Administration, Oral↗

Effects of 4-pentenoic acid and furosemide on renal functions and renal uptake of individual free fatty acids.

1. Effects of 4-pentenoic acid (4-PA), an inhibitor of fatty acid oxidation, on renal fatty acids (FFA) were investigated using mongrel dogs, and the results compared with findings in the case of furosemide. 2. Continuous infusion of 4-PA at a rate of 0.66 mumoles/kg.min into the renal artery resulted in a marked reduction of glomerular filtration rate after 45 min. Sodium reabsorption rate tended to decrease at 30 min and a significant decrease was seen after 45 min. With decrease in the renal sodium reabsorption rate, the urine flow increased about 3 times, and there was a marked natriuresis. 3. Concentrations of individual FFA in the arterial and renal venous plasma were determined by gas-liquid chromatographic analysis. In the control period, data from 25 dogs showed renal uptake of palmitic, stearic, oleic, and linoleic acids to be approximately 40, 15, 25, and 10 nmoles/g.min, respectively, and the uptake of palmitic and oleic acids was depressed during the natriuresis following administration of 4-PA and furosemide. 4. These results suggest that fatty acids play an important role in the energy supply in renal tubular sodium transport.

Animals↗

Influence of gemfibrozil on high-density lipoproteins.

In animal studies, gemfibrozil markedly elevates high-density lipoprotein (HDL) cholesterol levels. In humans with primary hyperlipoproteinemia and lipoprotein phenotypes IIA, IIB and IV, gemfibrozil, 1,200 mg/day, was associated with a 25%, 20% and 17% increase in HDL cholesterol, respectively. Gemfibrozil also substantially increased the ratio of HDL to total cholesterol, reflecting both an increase in HDL cholesterol and a decrease in very low density lipoprotein cholesterol and low-density lipoprotein cholesterol. Compared with a placebo in subjects with types IIA, IIB and IV lipoprotein phenotypes, therapy with gemfibrozil led to an increase of 33%, 34% and 23%, respectively, in the ratio of HDL cholesterol to total cholesterol. With gemfibrozil therapy, about 80% of subjects with hypertriglyceridemia had a reduction in triglycerides of 35% or a return to normal levels; 50% of subjects with hypercholesterolemia had a cholesterol reduction of 20% or a return to normal levels.

Animals↗