Acute and chronic treatment with mianserin differentially affects the anticonvulsant activity of conventional antiepileptic drugs in the mouse maximal electroshock model

Comorbid epilepsy and depression—pharmacokinetic and pharmacodynamic drug interactions

Background: Major depressive disorder may be encountered in 17% of patients with epilepsy and in patients with drug-resistant epilepsy its prevalence may reach 30%. This indicates that patients with epilepsy may require antidepressant treatment.

Purpose: Both pharmacodynamic and pharmacokinetic interactions between antiepileptic (antiseizure) and antidepressant drugs have been reviewed. Also, data on the adverse effects of co-administration of antiepileptic with antidepressant drugs have been added. This article was submitted to Neuropharmacology, a section of the journal Frontiers in Pharmacology.

Methods: The review of relevant literature was confined to English-language publications in PUBMED databases. Table data show effects of antidepressants on the seizure susceptibility in experimental animals, results of pharmacodynamic interactions between antiepileptic and antidepressant drugs mainly derived from electroconvulsions in mice, as well as results concerning pharmacokinetic interactions between these drugs in clinical conditions.

Conclusion: Antidepressant drugs may exert differentiated effects upon the convulsive threshold which may differ in their acute and chronic administration. Animal data indicate that chronic administration of antidepressants could reduce (mianserin, trazodone) or potentiate the anticonvulsant activity of some antiepileptics (fluoxetine, reboxetine, venlafaxine). There are also examples of neutral interactions (milnacipran).

How Antidepressant Drugs Affect the Antielectroshock Action of Antiseizure Drugs in Mice: A Critical Review

Depression coexists with epilepsy, worsening its course. Treatment of the two diseases enables the possibility of interactions between antidepressant and antiepileptic drugs. The aim of this review was to analyze such interactions in one animal seizure model-the maximal electroshock (MES) in mice. Although numerous antidepressants showed an anticonvulsant action, mianserin exhibited a proconvulsant effect against electroconvulsions. In most cases, antidepressants potentiated or remained ineffective in relation to the antielectroshock action of classical antiepileptic drugs. However, mianserin and trazodone reduced the action of valproate, phenytoin, and carbamazepine against the MES test. Antiseizure drug effects were potentiated by all groups of antidepressants independently of their mechanisms of action. Therefore, other factors, including brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) modulation, should be considered as the background for the effect of drug combinations.

Sotalol does not interfere with the antielectroshock action of selected second-generation antiepileptic drugs in mice

Background

Due to blocking β-receptors, and potassium KCNH2 channels, sotalol may influence seizure phenomena. In the previous study, we have shown that sotalol potentiated the antielectroshock action of phenytoin and valproate in mice.

Materials and methods

As a continuation of previous experiments, we examined the effect of sotalol on the action of four chosen second-generation antiepileptic drugs (oxcarbazepine, lamotrigine, pregabalin, and topiramate) against the maximal electroshock in mice. Undesired effects were evaluated in the chimney test (motor impairment) and step-through passive-avoidance task (long-term memory deficits). Finally, brain concentrations of antiepileptics were determined by fluorescence polarization immunoassay, while those of sotalol by liquid chromatography–mass spectrometry.

Results

Sotalol at doses of up to 100 mg/kg did not affect the electroconvulsive threshold. Applied at doses of 80–100 mg/kg, sotalol did not affect the antielectroshock action of oxcarbazepine, lamotrigine, pregabalin, or topiramate. Sotalol alone and in combinations with antiepileptics impaired neither motor performance nor long-term memory. Finally, sotalol significantly decreased the brain concentrations of lamotrigine and increased those of oxcarbazepine and topiramate. Pharmacokinetic interactions, however, did not influence the final antielectroshock effects of above-mentioned drug combinations. On the other hand, the brain concentrations of sotalol were not changed by second-generation antiepileptics used in this study.

Conclusion

Sotalol did not reduce the antielectroshock action of four second-generation antiepileptic drugs examined in this study. Therefore, this antidepressant drug should not interfere with antiseizure effects of lamotrigine, oxcarbazepine, pregabalin, and topiramate in patients with epilepsy. To draw final conclusions, our preclinical data should still be confirmed in other experimental models and clinical conditions.

Acute and chronic treatment with moclobemide, a reversible MAO-inhibitor, potentiates the antielectroshock activity of conventional antiepileptic drugs in mice

BACKGROUND

Due to enhancing serotonergic and noradrenergic neurotransmission, moclobemide may influence seizure phenomena. In this study, we examined the effect of both acute and chronic treatment with moclobemide on seizures and the action of first-generation antiepileptic drugs: valproate, carbamazepine, phenobarbital and phenytoin.

METHODS

The effect of moclobemide on seizures was assessed in the electroconvulsive threshold test, while its influence on antiepileptic drugs was estimated in the maximal electroshock test in mice. Undesired effects were evaluated in the chimney test (motor impairment) and step-through passive-avoidance task (long-term memory deficits). Finally, brain concentrations of antiepileptics were determined by fluorescence polarization immunoassay.

RESULTS

Given acutely, moclobemide at 62.5 and 75 mg/kg increased the electroconvulsive threshold. In contrast, chronic treatment with moclobemide up to 75 mg/kg did not influence this parameter. Acute moclobemide applied at subthreshold doses (up to 50 mg/kg) enhanced the antielectroshock effects of carbamazepine, valproate and phenobarbital. Chronic moclobemide (37.5-75 mg/kg) increased the action of all four antiepileptic drugs. All revealed interactions, except these between moclobemide and phenobarbital, seem to have pharmacokinetic nature, because the antidepressant drug, either in acute or in chronic treatment, increased the brain concentrations of respective antiepileptic drugs. In terms of undesired neurotoxic effects, acute and chronic moclobemide, antiepileptic drugs, and their combinations did not produce significant motor or long-term memory impairment.

CONCLUSIONS

Acute and chronic therapy with moclobemide can increase the effectiveness of some antiepileptic drugs against the maximal electroshock test. In mice, this effect was, at least partially, due to pharmacokinetic interactions. So far as the results of experimental studies can be transferred to clinical conditions, moclobemide seems safe for the application in patients with epilepsy and depression. Possibly, in the case of certain antiepileptic drugs combined with moclobemide, their doses should be adjusted downwards.

Interactions of antiepileptic drugs with drugs approved for the treatment of indications other than epilepsy

Introduction: Comorbidities of epilepsy may significantly interfere with its treatment as diseases in the general population are also encountered in epilepsy patients and some of them even more frequently (for instance, depression, anxiety, or heart disease). Obviously, some drugs approved for other than epilepsy indications can modify the anticonvulsant activity of antiepileptics. Areas covered: This review highlights the drug-drug interactions between antiepileptics and aminophylline, some antidepressant, antiarrhythmic (class I-IV), selected antihypertensive drugs and non-barbiturate injectable anesthetics (ketamine, propofol, etomidate, and alphaxalone). The data were reviewed mainly from experimental models of seizures. Whenever possible, clinical data were provided. PUBMED data base was the main search source.Expert opinion: Aminophylline generally reduced the protective activity of antiepileptics, which, to a certain degree, was consistent with scarce clinical data on methylxanthine derivatives and worse seizure control. The only antiarrhythmic with this profile of action was mexiletine when co-administered with VPA. Among antidepressants and non-barbiturate injectable anesthetics, trazodone, mianserin and etomidate or alphaxalone, respectively, negatively affected the anticonvulsant action of some antiepileptic drugs. Clinical data indicate that only amoxapine, bupropion, clomipramine and maprotiline should be used with caution. Possibly, drugs reducing the anticonvulsant potential of antiepileptics should be avoided in epilepsy patients.

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.

Interactions of Mexiletine with Novel Antiepileptic Drugs in the Maximal Electroshock Test in Mice: An Isobolographic Analysis

The aim of the study was to evaluate precisely the type of interactions between mexiletine (an antiarrhythmic drug) and four new generation antiepileptic drugs: lamotrigine, oxcarbazepine, topiramate and pregabalin in the maximal electroshock test in mice (MES). The isobolographic analysis was used to assess the nature of interactions between the tested drugs. Total brain concentrations of antiepileptics were also measured to detect possible pharmacokinetic interactions. The results obtained indicated that the mixture of mexiletine and pregabalin at the fixed ratios of 1:1 and 3:1 led to supra-additive interaction in terms of seizure suppression, while the proportion of 1:3 occurred additive. Synergism was also demonstrated for the combination of mexiletine and topiramate in all three proportions. Combinations of mexiletine with lamotrigine and mexiletine with oxcarbazepine were found to be additive. Adverse-effect profiles of mexiletine, antiepileptics and drug combinations were evaluated in the chimney test (motor coordination) and step-through passive-avoidance task (long-term memory). Mexiletine and drug combinations did not impair long-term memory. Moreover, all combinations of mexiletine with lamotrigine, oxcarbazepine and topiramate had no significant effect on motor coordination. However, the results from the chimney test indicated that pregabalin, administered alone at its ED₅₀ dose from the MES-test, significantly impaired motor performance. Similar adverse effects were observed when mexiletine was co-administered with pregabalin at the fixed-dose ratio combinations of 1:1 and 1:3. However, reduction of pregabalin dose at the fixed ratio of 3:1 seems to prevent significant motor impairment. The results may indicate that mexiletine can be considered as an adjunctive drug in antiepileptic treatment, particularly in patients with concomitant cardiac arrhythmia.

Amiodarone, a multi-channel blocker, enhances anticonvulsive effect of carbamazepine in the mouse maximal electroshock model

Cardiac arrhythmia may occur in the course of epilepsy. Simultaneous therapy of the two diseases might be complicated by drug interactions since antiarrhythmic and antiepileptic agents share some molecular targets. The aim of this study was to evaluate the influence of amiodarone, an antiarrhythmic drug working as a multi-channel blocker, on the protective activity of four classical antiepileptic drugs in the maximal electroshock test in mice. Amiodarone at doses up to 75 mg/kg did not affect the electroconvulsive threshold in mice. Acute amiodarone at the dose of 75 mg/kg significantly potentiated the anticonvulsive effect of carbamazepine, but not that of valproate, phenytoin or phenobarbital in the maximal electroshock-induced seizures in mice. The antiarrhythmic agent and its combinations with antiepileptic drugs did not impair motor performance or long-term memory in mice, except for the combination of amiodarone and phenobarbital. Brain concentrations of antiepileptic drugs were not changed. Despite favourable impact of amiodarone on the anticonvulsive action of carbamazepine in the maximal electroshock, co-administration of the two drugs should be carefully monitored in clinical conditions. Further studies are necessary to evaluate effects of chronic treatment with amiodarone on seizure activity and the action of antiepileptic drugs.

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.

Pharmacokinetic/pharmacodynamic considerations for epilepsy - depression comorbidities

INTRODUCTION

Epilepsy may be frequently associated with psychiatric disorders and its co-existence with depression usually results in the reduced quality of life of patients with epilepsy. Also, the efficacy of antiepileptic treatment in depressed patients with epilepsy may be significantly reduced.

AREAS COVERED

Results of experimental studies indicate that antidepressants co-administered with antiepileptic drugs may either increase their anticonvulsant activity, remain neutral or decrease the protective action of antiepileptic drugs in models of seizures. Apart from purely pharmacodynamic interactions, pharmacokinetic mechanisms have been proven to contribute to the final outcome. We report on clinical data regarding the pharmacokinetic interactions of enzyme-inducing antiepileptic drugs with various antidepressants, whose plasma concentration may be significantly reduced. On the other hand, antidepressants (especially selective serotonin reuptake inhibitors) may influence the metabolism of antiepileptics, in many cases resulting in the elevation of plasma concentration of antiepileptic drugs.

EXPERT OPINION

The preclinical data may provide valuable clues on how to combine these two groups of drugs - antidepressant drugs neutral or potentiating the anticonvulsant action of antiepileptics are recommended in this regard. Avoidance of antidepressants clearly decreasing the convulsive threshold or decreasing the anticonvulsant efficacy of antiepileptic drugs (f.e. bupropion or mianserin) in patients with epilepsy is recommended.

Propafenone enhances the anticonvulsant action of classical antiepileptic drugs in the mouse maximal electroshock model

BACKGROUND

Antiarrhythmic and antiepileptic drugs share some mechanisms of actions. Therefore, possibility of interactions between these in epileptic patients with cardiac arrhythmias is quite considerable. Herein, we attempted to assess interactions between propafenone and four conventional antiepileptic drugs: carbamazepine, valproate, phenytoin and phenobarbital.

METHODS

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

RESULTS

Propafenone up to 50mg/kg did not affect the electroconvulsive threshold, significantly enhancing this parameter at doses of 60-90mg/kg. Applied at its subthreshold doses, propafenone potentiated the antielectroshock action of all four tested classical antiepileptics: carbamazepine, valproate, phenytoin, and phenobarbital. Propafenone alone and in combinations with antiepileptics impaired neither motor performance nor long-term memory in mice. Propafenone did not change brain concentration of phenytoin and phenobarbital; however, it significantly decreased brain levels of carbamazepine and increased those of valproate.

CONCLUSIONS

Propafenone exhibits its own anticonvulsant effect and enhances the action of classical antiepileptic drugs against electrically induced convulsions in mice. Further investigations are required to determine the effect of propafenone on antiepileptic therapy in humans.

Mexiletine and its Interactions with Classical Antiepileptic Drugs: An Isobolographic Analysis

Using the mouse maximal electroshock test, the reference model of tonic-clonic seizures, the aim of the present study was to determine the type of interaction between mexiletine (a class IB antiarrhythmic drug) and classical antiepileptics: valproate, carbamazepine, phenytoin, and phenobarbital. Isobolographic analysis of obtained data indicated antagonistic interactions between mexiletine and valproate (for fixed ratio combinations of 1:1 and 3:1). Additivity was observed between mexiletine and valproate applied in proportion of 1:3 as well as between mexiletine and remaining antiepileptics for the fixed ratios of 1:3, 1:1, and 3:1. Neither motor performance nor long-term memory were impaired by mexiletine or antiepileptic drugs regardless of whether they were administered singly or in combination. Mexiletine did not significantly affected brain concentrations of carbamazepine, phenobarbital or phenytoin. In contrast, the antiarrhythmic drug decreased by 23 % the brain level of valproate. This could be, at least partially, the reason of antagonistic interaction between the two drugs. In conclusion, the observed additivity suggests that mexiletine can be safely applied in epileptic patients treated with carbamazepine, phenytoin or phenobarbital. Because of undesirable pharmacodynamics and pharmacokinetic interactions with valproate, mexiletine should not be used in such combinations.

Reboxetine and its influence on the action of classical antiepileptic drugs in the mouse maximal electroshock model

BACKGROUND

Our previous studies revealed that different classes of antidepressant drugs differently affect seizure phenomena. Continuing our research in this field, in the present study we wanted to investigate the influence of acute and chronic treatment with reboxetine, a selective norepinephrine reuptake inhibitor, on the anticonvulsant action of classical antiepileptic drugs.

METHODS

Experiments were conducted in the model of electroconvulsive threshold and maximal electroshock in mice. Motor coordination was evaluated in the chimney test and long term memory in the step-through passive avoidance task. Brain concentrations of antiepileptic drugs were detected by fluorescence polarization immunoassay.

RESULTS

Acute treatment with reboxetine (8-16 mg/kg) significantly raised the electroconvulsive threshold. In contrast, chronic reboxetine (2-16 mg/kg) did not affect this parameter. Single administration of the antidepressant applied at its subthreshold doses enhanced the action of valproate, carbamazepine and phenobarbital. The antielectroshock effect of phenytoin was also potentiated by acute reboxetine, but only at doses increasing the threshold. Repeated administration of reboxetine (8-12 mg/kg) enhanced the anticonvulsant action of carbamazepine, but not that of three remaining antiepileptic drugs. Neither acute nor chronic reboxetine changed the brain concentrations of valproate, carbamazepine, phenytoin or phenobarbital. Therefore, all revealed interactions seem to be pharmacodynamic. In terms of undesired effects, acute/chronic reboxetine and its combinations with classical antiepileptic drugs did not significantly impair motor performance or long-term memory in mice.

CONCLUSIONS

As far as the obtained data can be extrapolated into clinical conditions, it seems that reboxetine may be safely used in the treatment of depressive disorders in epileptic patients.

Effect of acute and chronic tianeptine on the action of classical antiepileptics in the mouse maximal electroshock model

BACKGROUND

The aim of the study was to analyze the influence of acute and chronic treatment with tianeptine, an antidepressant selectively accelerating presynaptic serotonin reuptake, on the protective activity of classical antiepileptic drugs in the maximal electroshock test in mice.

METHODS

Electroconvulsions were produced by means of an alternating current (50 Hz, 25 mA, 0.2 s) delivered via ear-clip electrodes. Motor impairment and long-term memory deficits in animals were quantified in the chimney test and in the passive-avoidance task, respectively. Brain concentrations of antiepileptic drugs were measured by fluorescence polarization immunoassay.

RESULTS

Acute and chronic treatment with tianeptine (25-50 mg/kg) did not affect the electroconvulsive threshold. Furthermore, tianeptine applied in both acute and chronic protocols enhanced the anticonvulsant action of valproate and carbamazepine, but not that of phenytoin. Neither acute nor chronic tianeptine changed the brain concentrations of valproate, carbamazepine or phenytoin. On the other hand, both single and chronic administration of tianeptine diminished the brain concentration of phenobarbital. In spite of this pharmacokinetic interaction, the antidepressant enhanced the antielectroshock action of phenobarbital. In terms of adverse effects, acute/chronic tianeptine (50 mg/kg) and its combinations with classic antiepileptic drugs did not impair motor performance or long-term memory in mice.

CONCLUSION

The obtained results justify the conclusion that tianeptine may be beneficial in the treatment of depressive disorders in the course of epilepsy.

Effect of acutely and chronically administered venlafaxine on the anticonvulsant action of classical antiepileptic drugs in the mouse maximal electroshock model

The influence of acute and chronic treatments with intraperitoneal venlafaxine, a selective serotonin/norepinephrine reuptake inhibitor, on the anticonvulsant activity of selected antiepileptic drugs was studied in the maximal electroshock test in mice. Venlafaxine (12.5 and 25mg/kg), given either acutely or chronically, significantly increased the electroconvulsive threshold. Moreover, both acute and chronic venlafaxine, applied at the highest subprotective dose of 6.25mg/kg, enhanced the anticonvulsant effect of valproate, without affecting the protective action of carbamazepine, phenobarbital and phenytoin. The antidepressant did not affect brain concentration of valproate, indicating that the interaction between the two drugs seems pharmacodynamic in nature. Despite the lack of effect on the antielectroshock action of the remaining antiepileptics, acute venlafaxine increased the brain concentration of phenobarbital, while chronic venlafaxine reduced the brain level of phenytoin. In terms of adverse effects, acute/chronic venlafaxine and antiepileptic drugs alone, as well as their combinations, did not produce significant motor or long-term memory deficits in mice. Summing up, it seems that venlafaxine may be considered as a safe drug for the clinical use in patients with epilepsy and depressive disorders.

Effect of acute and chronic treatment with milnacipran potentiates the anticonvulsant activity of conventional antiepileptic drugs in the maximal electroshock-induced seizures in mice

RATIONALE

Depression often coexists with epilepsy. Simultaneous therapy of the two diseases may be associated with pharmacodynamic and/or pharmacokinetic interactions between antiepileptic and antidepressant drugs.

OBJECTIVES

The aim of this study was to investigate the influence of acute and chronic treatment with intraperitoneal milnacipran (MLN), a selective serotonin/noradrenaline reuptake inhibitor, on the protective activity of valproate, carbamazepine (CBZ), phenytoin, or phenobarbital (PB) in the maximal electroshock (MES) test in mice.

MATERIALS AND METHODS

Electroconvulsions were produced by an alternating current (50 Hz, 25 mA) delivered via ear-clip electrodes. Motor coordination and long-term memory were evaluated in the chimney test and passive-avoidance task, respectively. Brain concentrations of antiepileptic drugs (AEDs) were assessed by immunofluorescence.

RESULTS

Given acutely, MLN at 10 mg/kg increased the convulsive threshold. Acute MLN applied at the subprotective dose of 5 mg/kg enhanced the anticonvulsant effects of CBZ and PB. Chronic treatment with MLN (5-30 mg/kg once daily for 2 weeks) did not affect either the electroconvulsive threshold or the anticonvulsant action of all studied conventional antiepileptic drugs. Since the antidepressant did not affect brain concentrations of antiepileptics used in the study, the revealed interactions seem to be of pharmacodynamic nature. Moreover, acute and chronic MLN, AEDs, and their combinations did not produce significant motor and long-term memory impairment.

CONCLUSIONS

Acute, but not chronic, treatment with MLN can increase the effectiveness of some AEDs against MES-induced seizures in mice. It seems that MLN may also be considered as a candidate drug for clinical trials in patients with epilepsy and depressive disorders.

Characterization of the anticonvulsant activity of doxepin in various experimental seizure models in mice

In this paper, the anticonvulsant characteristics of doxepin were evaluated in numerous experimental seizure models, including maximal electroshock (MES)-, pentylenetetrazole (PTZ)-, isoniazid (ISO)-, 3-mercaptopropionic acid (3-MP)-, bicuculline (BIC)-, thiosemicarbazide (THIO)-, and strychnine (STR)-induced seizures. In addition, the acute adverse-effect profile of doxepin with respect to impairment of motor coordination was assessed with a mouse rotarod test. The evaluation of the time-course and dose-response relationships for doxepin provided evidence that the peak maximum anticonvulsant activity and acute adverse effects occurred 5 min after intraperitoneal (ip) administration. The results also revealed that doxepin had excellent anticonvulsant activity against maximal electroshock-induced seizures in mice with a median effect value (ED(50)) of 6.6 mg/kg. The assessment of acute adverse effects in the rotarod test revealed that doxepin induced acute neurotoxicity, and its median toxic dose (TD(50)) was 26.4 mg/kg. Additionally, doxepin showed anticonvulsant activity in several chemically-induced seizure models, including ISO, 3-MP, BIC, and THI. Based on this study, we can conclude that the antidepressant drug doxepin may be useful for treatment of depression in patients with epilepsy due to its short time to peak maximum anticonvulsant activity after ip administration (5 min) and remarkable anticonvulsant activity (6.6 mg/kg).