Benzodiazepine receptors and their relationship to the treatment of epilepsy

4-Phenyl-1-(prop-2-yn-1-yl)-1H-1,5-benzodiazepin-2(3H)-one

4-Phenyl-1H-1,5-benzodiazepin-2(3H)-one reacts in the pres­ence of a concentrated aqueous solution of sodium hydroxide and a quaternary ammonium salt (as catalyst) in benzene (phase transfer catalysis) with propargyl bromide, affording the title benzodiazepine derivative, C₁₈H₁₄N₂O. In the mol­ecule, the mean plane of the propargyl substituent is almost perpendicular with that of the amide group [dihedral angle = 87.81 (8)°]. In the crystal, the molecules are linked by C—H⋯O and C—H⋯N inter­actions.

[Benzodiazepines in the treatment of epilepsy]

In epilepsy benzodiazepines are mainly used to stop ongoing attacks. In hospitals intravenous diazepam is the drug of choice for status epilepticus. Outside of hospitals buccal midazolam is in the process of replacing rectal diazepam. Clonazepam, clobazam and nitrazepam (to children) are partially used as additional medication to prevent seizures.

Dose-dependent anticonvulsive effect of ethanol on lindane-induced seizures in rats

Chronic ethanol consumption is a major risk factor for epilepsy, and seizures frequently occur during the withdrawal period. The aim of our study was to investigate effects of ethanol on lindane-induced seizures in rats. Male Wistar rats were injected i.p. with one of the following 5 treatments: (i) saline, (ii) dimethylsulfoxide, (iii) lindane (8 mg/kg) (L), (iv) ethanol in doses of 0.5 g/kg (E(0.5)), 1 g/kg (E(1)), and 2 g/kg (E(2)), and (v) groups that received ethanol 30 min before lindane (LE(0.5), LE(1), and LE(2)). Behavioral changes were described by using a descriptive scale as follows: 0, no response; 1, head nodding, lower jaw twitching; 2, myoclonic body jerks, bilateral forelimb clonus; 3, generalized tonic-clonic convulsions; 4, status epilepticus. The incidence of convulsions in the LE(2) group was significantly lower than the incidence in the L (p < 0.01) and LE(0.5) groups (p < 0.05). The median grade of convulsive behavior was significantly lower in the LE(2) (p < 0.01) and LE(1) groups (p < 0.05) compared with the L group. Latencies to the first seizure response were not significantly different among groups. ED50 of ethanol was 1.40 (1.19-1.65). Our findings suggest that ethanol decreased severity and incidence of lindane-induced seizures in a dose-dependent manner.

Clinical pharmacology and mechanism of action of zonisamide

Antiepileptic drugs (AEDs) suppress seizures by selectively modifying the excitability of neurons and blocking seizure firing with minimal disturbance of nonepileptic activity. All AEDs have been shown to work by at least one of 3 main mechanisms of action: through modulation of voltage-gated ion channels, enhancement of synaptic inhibition, and inhibition of synaptic excitation. Zonisamide is a novel AED that has a broad combination of complementary mechanisms of action, which may offer a clinical advantage over other antiepileptic agents. By altering the fast inactivation threshold of voltage-dependent sodium channels, zonisamide reduces sustained high-frequency repetitive firing of action potentials. Zonisamide also inhibits low-threshold T-type calcium channels in neurons, which may prevent the spread of seizure discharge across cells. In addition, zonisamide is a weak inhibitor of carbonic anhydrase. However, this mechanism is not believed to contribute to the antiepileptic activity of zonisamide. Although zonisamide also seems to alter dopamine, serotonin, and acetylcholine metabolism, it is not clear to what extent these effects on neurotransmitters are involved in the clinical actions of the drug. In addition to these actions, recent evidence suggests that zonisamide may exert neuroprotective actions, independent of its antiepileptic activity. These potential effects may be important in preventing neuronal damage caused by recurrent seizures. Therefore, it seems that the multiple pharmacological actions of zonisamide may contribute to the seizure reductions observed in a wide range of epilepsies and may help to preserve efficacy in individual patients despite possible changes in electrophysiological status.

Molecular regulation of glutamate and GABA transporter proteins by clobazam during epileptogenesis in Fe+++-induced epileptic rats

To assess the molecular effects of the antiepileptic drug clobazam (CLB, 1,5-benzodiazepine), a benzodiazepine effective in the management of epilepsy, we performed a series of experiments using rats with chronic, spontaneous recurrent seizures induced by amygdalar injection of FeCl(3). Experimental animals were treated for 14 days with CLB. We then measured the expression of glutamate and GABA transporter proteins and evaluated the changes that occurred in these proteins using both experimental and control animals. CLB treatment was associated with an increase in the production of GLT-1 in the contra-lateral hippocampus of animals receiving amygdalar FeCl(3) and CLB treatment. CLB treatment up-regulated the GABA transporter GAT3 in the contra-lateral hippocampus of animals with chronic, recurrent seizures. In contrast, CLB had no effect on the expression of EAAC1 and GAT1 in the hippocampus or the cortex in control animal groups. Chronic epileptogenesis may be associated with down-regulation of the production of glial excitatory amino acid transporters, GLAST and GLT-1, proteins that cause increase in the basal extracellular concentrations of glutamate. Elevated GABA transporter expression results in increased reverse transport of GABA to the extracellular space during periods of excitation. In addition to allosteric activation of GABA(A) receptors, this study suggests that CLB might exhibit its antiepileptic action by increasing GLT-1 expression and GAT3 in the hippocampus of rats with chronic seizures.

Status epilepticus: clinical analysis of a treatment protocol based on midazolam and phenytoin

The efficacy of a combination of midazolam and phenytoin in treating generalized convulsive status epilepticus in children was studied retrospectively. The patient group comprised all patients admitted for generalized convulsive status epilepticus to the pediatric intensive care unit over 7 years. Patients treated according to the protocol were included (N = 122). These patients were treated with the following regimen; each subsequent step was taken if clinical evidence of epileptic activity persisted: midazolam 0.5 mg/kg rectally or 0.1 mg/kg intravenously. After 10 minutes: midazolam 0.1 mg/kg intravenously. After 10 minutes: phenytoin 20 mg/kg intravenously in 20 minutes. After phenytoin load: midazolam 0.2 mg/kg intravenously followed by midazolam 0.1 mg/kg/hour continuously, increased by 0.1 mg/kg/hour every 10 minutes to maximum 1 mg/kg/hour. Phenobarbital 20 mg/kg intravenously or pentobarbital 2 to 5 mg/kg intravenous load, 1 to 2 mg/kg/hour continuously intravenously. Patients who received initial rectal diazepam were included. Patients were categorized according to the cause of generalized convulsive status epilepticus. These categories were then related to the level of antiepileptic therapy needed. Patients' ages ranged from 0.5 to 197.4 months. The cause of generalized convulsive status epilepticus was idiopathic or febrile convulsions in two thirds of cases. Most (89%) patients were managed on midazolam and phenytoin. Generalized convulsive status epilepticus was terminated with midazolam alone in 58 patients, with the addition of phenytoin in 19 patients and with continuous midazolam in 32 patients. Thirteen patients needed additional barbiturates. The relationship between the level of antiepileptic therapy and etiology was not significant. Fifty-two patients needed artificial ventilation. Seven patients died; no deaths were directly attributable to generalized convulsive status epilepticus itself. With the use of the proposed protocol, combining midazolam and phenytoin, 89% of the cases of generalized convulsive status epilepticus could be successfully managed.

Sedative and anticonvulsant activities of goodyerin, a flavonol glycoside from Goodyera schlechtendaliana

Goodyerin is a flavonol glycoside isolated from the whole plants of Goodyera schlechtendaliana which has been used as a substitute for the crude drug, Anoectochilus formosanus. The pharmacological properties of goodyerin were assayed for effects on spontaneous locomotor activity, on pentobarbital-induced hypnosis, and on anticonvulsant activity against picrotoxin-induced seizures in rodents. Goodyerin exhibited a significant and dose-dependent sedative and anticonvulsant effect.

Proconvulsive effect of tea (Camellia sinensis) in mice

Investigations were carried out to evaluate the effect of acute and chronic administration of both black and green tea on three models of experimentally induced convulsions in mice. Tea extract (both black and green) significantly accelerated the onset of convulsion, increased the duration of convulsion and mortality in mice. Since both the extracts failed to alter the GABA level in brain, based on the earlier report that both black and green tea might act on Ca(2+) channels, it can be suggested that the observed proconvulsive effect of tea is not mediated through GABA but through Ca(2+) channels.

Use of intramuscular midazolam for status epilepticus

Although intravenous (i.v.) administration of antiepileptic drugs is the preferred route of therapy in status epilepticus, intramuscular (i.m.) delivery may provide a valuable alternative when there are obstacles to venous access. Compared to other treatment options such as rectal drug administration, which is as challenging as the i.v. route in a convulsing patient, the i.m. route is easier and less invasive. The two most commonly used first-line anticonvulsants, diazepam and lorazepam, may be administered i.m., but are absorbed from the i.m. site more slowly than midazolam. Midazolam, a fairly new benzodiazepine, is a potent anticonvulsant with a fast onset of effect. Because of its water solubility, midazolam is rapidly absorbed from the injection site and has excellent local tolerability. The pharmacodynamic effects of midazolam can be seen within seconds of its administration, and seizure arrest is usually attained within 5 to 10 min. Case reports and a recent randomized trial that demonstrate the successful use of i.m. midazolam in the termination of epileptic seizures are reviewed.

[125I]iomazenil binding in the brains of spontaneously epileptic rats: an ex vivo quantitative autoradiographic study

Central benzodiazepine receptor binding was studied in spontaneously epileptic rats (SER) and in their parent strain. Kyoto-Wistar (KW) rats, by ex vivo quantitative autoradiography with [125I]iomazenil. Thirteen-week-old SER developed tonic and absence-like seizures following mild stimulation by tapping at 5 min before injection of the radioligand. When compared with age-matched KW rats, a significant 76% elevation of radioactivity was observed in the SER hippocampus, while there was no difference in hippocampal blood flow obtained using [125I]N-isopropyl-p-iodoamphetamine. Since benzodiazepine receptors act to enhance inhibitory GABA transmission, this finding suggests a possible mechanism for seizure-induced enhancement of inhibition.

Central and peripheral benzodiazepine receptors in rat brain and platelets: effects of treatment with diazepam and clobazam

Tolerance to the effects of benzodiazepines (BZ) may be mediated by changes in benzodiazepine receptors (BZRs). Peripheral BZRs (in brain and platelets) and central BZRs (in brain) were measured in rats following intraperitoneal administration of diazepam and clobazam each for 4 and 12 days. BZRs were measured by binding assays using [3H] PK 11195 (peripheral) and [3H] flunitrazepam (central) as radioligands. Diazepam, but not clobazam, increased peripheral BZR numbers in platelets (both P < 0.005), but not in brain, after 4 and 12 days' treatment compared with appropriate controls. Neither drug altered central BZR affinities or numbers in rat brain. BZ effects on peripheral BZRs in platelets cannot be extrapolated to predict changes in brain receptors, either peripheral or central.

Open study of clobazam in refractory epilepsy

Clobazam is a 1,5-benzodiazepine reported to have a wide spectrum of antiepileptic activity and is associated with less neurotoxicity than the 1,4-benzodiazepines, nitrazepam and clonazepam. The effect of clobazam on seizure control and neurologic behavior was examined prospectively in 115 children (average age: 8.4 years) with intractable seizures. Eighteen children (16%) became seizure free and a further 35 (31%) demonstrated a greater than 90% decrease in seizure frequency. Tolerance to the antiepileptic effect of clobazam was observed in 30 of 79 children (38%) who demonstrated an initial improvement in seizure control. Complete tolerance was observed in 9 patients, partial tolerance in 9, and partial tolerance that responded to an increased dose of clobazam in 12. Seventy-two percent of patients reported improvement and 26% worsening in at least one parameter of neurologic function after beginning clobazam. The improvement in neurologic function correlated poorly with change in seizure control. Patients who discontinued 1,4-benzodiazepine (n = 37) had a greater improvement in attention span, alertness, balance, drooling, and mood compared to the remainder of the group. These data suggest that clobazam is effective in the treatment of children with a wide range of epilepsies and seizure types and support the clinical impression that clobazam is associated with less neurotoxicity than the 1,4-benzodiazepines.

Peripheral benzodiazepine receptors in platelets of epileptic patients

Tolerance to the anticonvulsant effect of benzodiazepines is likely to involve changes at the central benzodiazepine-GABA receptor complex. Peripheral benzodiazepine receptors (pBZRs), which can be measured in platelets, may also be involved. Using a binding assay with [3H]-PK 11195 as radioligand, pBZRs were assayed in platelets of patients taking a variety of antiepileptic drugs (AEDs). Comparisons were made with untreated patients. pBZR receptor density (mean +/- s.e. mean) was increased vs controls (8083 +/- 557 fmol mg-1 protein) in the platelets of patients taking a polypharmacy regime including the benzodiazepine clobazam (12661 +/- 1011 fmol mg-1 protein, P < 0.005) and also in those receiving sodium valproate as monotherapy (15003 +/- 1756 fmol mg-1 protein, P < 0.01). The significance of these findings is unclear, but the use of a specific pBZR antagonist may be a promising avenue for investigating the mechanism of BZ tolerance and its prevention.

Anticonvulsant activity of flumazenil in rats during ontogenetic development

The influence of flumazenil on seizures induced by pentylenetetrazol (PTZ) was studied in rats aged 7, 12, 18, 25, and 90 days. Flumazenil in doses of 25, 37.5, and 50 mg/kg IP injected 10 min before PTZ exhibited a dose-dependent anticonvulsant action in all age groups studied. It was more effective against generalized tonic-clonic than against minimal clonic seizures at all developmental stages studied. In the two youngest groups, minimal seizures were elicited only rarely under control conditions. Pretreatment with the two lower doses of flumazenil resulted in an increased incidence of this type of seizure for these two groups. The anticonvulsant activity found in all age groups is in agreement with data from other benzodiazepines and speaks against a pure benzodiazepine-antagonistic action of flumazenil.

Decreased benzodiazepine receptor binding in epileptic El mice: a quantitative autoradiographic study

Benzodiazepine receptors and subtypes were examined in El mice and normal ddY mice with a quantitative autoradiographic technique. Specific [3H]flunitrazepam binding in stimulated El mice, which had experienced repeated convulsions, was significantly lower in the cortex and hippocampus than in ddY mice and unstimulated El mice. In the amygdala, specific [3H]flunitrazepam binding in stimulated El mice was lower than in ddY mice. There was a tendency for the [3H]flunitrazepam binding in these regions in unstimulated El mice to be intermediate between that in stimulated El mice and that in ddY mice, but there was no significant difference between unstimulated El mice and ddY mice. [3H]Flunitrazepam binding displaced by CL218,872 was significantly lower in the cortex of stimulated El mice than in that of the other two groups, and in the hippocampus of stimulated than of unstimulated El mice. These data suggest that the decrease in [3H]flunitrazepam binding in stimulated El mice may be due mainly to that of type 1 receptor and may be the result of repeated convulsions.

Microionophoretic study with milacemide, a glycine precursor, on mammalian central nervous system cells

1. The effect of milacemide, a glycine percursor known to increase gamma-aminobutyric acid (GABA) and glycine content in the brain, and to have anticonvulsant properties, was tested by ionophoresis on 247 neurones situated in the cerebral cortex and in deeper structures of cats and rats anaesthetized with urethane. 2. Virtually all the neurones, either firing spontaneously or exogenously driven by the excitatory amino acids, glutamate, N-methyl-D-aspartate (NMDA), kainate and quisqualate or by acetylcholine, were reversibly depressed in a dose-dependent fashion. The same depressant effect was observed in animals pretreated with the monoamine oxidase B inhibitor (IMAO-B) deprenyl which is known to reduce milacemide metabolism into glycinamide and glycine. Intravenous administration of milacemide (10 to 100 mg kg-1) also depressed the firing induced by glutamate, NMDA and acetylcholine. 3. When compared to GABA, milacemide was a weaker depressant. However, its effect could still be observed in the presence of the reversible GABAA antagonist, SR 95531, and thus milacemide is unlikely to act through GABA receptors. In addition, on cells unaffected by glycine, milacemide also had a depressant effect, and on cells inhibited by glycine, it was still capable of depressing cell firing during reversible blockade by strychnine of the glycine inhibitory action; thus milacemide is unlikely to act through glycine receptors. Simultaneous release of milacemide and GABA or of milacemide and glycine, did not show potentiation of the inhibitory amino acid action. However, the depressant effect of milacemide was additive with that of GABA and glycine. 4. No consistent depression of glutamate-induced firing was obtained by ionophoresis of glycinamide, the first metabolite of milacemide. 5. It is concluded that milacemide by itself is a depressant agent and that its depressant effect does not necessarily require its metabolism into glycine, or its stimulator effect on the production of GABA.

Differential effects of antiepileptic drugs and beta-carbolines on seizures induced by excitatory amino acids

Agonists acting at subtypes of glutamate receptors, N-methyl-D-aspartate, kainate and quisqualate, induce convulsions in rodents. Clonic seizures induced in mice by intracerebral administration of N-methyl-D-aspartate, kainate or quisqualate were used to study the anti- and proconvulsant potential of antiepileptic drugs and beta-carbolines. Systemic administration showed that the benzodiazepines clonazepam and midazolam blocked convulsions induced by kainate and had no effect on seizures triggered by N-methyl-D-aspartate and quisqualate. In contrast, diazepam blocked convulsions induced by either excitatory amino acid, as did valproate. The benzodiazepine receptor agonist beta-carboline ZK 93423 blocked convulsions induced by kainate but had no effect on seizures induced by N-methyl-D-aspartate or quisqualate. The antagonist beta-carboline ZK 93426 did not affect convulsions induced by excitatory amino acids, while the inverse agonists FG 7142 and ethyl-beta-carboline-3-carboxylate increased the sensitivity of mice to kainate. Phenobarbital and 2-chloroadenosine protected mice against seizures induced by quisqualate and kainate, while baclofen was active against convulsions produced by kainate. MK-801 selectively blocked convulsions induced by N-methyl-D-aspartate, and enhanced the susceptibility of mice to seizures triggered by kainate and quisqualate. Ethosuximide increased the susceptibility of mice to N-methyl-D-aspartate and had little or no effect on other types of seizures. Diphenylhydantoin enhanced the convulsant potential of quisqualate. Trimethadione and carbamazepine did not affect convulsions induced by N-methyl-D-aspartate, kainate or quisqualate. Intracerebral administration of midazolam protected mice against seizures induced by kainate. Ethosuximide increased the susceptibility of mice to N-methyl-D-aspartate, while diphenylhydantoin to quisqualate convulsions.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic-pharmacodynamic modelling of the anticonvulsant effect of oxazepam in individual rats

1. The purpose of this investigation was to examine in vivo drug-concentration anticonvulsant effect relationships of oxazepam in individual rats following administration of a single dose. 2. Whole blood concentration vs time profiles of oxazepam were determined following administration of doses of 4, 8 and 12 mg kg-1. The pharmacokinetics could be described by an open 2-compartment pharmacokinetic model. Following 12 mg kg-1 the values (mean +/- s.e., n = 11) of clearance and volume of distribution were 28 +/- 2 ml min-1 kg-1 and 2.6 +/- 0.31 kg-1, respectively, and were not significantly different from the values obtained at the other doses. 3. The anticonvulsant effect was quantitated by a new technique which allows repetitive determination of the convulsive threshold by direct cortical stimulation within one rat. Significant dose-dependent elevations of the seizure threshold were observed. 4. By pharmacokinetic-pharmacodynamic modelling, a log-linear relationship was found between concentration and anticonvulsant effect. Following 12 mg kg-1 the values (mean +/- s.e., n = 11) of the pharmacodynamic parameters slope and minimal effective concentration (Cmin) were 243 +/- 27 microA and 0.11 +/- 0.02 mg l-1, respectively and not significantly different from the values obtained at the other doses. 5. In a repeatability study the pharmacodynamic parameters were determined twice on two different occasions with an interval of two weeks in the same group of 11 rats. The inter-animal variability in the pharmacodynamic parameter slope was 46%, whereas the intra-animal variability was 24 +/- 18%. The value of the minimal effective concentration was in each animal and on each occasion close to zero within the relatively narrow range of 0.01-0.30mgI. 6. The results of this study showed that it is possible to determine in vivo concentration-anticonvulsant effect relationships of oxazepam under non-steady-state conditions in individual rats. The anti-convulsant effect of oxazepam appeared to be a rapidly reversible direct effect and acute tolerance did not develop within the time frame of the experiments.

Animal models of the epilepsies

The study of mechanisms of the epilepsies requires employment of animal models. Choice of a model system depends upon several factors, including the question to be studied, the type of epilepsy to be modelled, familiarity and convenience. Over 50 models are reviewed. Major categories of models are those for simple partial seizures: topical convulsants, acute electrical stimulation, cortically implanted metals, cryogenic injury; for complex partial seizures: kainic acid, tetanus toxin, injections into area tempesta, kindling, rodent hippocampal slice, isolated cell preparations, human neurosurgical tissue; for generalized tonic-clonic seizures: genetically seizure-prone strains of mouse, rat, gerbil, fruitfly and baboon, maximal electroshock seizures, systemic chemical convulsants, metabolic derangements; and for generalized absence seizures: thalamic stimulation, bilateral cortical foci, systemic penicillin, gamma-hydroxy-butyrate, intraventricular opiates, genetic rat models. The lithium-pilocarpine, homocysteine and rapid repetitive stimulation models are most useful in studies of status epilepticus. Key findings learned from each of the models, the model's strengths and weaknesses are detailed. Interpretation of findings from each of these models can be difficult. Do results pertain to the epilepsies or to the particular model under study? How important are species differences? Which clinical seizure type is really being modelled? In a model are behavior or EEG findings only similar superficially to epilepsy, or are the mechanisms comparable? The wealth of preparations available to model the epilepsies underscores the need for unifying themes, and for better understanding of basic mechanisms of the epilepsies.

GABAergic mechanisms in the pathogenesis and treatment of epilepsy

1. Evidence relating to the role of GABA in the pathogenesis of epilepsy is reviewed. 2. Impaired GABAergic function appears to contribute to seizure susceptibility in a variety of genetically-determined syndromes in animals, e.g. genetically epilepsy prone rats showing sound-induced seizures, gerbils with genetically determined epilepsy, and baboons, Papio papio, with photosensitive epilepsy. 3. In epilepsy secondary to a cerebral insult there is some morphological and biochemical evidence for impaired GABAergic function in experimental situations, but little definitive evidence in man. 4. Pharmacological approaches to enhancing GABAergic inhibition include the use of GABA agonists (or prodrugs), GABA-transaminase inhibition, GABA uptake inhibition, and action at the GABA/benzodiazepine allosteric site. 5. Experimental data suggest that the best prospect for potent anticonvulsant action with fewest side effects (myoclonus, sedation, ataxia) is at present offered by GABA-transaminase inhibitors or novel agents acting on the benzodiazepine receptor site.

Anticonvulsant efficacy of clonazepam and the beta-carboline ZK 93423 during chronic treatment in amygdala-kindled rats

Amygdala kindling in rats represents an animal model of partial epilepsy with secondary generalization. Benzodiazepines are active against this type of epilepsy in man but their usefulness is limited by the development of tolerance. This study examined the effects of chronic treatment with the benzodiazepine clonazepam and the beta-carboline ZK 93423 (6-benzyloxy-4-methoxymethyl-beta-carboline-3-carboxylic acid ethyl ester), a full agonist at brain benzodiazepine receptors, on amygdala-kindled seizures in rats. The pharmacokinetics as well as the acute anticonvulsant potency of the drugs were determined prior to the chronic experiments. Based on the data thus obtained clonazepam and ZK 93423 were administered 3 times daily at a dose of 1 or 5 mg/kg i.p., respectively, for 2 weeks. During this treatment period, both compounds significantly reduced seizure severity without indication of tolerance. However, the marked initial effects on seizure duration and/or duration of afterdischarges recorded from the amygdala were attenuated or lost during the 2 weeks of treatment. A pronounced tolerance was also observed with respect to side-effects (sedation, ataxia, muscle relaxation) occurring during treatment. Plasma drug level determinations suggested that the tolerance was of functional nature. The data indicate that, compared to benzodiazepines, the beta-carboline ZK 93423 has no advantage in terms of anticonvulsant potency, side-effects and development of tolerance in the amygdala kindling model of epilepsy.

Midazolam: an effective intravenous agent for seizure control

Midazolam meleate, a water soluble 1,4 benzodiazepine, was used intravenously in 20 patients suffering seizures, of whom 12 were in status epilepticus. In all cases, midazolam in a dose of 2.5-15 mg rapidly terminated the seizure. There were no complications from the use of midazolam. The causes of the seizures were varied but alcohol-withdrawal seizures were the single largest cause. Thirteen patients were taking some form of anticonvulsant medication but only three were in the therapeutic range. Midazolam is seen to be an effective agent in the emergency treatment of seizures.

Bidirectional effects of beta-carbolines in reflex epilepsy

Derivatives of ethyl-beta-carboline-3-carboxylate, ZK 91296, ZK 93423 and ZK 95962 have potent anticonvulsant activity against sound-induced seizures in audiogenic DBA/2 mice and against photically-induced seizures in the baboon, Papio papio. The convulsant beta-carbolines, DMCM and beta-CCM, have proconvulsant and convulsant activity in the same animal models. DMCM and beta-CCM are similar in potency as convulsants in DBA/2 mice (ED50 value for DMCM: 1.3 mg/kg; ED50 value for beta-CCM; 0.8 mg/kg), but differ with respect to their profiles for protection by anticonvulsant drugs. The anticonvulsant potencies of diazepam and clobazam are similar against both types of beta-carboline-induced seizures, whereas quazepam protects better against beta-CCM seizures (4 fold elevation in ED50 value at 1 mg/kg quazepam IP) than against DMCM seizures (1.7 fold elevation in ED50 value), supporting a preferential action of beta-CCM on BZ1 receptors. Valproate (400 mg/kg) and gamma-vinyl-GABA (1.5 g/kg) protect better against beta-CCM seizures (9.5 and 5.9 fold elevations in ED50 values respectively) than against DMCM seizures (1.8 and 2.7 fold elevations in ED50 values respectively). The excitatory amino acid antagonist, 2-amino-7-phosphonoheptanoic acid, has significant anticonvulsant activity against DMCM seizures. The elevated regional GABA levels in brains of DBA/2 mice observed during beta-CCM seizures are eliminated by the pretreatment with Ro 15-1788, which also blocks the seizure activity.