Diazepam-atenolol combination antagonizes aminophylline-induced convulsions and lethality in mice

Nebivolol attenuates the anticonvulsant action of carbamazepine and phenobarbital against the maximal electroshock-induced seizures in mice

Background

Due to co-occurrence of seizures and cardiovascular disorders, nebivolol, a widely used selective β₁-blocker with vasodilatory properties, may be co-administered with antiepileptic drugs. Therefore, we wanted to assess interactions between nebivolol and four conventional antiepileptic drugs: carbamazepine, valproate, phenytoin and phenobarbital in the screening model of tonic–clonic convulsions.

Methods

Seizure experiments were conducted in the electroconvulsive threshold and maximal electroshock tests in mice. The chimney test served as a method of assessing motor coordination, whereas long-term memory was evaluated in the computerized step-through passive-avoidance task. To exclude or confirm pharmacokinetic interactions, we measured brain concentrations of antiepileptic drugs using the fluorescence polarization immunoassay.

Results

It was shown that nebivolol applied at doses 0.5–15 mg/kg did not raise the threshold for electroconvulsions. However, nebivolol at the dose of 15 mg/kg reduced the anti-electroshock properties of carbamazepine. The effect of valproate, phenytoin, and phenobarbital remained unchanged by combination with the β-blocker. Nebivolol significantly decreased the brain concentration of valproate, but did not affect concentrations of remaining antiepileptic drugs. Therefore, contribution of pharmacokinetic interactions to the final effect of the nebivolol/carbamazepine combination seems not probable. Nebivolol alone and in combinations with antiepileptic drugs did not impair motor performance in mice. Nebivolol alone did not affect long-term memory of animals, and did not potentiate memory impairment induced by valproate and carbamazepine.

Conclusions

This study indicates that nebivolol attenuated effectiveness of some antiepileptic drugs. In case the results are confirmed in clinical settings, this β-blocker should be used with caution in epileptic patients.

Sotalol enhances the anticonvulsant action of valproate and diphenylhydantoin in the mouse maximal electroshock model

BACKGROUND

Sotalol as a drug blocking β-receptors and potassium KCNH2 channels may interact with different substances that affect seizures. Herein, we present interactions between sotalol and four conventional antiepileptic drugs: carbamazepine, valproate, phenytoin and phenobarbital.

METHODS

Effects of sotalol and antiepileptics alone on seizures were determined in the electroconvulsive threshold test, while interactions between sotalol and antiepileptic drugs were estimated in the maximal electroshock test in mice. Motor coordination and long-term memory were evaluated, respectively, in the chimney test and passive-avoidance task. Brain concentrations of antiepileptics were determined by fluorescence polarization immunoassay.

RESULTS

Sotalol at doses up to 100mg/kg did not affect the electroconvulsive threshold. Applied at doses 60-100mg/kg, sotalol potentiated the antielectroshock action of valproate, while at doses 80-100mg/kg that of phenytoin. Sotalol (up to 100mg/kg) did not affect the action of carbamazepine or phenobarbital in the maximal electroshock. Sotalol alone and in combinations with antiepileptics impaired neither motor performance nor long-term memory in mice. Finally, sotalol did not change brain concentration of valproate and phenytoin, so pharmacokinetic interactions between the drugs are not probable.

CONCLUSIONS

As far as obtained data may be extrapolated into clinical conditions, sotalol may be considered as an arrhythmic drug that does not reduce the action of classical antiepileptic drugs and thereby can be used in epileptic patients with cardiac arrhythmias.

The effect of sympathetic antagonists on the antidepressant action of alprazolam

Alprazolam is an anti-anxiety drug shown to be effective in the treatment of depression. In this study, the effect of sympathetic receptor antagonists on alprazolam-induced antidepressant action was studied using a mouse model of forced swimming behavioral despair. The interaction of three sympathetic receptor antagonists with benzodiazepines, which may impact the clinical use of alprazolam, was also studied. Behavioral despair was examined in six groups of albino mice. Drugs were administered intraperitoneally. The control group received only a single dose of 1% Tween 80. The second group received a single dose of alprazolam, and the third group received an antagonist followed by alprazolam. The fourth group was treated with imipramine, and the fifth group received an antagonist followed by imipramine. The sixth group was treated with a single dose of an antagonist alone (atenolol, a β1-selective adrenoceptor antagonist; propranolol, a non selective β-adrenoceptor antagonist; and prazocin, an α1-adrenoceptor antagonist). Results confirmed the antidepressant action of alprazolam and imipramine. Prazocin treatment alone produced depression, but it significantly potentiated the antidepressant actions of imipramine and alprazolam. Atenolol alone produced an antidepressant effect and potentiated the antidepressant action of alprazolam. Propranolol treatment alone produced depression, and antagonized the effects of alprazolam and imipramine, even producing depression in combined treatments.In conclusion, our results reveal that alprazolam may produce antidepressant effects through the release of noradrenaline, which stimulates β2 receptors to produce an antidepressant action. Imipramine may act by activating β2 receptors by blocking or down-regulating β1 receptors.

Toluene exposure increases aminophylline-induced seizure susceptibility in mice

The effects of toluene on the sensitivity to seizures induced by aminophylline were investigated. Mice were pretreated with an ip injection of corn oil or toluene (100-500 mg/kg) followed by a timed intravenous infusion of aminophylline at various time intervals to assess the seizure thresholds and lethal doses. Toluene increased seizure susceptibility to aminophylline in a dose- and time-dependent manner. Toluene-induced enhancement of seizure susceptibility to aminophylline occurred as early as 30 min and persisted for at least 3 days after a single administration of toluene (500 mg/kg). Treatment of benzaldehyde, one of toluene's metabolites, also showed an increase in the susceptibility to aminophylline. The enhancing effect was also observed in caffeine-induced seizures 1 h, but not 1 day after toluene treatment. These results suggest that individuals with toluene exposure may increase the risk for convulsive and even lethal complications associated with the therapeutic use of aminophylline.

beta-Adrenoceptor blockade enhances the anticonvulsant effect of glutamate receptor antagonists against maximal electroshock

In this study, we evaluated whether beta-adrenoceptor antagonists may modify the protective efficacy of dizocilpine (MK-801), a NMDA receptor antagonist, and 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI 52466), a non-NMDA (AMPA/kainate) receptor antagonist, against maximal electroshock-induced seizures in mice. Propranolol, acebutolol, metoprolol and atenolol were used in doses that did not alter the electroconvulsive threshold. Propranolol potentiated the anticonvulsant activity of MK-801 and GYKI 52466, significantly lowering their ED(50) values from 0.38 and 15.0 to 0.15 (P<0.001) and 8.4 mg/kg (P<0.001), respectively. Similarly, metoprolol lowered the ED(50) of MK-801 and GYKI 52466 from 0.38 and 15.0 to 0.17 (P<0.05) and 11.2 mg/kg (P<0.05). Acebutolol enhanced the protective action of GYKI 52466, lowering its ED(50) value from 15.0 to 12.2 mg/kg (P<0.05), but not that of MK-801. Atenolol, not penetrating the blood-brain barrier, did not affect the anticonvulsive efficacy of MK-801 and GYKI 52466. In conclusion, beta-adrenoceptor antagonists may act synergistically with excitatory amino acid receptor antagonists to inhibit generalised tonic-clonic seizures.

Effects of Saiko-ka-ryukotsu-borei-to, a Japanese Kampo medicine, on tachycardia and central nervous system stimulation induced by theophylline in rats and mice

Effects of Saiko-ka-ryukotsu-borei-to (SRBT) on theophylline-induced tachycardia in anesthetized rats and theophylline-induced locomotion and convulsions in mice were examined. An intraduodenal administration of SRBT (1 g/kg) prevented theophylline (5 mg/kg, i.v.)-induced tachycardia in rats. SRBT also attenuated an increase in arterial blood pressure with a slow reduction in heart rate of rats treated with theophylline, with no influence on the plasma level of theophylline. However, SRBT did not change the beating rate of right atrium isolated from rats in the absence or presence of theophylline or isoproterenol. The locomotor activity of theophylline in mice was reduced by the treatment with SRBT. Furthermore, the latency of convulsions in mice induced by administration of theophylline at a higher dose (240 mg/kg, i.p.) was prolonged by treatment with SRBT (1 g/kg, p.o.) and seven out of fifteen mice were saved from death due to convulsions. These results suggest that theophylline-induced tachycardia and central nervous stimulation are suppressed by SRBT and that SRBT may reduce the undesirable actions of theophylline on the cardiovascular and central nervous systems.

Dose-finding study with nimodipine: a selective central nervous system calcium channel blocker on aminophylline induced seizure models in rats

Nimodipine, a dihydropyridine derivative central nervous system (CNS) selective calcium channel blocker was studied at four different dosage schedules in five different models of seizures in rats. At a dose of 5 mg/kg, i.p. with pretreatment time of 15 min, nimodipine significantly antagonized aminophylline (175 and 200 mg/kg, i.p.), electroshock (150 mA for 0.2 s), pentylenetetrazole (60 and 75 mg/kg, i.p.), aminophylline (100 mg/kg i.p.) + electroshock (66mA for 0.2 s), and aminophylline (100 mg/kg, i.p.) + pentylenetetrazole (40 mg/kg, i.p.) induced seizures in rats. No hemodynamic alteration was observed with this dose of nimodipine. However, 2 mg/kg, i.p. (pretreatment time of 15 min and 30 min) and 5 mg/kg, i.p. (pretreatment time of 30 min) doses of nimodipine failed to demonstrate any significant anticonvulsant effect. The study highlighted the critical role of calcium ion flux into the neurons for the genesis of seizure activity to aminophylline, electroshock, and pentylenetetrazole in rats. Furthermore, the critical dose requirement for nimodipine could be explained on the basis of its short half-life and shorter duration of protection against seizures. Therefore, nimodipine may be tried clinically as an anticonvulsant in patients who are on aminophylline because of bronchial asthma or chronic obstructive pulmonary disease, when such patients have concomitant epilepsy or other seizure prone neurological deficits or are scheduled to undergo electroshock therapy.

A comparative study of aminophylline- and acepifylline-induced seizures and death in the chemoconvulsion model in rats

The convulsive, pro-convulsive and lethal effects of two theophylline-containing bronchodilating agents, aminophylline and acepifylline, have been evaluated in rats. Aminophylline (theophylline ethylenediamine) caused seizures and death in a dose-dependent manner; an intraperitoneal dose of 250 mg kg-1 caused seizures and death in all rats. Intraperitoneal doses of acepifylline (theophylline ethanoate of piperazine) up to 1000 mg kg-1, however, did not cause seizure or death. Further, pre-treatment of the rats by intraperitoneal administration of a subconvulsive dose (100 mg kg-1) of aminophylline caused a significant decrease in CD50 and LD50 values for pentylenetetrazole and a significant increase in the number of positive responders (i.e. rats with a pentylenetetrazole-induced seizure score of 3 or more on a seizure scale ranging from 0 to 6) and death rate compared with those obtained for rats pre-treated with an equivalent intraperitoneal dose (140 mg kg-1) of acepifylline ('equivalent dose' referred to here denotes the theophylline content of the two preparations). The study has established the neurosafety profile of acepifylline and documents a safer alternative to aminophylline for use in asthmatics suffering from concomitant epilepsy or other seizure-prone neurological defects.

Search for an antidote to electroconvulsion and lethality in aminophylline-sensitized mice

Diazepam (10 mg/kg i.p.) or MK-801 (0.25 mg/kg i.p.) offered complete protection against corneal electroshock (30 mA x 0.2 s)-induced tonic seizures and lethality but failed to protect from aminophylline (150 mg/kg i.p.) + electroshock (15 mA x 0.2 s)-induced tonic seizures and lethality in mice. The diazepam (2.5 mg/kg i.p.) and MK-801 (0.25 mg/kg i.p.) combination completely protected the mice from aminophylline + electroshock-induced seizures and lethality. Sodium valproate (500 mg/kg i.p.) protected the mice from electroshock (30 mA) per se and aminophylline + electroshock (15 mA)-induced seizure and lethality. The present study established the neurosensitizing potential of a single, non-convulsive dose of aminophylline for electroconvulsion due to subthreshold intensity electroshock and demonstrated the prophylactic efficacy of sodium valproate and the synergistic therapeutic potential of diazepam and MK-801 combination against such seizure attacks.