Effect
of addition of psychotropic drugs to carbamazepine therapy on seizure score
and memory in mice
Ahsan Naqi Rizwan, Atif Ali*, K.K Pillai.
Department
of Pharmacology, Faculty of Pharmacy
Jamia
Hamdard (Hamdard University)
New
Delhi-110062, India.
*Corresponding
author
Atif
Ali
Department
of Pharmacology, Faculty of Pharmacy
Jamia
Hamdard (Hamdard
University)
New
Delhi-110062, India.
Email: aliatif@rediffmail.com
Abstract
Quite
often an epileptic patient suffers from neurobehavioural problems such as
impaired memory, depression, etc., which may have a pathological and/or iatrogenic
basis. Such patients would therefore need additional treatment, beside Antiepileptic
drug (AED) therapy, to correct the accompanying neurological deficits. The
rationale of use of psychotropics along with antiepileptics has been questioned
due to proconvulsant effects of the former. In the present study, the effect
of Carbamazepine (CBZ) on seizure score and memory is evaluated when given
alone and in combination with the antidepressant Sertraline (SERT) and the
benzodiazepine Alprazolam (ALP). Picrotoxin (PTX) induced convulsion model
was used to study the anticonvulsant effect whereas Spontaneous Alternation
Behaviour (SAB) model was used to study the effect on memory. It was observed
that addition of SERT to CBZ or ALP resulted in reduction of anticonvulsant
efficacy of these drugs. However the combination of CBZ + SERT + ALP was superior
as to anti-seizure effect compared to either CBZ or ALP alone. Further, this
combination did not reduce memory performance compared to placebo.
Introduction
Epilepsy is associated with repeated but unpredictable episodes of
loss of consciousness or alteration in behaviour often resulting in embarrassment
and loss of dignity (Robertson et al 1987). Despite a plethora of antiepileptic
medications available, management of epilepsy is a very complex task because
of its association with varied neuropsychiatric disorders (Krishnamoorthy
2001). The most common psychiatric manifestation of epilepsy is depression
(Lambert & Robertson 1999). Neuroscientists were able to explore and understand
the mechanisms that derive seizures and psychopathology. Numerous epidemiology
studies reinforce these goals. In one study it was found that patients with
epilepsy had a four-fold risk of psychiatric disorders in comparison with
random controls (Jalava & Sillanpaa 1996). A review of available studies
suggests that mood (affective) disorders, especially major depression, are
the most common diagnosis in people with epilepsy followed by anxiety, with
the prevalence of major depression ranging from 8 to 48 % and that of anxiety,
5 to 32% (Hermann et al 2000).
Though great attention and concern has been paid to psychosocial function
and quality of life in epilepsy, the assumption that depression is widely
recognized and treated in epileptics is untrue. In fact, depression, along
with other psychiatric disorders of epilepsy remains under-recognized and
under-treated (Weigartz et al 1999; Hermann et al 2000). These psychiatric
comorbidities of epilepsy necessitate the use of psychotropic drugs along
with anticonvulsants. Sertraline (SERT) is a selective serotonin reuptake
inhibitor (SSRI) which is a commonly prescribed antidepressant in epilepsy
patients (Kanner et al 2001). Alprazolam is a
triazolobenzodiazepine derivative, used frequently along with anticonvulsants
to treat anxiety associated with depression in epileptics (Warner 1988).
However, the use of these psychotropic drugs in epileptics has been
cause of concern for clinicians because of reports that these drugs have proconvulsant
or frank convulsant effects (Skowron & Stimel 1992; Rosenstein et al 1993),
since they are known to modulate pre and postsynaptic receptors and neurotransmitters
(GABA, NE, DA, 5-HT etc). Therefore, while considering the use of a second
class of drug, in addition to an AED regimen, for correcting the underlying
psychiatric co-morbidity, it is important to recognize and assess possible
implications of such a combination. Therefore, the present study was undertaken
to evaluate neuropharmacological possibilities with widely prescribed AED,
CBZ in combination with different psychotropic drugs.
Methods
and Aims
Animals
Swiss strain male albino mice (20-26 gm) raised at the Central Animal
House Facility of Jamia Hamdard were used. The animals were housed in polypropylene
cages (10/cage) with a natural light-dark cycle. The mice were fed on a standard
pellet diet (Amrut rat and mice feed, Pune, India) and
water ad libitum.
The project was undertaken with prior approval from the
University Animals Ethics Committee. Utmost care was taken to ensure that
animals were treated in the most humane and ethically acceptable manner.
Drugs and
Chemicals: The studies utilized the following drugs and chemicals
Alprazolam
(ALPRAX; Torrent Pharmaceuticals Ltd., India)
Carbamazepine
(TEGRITAL; Novartis India Ltd.)
Sertraline
(SERTA; Unichem Labs Ltd., India)
Alprazolam
Sertraline combination (ALPRAX Plus; Torrent Pharmaceuticals Ltd., India)
Picrotoxin
(Sigma Chemicals Co. USA)
Scopolamine
(Sigma Chemicals Co. USA)
Piracetam
– (NOOTROPIL; UCB India Ltd.)
Aims
To
study (a) the effect of addition of sertraline and alprazolam to carbamazepine
on chemically induced seizures in mice and (b) the effect of these combinations
on memory scores.
Procedures:
Picrotoxin
induced convulsions
The
method use was essentially similar to that described by Gupta et al (1999).
Male
albino mice were given a dose of picrotoxin i.e. 3.5 mg/kg subcutaneously,
after suitable latency corresponding to the time of peak effect after oral
administration of the test drug. Immediately after administration of picrotoxin,
the animal was placed in the observational area and observed for 30 minutes.
The time of onset of convulsive behavior, nature and severity of convulsions
were carefully recorded using the scoring system 1-7: hyperlocomotion, piloerection
–1; stunning, catatonic posture –2; clonic body tremors –3; prolonged clonic
tremors – 4; tonic forelimb convulsions followed by clonus –5; repetitive
tonic forelimb convulsions followed by clonus –6; tonic extension of both
forelimbs and hindlimbs followed by clonus – 7. A mean cumulative score was
calculated for each treatment group for comparisons and statistical analysis.
The study comprised of eight groups: Gr I: PTX (3.5mg/kg s.c.); Gr
II: ALP (2mg/kg po); Gr III: SERT (10 mg/kg po); Gr IV: ALP + SERT (2 + 10
mg/kg po); Gr V: CBZ (50 mg/kg po); Gr VI: CBZ + SERT (50+ 10 mg/kg po); Gr
VII: CBZ + ALP (50 + 2 mg/kg po); Gr VIII: CBZ + ALP + SERT (50 + 2 + 10 mg/kg
po).
On the day of the experiment the chemoconvulsant was administered at
the interval corresponding to the time of peak effect of the test drug/drugs.
Each animal in a group was observed for a period of 30 minutes for onset,
duration and severity of convulsions
Spontaneous Alternation Behavior on
Plus Maze
The method described by Ragozzino et al (1998) was followed. The assessments
were made in a plus maze made of plywood painted blue/grey. It consisted of
symmetrical arms (23.5 cm long x 8 cm wide) with 10 cm high sidewalls. The
arms extend from a central platform (8 x 8 cm) at a height of 50 cm above
the floor and were labeled A, B, C and D. Mice were placed in the center and
allowed to traverse the maze freely for 6minutes. The number and sequences
of arm entries into different arms were recorded. A 4/5 alternation was defined
as entry into four different arms in overlapping quintuplet sets of five consecutive
arm entries /choices within the total set of arm entries. A B C A C was not
considered an alternation. Using this procedure, possible alteration sequences
are equal to number of arm entries minus four.
The study comprised of ten groups: Gr I: Control (Saline 10ml/kg.);
Gr II: ALP (2mg/kg po); Gr III: SERT (10 mg/kg po); Gr IV: ALP + SERT (2 +
10 mg/kg po); Gr V: CBZ (50 mg/kg po); Gr VI: CBZ + SERT (50+ 10 mg/kg po);
Gr VII: CBZ + ALP (50 + 2 mg/kg po); Gr VIII: CBZ + ALP + SERT (50 + 2 + 10
mg/kg po); Gr IX: Scopolamine (1.5 mg/kg ip); Gr X: Piracetam (250 mg/kg po).
All the treatments were given for 15 days and on the 15th day the
animals in the group were evaluated for Spontaneous Alternation Behavior (SAB).
DOSES
The
doses of the drugs used are based on earlier studies:
|
Drug
|
Dose
|
Ref
|
|
Alprazolam
|
2
mg/kg po
|
(Byrmef
et al 1993)
|
|
Carbamazepine
|
50
mg/kg po
|
(Sluzewska
& Chodera 1992)
|
|
Sertraline
|
10
mg/ kg po
|
(Kelly
& Leonard 1994 )
|
|
Piracetam
|
250
mg/kg po
|
(Christoffersen
et al 1998)
|
|
Scopolamine
|
1.5
mg/kg ip
|
(Sharma
AC and Kulkarni SK 1992)
|
po: per oral; ip: intra peritoneal
Statistical
Analysis
The results are presented as Medians with 25 and 75 percentiles for
seizure score and Mean ± Standard
Error of Mean (SEM) for seizure onset and percent alternation. Data were analyzed
using Kruskal-Wallis one-way analysis of Variance on ranks followed by multiple
comparison tests for seizure score whereas for seizure onset and percent alternation,
one-way analysis of variance (ANOVA) with Dunnet’s ‘t’ test at 95 % confidence
level was employed.
RESULTS
Picrotoxin induced convulsions (Table I)
The
ALP pretreated group showed a moderate decrease in seizure severity and increase
in seizure latency when compared with PTX treated group. SERTR treatment significantly
(p<0.05) increased the severity of convulsions with significant decrease
in onset latency. Whereas the combination of ALP and SERTR, did not affect
the seizure severity and onset latency when compared with PTX treated group.
CBZ
pretreatment significantly (p<0.05) decreased the severity of convulsions
and increased the onset latency to significant extent. Whereas the combination
of CBZ + SERTR increased the seizure severity significantly and the onset
time was decreased to significant extent when compared with CBZ only group.
CBZ
+ ALP combination showed complete protection from PTX induced convulsions.
All phases of convulsions were abolished.
Pretreatment with CBZ + SERTR + ALP combination resulted in a significant
decrease in seizure severity and increase in seizure onset latency (p<0.05)
when compared with both PTX treated and CBZ treated group.
Spontaneous Alternation Behaviour (SAB) (Table
II)
Chronic
administration of ALP resulted in a significant (p<0.05) decrease in memory
scores. SERTR treatment did not affect the SAB.
Co-administration
of ALP + SERTR resulted in a significant decrease in percent alternations
(p<0.05) when compared with saline treated group.
Chronic
administration of CBZ moderately increased the percent alternation. Pretreatment
with CBZ + SERTR did not affect the SAB. Concomitant administration of CBZ
+ ALP significantly decreased the percent alternation when compared both with
saline treated and CBZ only group.
The Scopolamine treated group, taken as negative control, exhibited
significantly lowered percent alternations when compared with saline treated
group.
The
Piracetam treated group, taken as positive control, exhibited significantly
enhanced percent alternations when compared with saline treated group.
Discussion
The
association of psychiatric illness with epilepsy has been the major concern
for the treatment of epilepsy (Reynolds & Trimble 1976). The high incidence
of psychiatric comorbidities seen in epilepsy patients makes it necessary
to treat both disorders (i.e. epilepsy and depression and /or anxiety with
AEDs and psychotropics respectively) at the same time. Therefore the safety
of these drugs in combination should be evaluated in order to optimize the
treatment of epilepsy. With the models
used in our study (Chemoconvulsions) we were able to evaluate whether the
drug/drug combinations raised or lowered seizure threshold. CBZ is a highly
effective conventionally used antiepileptic drug. Our study corroborated earlier
findings (Kubova et al 1993) of CBZ efficacy in attenuating picrotoxin-induced
convulsions. This may be attributed to its mechanism of action i.e. use dependent
sodium channel blockade and weak GABAergic and antiglutamatergic effects (Motohashi
1992).
Sertraline, in the present study led to a significant increase in the
intensity and decrease in latency of picrotoxin induced convulsions. This
shows that SERT lowers seizure thresholds. Our findings are consistent with
earlier observations (Verhoeven 1998; Skowron and Stimmel 1992; Rosenstein
et al 1993) that reported SSRIs to increase seizure frequency and intensity
when co-administered with agents that reduce seizure threshold. The reports
about proconvulsive action of SSRIs are ever increasing, but surprisingly,
these agents are still widely used in epileptics to treat accompanying depression (Kanner et al 2001).
The efficacy of benzodiazepines against chemoconvulsants is well reported
(Mc Namara 1996). Though in our study ALP showed a moderate improvement against
seizures. This effect being attributed
to ALP ability to enhance GABA induced increases in the conductance of chloride.
Comparative
assessment of the drug combinations CBZ+SERTR; CBZ + ALP; and CBZ + ALP +
SERTR revealed that CBZ + ALP is the combination that provided maximal protection
against picrotoxin induced seizures. It was observed that when SERTR was added
to CBZ or to CBZ +ALP, it invariably led to a reduction in the anticonvulsant
efficacy of these drugs. This shows that SERTR could sensitize the convulsant
effect of picrotoxin. This may be attributed to the pharmacological actions
of SERTR. The acute effect of SERTR administration is the increase in 5HT
levels, which may lead to over stimulation of brainstem and spinal cord 5HT1A
and 5HT2 receptors. The symptoms of which are: agitation, myoclonus, hypertension,
possible seizures, in- coordination, rigidity, restlessness, tremor and mental
status/ behavioral changes (Verhoeven 1998; Skowron
and Stimmel 1992).
One
of the neurobehavioral complications associated with epilepsy is memory impairment (Ali et al 2003).
Among different factors contributing to cognitive impairment, adverse effect
of AEDs and psychotropics are frequently reported (Lesser et al 1986). Depression
has also been shown to adversely affect memory and other cognitive functions.
Therefore we evaluated the effects on memory (using spontaneous alternation
behavior model) produced after chronic administration of these drugs/drug
combinations.
In
our study, ALP significantly lowered percent alternations indicating memory
loss that is associated with chronic benzodiazepine therapy (Thompson and
Trimble 1982). This effect of ALP on memory is most
likely due to its GABAergic mechanism.
Sertraline
in the present study did not affect percent alternation indicating no adverse
effects on memory on chronic administration in mice. Both CBZ and SERTR use
in humans has been associated with relatively mild effects on memory and cognition.
In our model when these drugs were given in combination they did not produce
any memory deficit. However, when CBZ was coadministered with Alprazolam it
led to a lowering of percent alternations. This may be due to the fact that
both drugs act as enhancers of the GABAergic system. When ALP was coadministered
with sertraline there was significant decrease in percent alternations suggesting
that the combination adversely affect memory.
The CBZ + ALP + SERTR combination however, did not impair memory as
the percent alternations were almost equal to that of the normal controls.
This combination seems to be superior as far as protection against seizures
and effect on memory is concerned.
Conclusion
The present study assessed the neuropharmacological benefits and complications
associated with psychotropic drugs treatment along with the widely used anticonvulsant,
CBZ. Though the combination of CBZ + ALP exhibited highest anticonvulsant
activity but its deleterious effect on memory is cause of concern.
The combination of CBZ + ALP + SERTR appears to be promising regarding
antiepileptic efficacy with no impairment of memory. However, our results
are preliminary and further studies are warranted to extrapolate animal data
to human situations.
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