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H Reith

Publications and source records attributed to H Reith.

11 recordsLinked to original sources
PubMed1993

Diffusion analysis of valproate and trans-2-en-valproate in agar and in cerebral cortex of the rat.

The diffusion of valproate (VPA) and trans-2-en-valproate were studied in agar gel and in the cerebral cortex of the rat using pressure microejection and VPA-selective microelectrodes. From the agar measurements a free diffusion coefficient for VPA of 6.52 x 10(-6) cm2.s-1 and for trans-2-en-VPA of 5.25 x 10(-6) cm2.s-1 for 37 degrees C was determined. The tortuosity value in the cortex was 1.92 for VPA and 1.67 for trans-2-en-VPA. The tortuosity values suggest that VPA and trans-2-en-VPA diffuse mainly in the extracellular space of the brain.

Agar↗
PubMed1993

Effects of valproate on early and late potassium currents of single neurons.

The effects of valproate sodium (VPA) on potassium currents were tested in identified neurons of the snail Helix pomatia. VPA was extracellularly and intracellularly applied. VPA (i) had no effects on the current-voltage relation of the early potassium outward current (IA), (ii) shifted the steady state inactivation function of IA to more positive potentials, (iii) increased the amplitude of the late potassium outward currents. It is suggested that the extrasynaptic effects on potassium currents markedly contribute to the antiepileptic and antimanic effects of VPA.

Animals↗
PubMed1977

[On the enteral absorption of valproic acid (author's transl)].

The absorption of valproic acid (dipropylacetic acid, DPA)--administered by capsules (free valproic acid) and dragees (valproate sodium)--has been studied. Regarding their bioavailability, both forms of administration examined are equivalent, which means that they are representing therapeutical alternatives.

Biological Availability↗
PubMed1977

[Problems in serum-level determination during valproic acid therapy].

An investigation was carried out to determine whether or not a reliable and reproducible steady state serum level of the anticonvulsant drug valproic acid could be found, such that single values of a serum level determination could be used in therapeutic control. 1. A reliable and comparable serum concentration of valproic acid could not be found in 11 patients during a long-term investigation over a period of 8 weeks. Likewise this could not be found in the 24-h serum concentration profile in 8 of the above mentioned patients, who were receiving both mono and combined therapy. 2. The half-life values for valproic acid in these 8 patients lay between 8--12.5 h. 3. The maximum concentration of valproic acid lies in unforeseeable time spans after drug administration. 4. The morning fasting values are comparable only to a limited extent. In future daily profiles it must be decided whether, and if so to what extent, valproic acid serum concentration determinations can be of value to the individual treatment of epileptics.

Adolescent↗
PubMed1975

[Infusion of phenytoin concentrate in a child (author's transl)].

In a four-year-old boy receiving phenytoin for seizures, the phenytoin blood level after 1000 mg phenytoin given over 24 hours alternatively intravenously (600 mg) and intramuscularly (400 mg) was found to be 14.7 mu g/ml. After 12 hours of intravenous infusion of 750 mg phenytoin concentrate the concentration was 18.7 mug/ml. When 750 mg phenytoin were given over more than 18 hours the phenytoin blood level was only 7.4 mug/ml.

Age Factors↗
PubMedDate not supplied

Effects of valproate in a model nervous system (buccal ganglia of Helix pomatia): I. Antiepileptic actions.

Cellular actions of valproate (VPA) were studied using intracellular recordings of identified neuronal individuals in the buccal ganglia of Helix pomatia. Under nonepileptic conditions, VPA induced (a) a hyperpolarization, (b) slight changes in action potentials (AP), and (c) an increase in membrane resistance. Under epileptic conditions (i.e., during application of an epileptogenic drug), extracellular application of VPA decreased frequency of occurrence of epileptic depolarizations (early effect) and led to a decay in paroxysmal depolarizations (late effect). Intracellular injection of VPA could block epileptic activity in the treated neuron immediately. A metabolite of VPA (trans-2-en VPA) mainly lacked the late effect (decay in epileptic depolarizations) obtained with VPA. Results suggest that the early antiepileptic effect is exerted from the extracellular side of the neuronal membrane and that the late effect results from intracellular actions of VPA being delayed by slow access to an intracellular site.

Action Potentials↗
PubMedDate not supplied

Effects of valproate in a model nervous system (buccal ganglia of Helix pomatia): II. Epileptogenic actions.

High concentrations of valproate (VPA; greater than 20 mM) depolarized identified neuronal individuals in the buccal ganglia of Helix pomatia and transiently induced paroxysmal depolarization shifts (PDS). Threshold concentration of VPA for the induction of PDS was decreased (a) by increased seizure susceptibility, (b) by increased concentrations of derivatives of VPA, and (c) by increased H+ concentrations. Intrasomatic injection of VPA did not induce PDS. The epileptogenic action of VPA is believed to be exerted from the extracellular side of the cell membrane.

Animals↗