Relationship between tolerance to GABAA agonist and bursting properties in neocortical neurons during GABA-withdrawal syndrome

The interruption of intracortical, chronic GABA infusion is known to give rise to 'GABA withdrawal syndrome' (GWS) consisting of electroencephalographic paroxysmal focal activities, associated with behavioral epileptic signs. Neocortical slices were obtained from rats presenting the GWS (GWS slices), and intracellular recordings were performed in the vicinity of the gamma-aminobutyric acid (GABA)-infused site. Electrical stimulation of the underlying white matter induced paroxysmal depolarization shifts (PDSs) in virtually all neurons. Bath-applied GABA (1-10 microM) had no effect on these neurons, while the same dose range was found effective in blocking action potentials in saline-infused cortex slices obtained from control rats. In the GWS slices a population of neurons presented, in addition to synaptically induced PDSs, voltage-dependent and cobalt-sensitive PDSs and bursts of action potentials induced by depolarizing current injections. These intrinsic bursting neurons were unresponsive to high doses of GABA (100 microM). Dose-response curves of isoguvacine, a specific GABAA agonist, showed a shift to the right for the intrinsic bursting cells whatever the parameter measured (depolarization or conductance increase): the ED50 was 50-100 times higher for intrinsic bursting cells than for other non-intrinsic bursting cells, thus indicating that intrinsic bursting cells are tolerant to GABAA agonist. This tolerance may result from a decreased number of receptors or from a change in their properties as a consequence of the previous prolonged GABA infusion. The decrease in the GABA efficacy could lead to disinhibition and could thus give the appearance of epileptic events.

[Effect of fenibut and seduxen on fetal development in the second half of pregnancy]

In experiments on rats it was found that fenibut (50 mg/kg, 1/20 of LD50) during a single and repeated administration in the fetus period of pregnancy does not exert any negative effect on the maternal organism, the growth and development of the fetus. Seduxen administered in a dose of 50 mg/kg (1/80 of LD50) alone and in combination with fenibut was shown to decrease the female body weight gain and to disturb the fetus development. Following a single administration on the 17th day of pregnancy, the effect was poorly pronounced.

[Metabolic acidosis and hypoglycemia during calcium hopantenate administration--report on 5 patients]

Calcium hopantenate (HOPA) has been widely used as an activator of cerebral metabolism in Japan. However, several cases of acute encephalopathy during HOPA administration were recently reported, which were characterized by marked metabolic acidosis and hypoglycemia. The encephalopathy in these patients was named Reye-like syndrome because of the similarity to Reye's syndrome in children. The purposes of this presentation are to report on 5 patients with acute encephalopathy developing during HOPA administration, to summarize their symptoms and clinical courses, and to discuss the pathogenesis of metabolic acidosis and hypoglycemia. Initial characteristics of the clinical course in all patients were loss of appetite, nausea and vomiting, followed by unconsciousness. Laboratory examinations revealed marked metabolic acidosis, severe hypoglycemia, hyperlactacidemia, leukocytosis, ketonuria, and increased Ht and BUN. A few days after development of the initial symptoms, mild renal and liver dysfunction, and elevation of serum amylase were observed in all patients. Hyperlactacidemia was present in 4 in the initial period. Blood concentration of HOPA was 2.131 micrograms/ml in patient 1 (8-10 hours after final administration), and 10.7 micrograms/ml in patient 5 (24 hours after final administration). These values are extremely high, because usually HOPA concentration is almost negligible 7 hours after the drug is taken. As the pathogenesis of acute encephalopathy due to HOPA administration, the failure of fatty acid beta-oxidation has been proposed by some investigators. However, the serum concentrations of CoA, pantothenic acid and carnitine during the initial stage were not reduced in our patients. Furthermore, it is very difficult to explain the severe hypoglycemia in terms of the beta-oxidation theory.(ABSTRACT TRUNCATED AT 250 WORDS)

Reye-like syndrome following treatment with the pantothenic acid antagonist, calcium hopantenate

Three senile patients developed fatal acute encephalopathy while receiving calcium hopantenate. The clinical, biochemical, and pathological picture was similar to Reye's syndrome. Calcium hopantenate is a pantothenic acid antagonist. The serum levels of calcium hopantenate were high in coma, and that of pantothenic acid examined in one patient was lowered. Evidence obtained indicated that the Reye-like syndrome might be caused by calcium hopantenate possibly due to the induction of pantothenic acid deficiency.

Submassive hepatic necrosis associated with the use of progabide: a GABA receptor agonist

Progabide, a recently introduced gamma-aminobutyric acid mimetic, is currently undergoing clinical evaluation for a variety of convulsive disorders. We describe a patient in whom severe hepatic failure developed after four weeks of Progabide therapy. The patient's course was marked by encephalopathy, jaundice, hypoglycemia, markedly elevated serum aminotransferase levels, and prolongation of the prothrombin time. Liver biopsy showed extensive hepatocellular necrosis. The patient recovered slowly after discontinuation of the drug. The finding of eosinophilia and increased serum IgE suggests an immunologically mediated mechanism for the Progabide-induced hepatic injury. Alternatively, the lipophilic moiety of Progabide may interact with hepatocyte cell membrane lipids leading to toxic injury. We conclude that Progabide may occasionally cause severe hepatic injury.

Effects of long-lasting antiepileptic therapy on brainstem auditory evoked potentials

The brainstem auditory evoked potentials of 84 epileptic patients in chronic monotherapy with carbamazepine (n = 36), phenobarbital (n = 19), Na-valproate (n = 20) or progabide (n = 9) were studied. The mean values of I-III and I-V interpeak latencies (IPLs) were respectively 2.16 +/- 0.11 and 4.03 +/- 0.17 in the control group, 2.31 +/- 0.09 and 4.17 +/- 0.16 in the valproic group, 2.30 +/- 0.17 and 4.19 +/- 0.20 in the carbamazepine group, 2.17 +/- 0.16 and 4.10 +/- 0.18 in the phenobarbital group and 2.16 +/- 0.11 and 4.12 +/- 0.17 in the progabide group. The prolongation of I-III and I-V IPLs was statistically significant only for the valproic acid and carbamazepine groups. Neither duration of the epilepsy and treatment and frequency of seizures nor the serum drug levels were correlated with I-V IPL values.

The GABA-agonist progabide for spasticity in multiple sclerosis

Thirty-two patients with spasticity due to multiple sclerosis were entered into a randomized, double-blinded, placebo-controlled crossover trial of the gamma-aminobutyric acid agonist, progabide. Each patient was treated with a maximum of 45 mg/kg of progabide during each of two four-week treatment periods, separated by a two-week washout. Twenty-five participants completed the study; seven failed to complete the study due to adverse events. Progabide was associated with lessened spasticity. There was no loss of motor power associated with progabide. The physician, patients, and study nurse coordinator all declared preferences for progabide for treatment of spasticity. Ten participants (40%) chose to remain on progabide in an open, long-term follow-up protocol. Seven serious adverse events occurred. One consisted of fever and weakness without infection; the other six consisted of elevated aspartate aminotransferase and alanine aminotransferase levels, four of which were asymptomatic. All adverse events resolved entirely when the drug was stopped. Progabide is an effective antispastic agent and its antispastic effect is not accompanied by increased motor weakness. The use of the drug, however, is associated with a high incidence of adverse events, which will likely limit progabide's therapeutic usefulness.

Preliminary evaluation of the effect of GABA and phosphatidylserine in epileptic patients

The effect of the combined administration of gamma-aminobutyric acid (GABA) and phosphatidylserine was evaluated in a pilot study of 42 patients with drug-resistant epilepsy. The group included patients with complex partial seizures, simple partial seizures and absence seizures. Patients with complex partial seizures and simple partial seizures showed no significant improvement; on the other hand, there was a remarkable decrease in absence seizures, linearly related to the dose of GABA and phosphatidylserine. Side effects occurred in 9 patients and were usually mild.

Epileptogenic gamma-aminobutyric acid-withdrawal syndrome after chronic, intracortical infusion in baboons

We studied the effects of chronic (7 days) infusion of GABA (100 micrograms/microliter) applied intracortically into the fronto-rolandic (FR) area of baboons, via osmotic minipumps. In photosensitive animals, bilateral GABA application produced a complete blockade of the paroxysmal discharges and associated clinical signs induced by intermittent light stimulation. Unilateral administration had similar effects, although these developed more gradually. At the end of the infusion period, both photosensitive and non-photosensitive animals showed a transitory state (3-4 days) of cortical hyperexcitability (spontaneous epileptogenic activity) localized to the infused area. The data indicate a role of GABA both in the natural photosensitivity of the epileptic baboon and in the withdrawal syndrome consecutive to the sudden interruption of chronically enhanced GABA levels in the FR territories of this monkey.

Long-term treatment of epilepsy: open multicenter trial with progabide in epileptic patients

A long-term open multicenter trial was carried out in 15 European centers with therapy-resistant epileptics to evaluate the efficacy and safety of progabide, a new antiepileptic GABA receptor agonist; 187 patients, suffering from partial epilepsy (57%), primary generalized epilepsy (20%), secondary generalized epilepsy (21%), and unclassified generalized epilepsy (2%), participated in the study. All patients had a total seizure frequency higher than one per month in spite of standard antiepileptic medication; 46% had a mean partial seizure frequency from daily to weekly. Progabide was administered at a mean daily dose of 30.5 mg/kg/day as an add-on to the standard antiepileptic drugs up to one year in 115 patients; 37 patients (19.8%) dropped out because of reasons which were not drug-related (bad compliance, lost to follow-up); in 12 patients (6.5%) progabide was withdrawn for side effects and in 20 (10.7%) for lack of efficacy. 71.3% of patients treated for one year (62% considering the 'cumulative' number of patients) experienced more than a 50% reduction in seizure frequency. This reduction was equally present in patients with partial epilepsy (63.9%) and with generalized epilepsy (62.2% of patients with primary and 57.1% with secondary generalized epilepsy). No signs of tolerance phenomena to the antiepileptic effect of progabide were observed. No side effects were reported in 56.7% of the patients. Clinical side effects were mild and transient, leading to progabide discontinuation in 6.5% of the patients only; an increase in SGPT was observed in 5.7% of the patients, these increases were transient and without any clinical symptom.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study of progabide, valproate, and placebo as add-on therapy in patients with refractory epilepsy

A three way single blind cross-over comparison of progabide, valproate and placebo, as adjunctive therapy, was undertaken in 64 patients with therapy-resistant partial and generalised seizures. The study was not completed because of the incidence of elevated hepatic enzymes on progabide. Analysis of efficacy showed progabide to be inferior to valproate against all seizure types, particularly against tonic-clonic seizures. Valproate was superior to placebo against all seizure types, partial and tonic-clonic seizures. Progabide did not differ significantly from placebo in any instance. In addition progabide caused elevation of hepatic enzymes which was symptomatic in one case, and was associated with an interaction with phenytoin which resulted in symptoms of intoxication in some cases.

Progabide for refractory partial epilepsy: a controlled add-on trial

Progabide, an experimental GABA-ergic antiepileptic drug, was given in a placebo-controlled double-blind cross-over trial to 19 adult patients with chronic partial epilepsy refractory to previous high-dose antiepileptic drug therapy. A mean daily dose of 32 mg/kg (range, 16 to 63) of progabide did not significantly change the seizure frequency. In patients with a therapeutic response, progabide led to an increase in the plasma concentration of phenytoin and phenobarbital. Comedication with carbamazepine was associated with a poor response to progabide. Side effects were mild except for a several-fold increase of SGOT and SGPT, which required withdrawal of progabide in one patient. Progabide does not seem to be the drug urgently needed for failures of previous high-dose drug therapy.

Acute encephalopathy with hyperammonemia and dicarboxylic aciduria during calcium hopantenate therapy: a patient report

We report a 3-year-old Japanese girl who developed acute encephalopathy while receiving calcium hopantenate (Calcium D-(+)-4-(2, 4-dihydroxy-3,3-dimethylbutyramido) butyrate hemihydrate). She had hyperammonemia, elevated CPK, lactic acidemia and pyruvic acidemia, however, she did not show elevated SGOT or SGPT. Calcium hopantenate has been used in Japan for the treatment of mental retardation with behavior abnormalities. Recently there have been three reports on the occurrence of Reye-like syndrome in patients receiving this drug. Clinical signs and laboratory data of these patients are similar to those of Reye syndrome. Calcium hopantenate causes pantothenic acid deficiency in the young rat, which may reduce the content of coenzyme A. If this drug decreases coenzyme A biosynthesis, it may reduce beta-oxidation of fatty acids and levels of dicarboxylic acids would increase because of increasing omega-oxidation. We suspect that there is a possible relationship between the occurrence of acute encephalopathy and calcium hopantenate therapy.

Progabide treatment in severe epilepsy: a double-blind cross-over trial versus placebo

Twenty therapy-resistant epileptic patients entered a double-blind, randomized, two-period, cross-over trial comparing progabide (19.3-36 mg/kg/day) and placebo as add-on drugs to standard therapy. Each period lasted 6 weeks with a gradual crossover during 4 days. Five patients were dropped because of reasons unrelated to treatment. Among the 15 patients who completed the study, seven had partial, six primary generalized, and two secondary generalized epilepsies. Preexisting antiepileptic drugs (AEDs) ranging from one to three per patient (mean 2.2 AEDs/patient) were maintained unchanged during the trial. Efficacy was assessed biweekly by means of total seizure counts, counts of each seizure type, and global clinical judgment. At the same time intervals, safety was assessed by means of reports of adverse events, clinical and neurological examination, laboratory tests, and measurement of plasma concentrations of progabide and associated AEDs. According to the clinical global judgment, eight patients were considered improved during progabide treatment. Seizures were reduced in 14 of 15 patients during the progabide as compared with the placebo period. During the progabide period, the reduction of the total seizure count was 45 and 58% in two patients and 88-97% in six patients. A significant reduction of the total seizure number was observed in the progabide period as compared with the placebo period, both in the whole patient group (p less than 0.01) and in the two subgroups of patients with generalized (p less than 0.01) and partial (p less than 0.05) epilepsies.(ABSTRACT TRUNCATED AT 250 WORDS)

Progabide as an add-on drug for epilepsy refractory to high dose antiepileptic drug therapy

In a double-blind cross-over add-on trial an average daily dose of 2100 mg progabide or placebo were given for 3 months each as adjunctive therapy to 11 patients with intractable complex partial seizures uncontrolled by a high-dose regimen of either carbamazepine, phenobarbital, phenytoin or primidone. A reduction or an increase in seizure frequency by more than 50% was seen in one patient each. Mild transient sedative side effects were observed in two patients. The plasma concentrations of the concomitant antiepileptic drugs remained unchanged. Progabide appears to be as effective as primary antiepileptic drug for adjunctive therapy in partial epilepsy refractory to previous high-dose therapy. Progabide does not seem to be the drug urgently needed for failures of standard therapy despite its few side effects.

Symptomatic treatment of tardive dyskinesia: a word of caution

The search for a treatment of tardive dyskinesia (TD) has focused largely on cholinergic and GABAergic agents that are believed to attenuate striatal imbalances and bring about symptomatic control of dyskinetic movements. While numerous reports of the partial effectiveness of acute treatment with cholinergic or GABAergic agents have appeared, the effects of chronic administration of these substance are unclear. Results of chronic administration of cholinergic or GABAergic agents to animals are presented, and it is argued that these substances have the potential of eventually worsening TD. Alternative approaches aimed at modifying the theorized pathophysiology of TD, as opposed to symptom control methods, are presented.