Pharmacodynamic
Drug Interaction of Imipramine with Glibenclamide in Normal Rabbits.
Nitin M.*, Krunal S., Rooman H., Girish M., Chetan M.
Department
of Pharmacology, H.K.E.S’s College of Pharmacy, Gulbarga- 585 105, Karnataka.
ABSTRACT:
The present study was aimed to find out the
effect of single and multiple dose (9 days) treatment of imipramine, an
antidepressant drug on the hypoglycaemic activity of glibenclamide in normal
rabbits. The study was intended to determine the pharmacodynamic parameters of
drug interaction between glibenclamide and imipramine in normal rabbits. The
single dose studies were conducted using a group of five normal rabbits of
either sex. The dose calculations were based on body surface area as described
by Laurence and Bacharach. The experiment was conducted in four stages. Five
normal rabbits were selected for each stage of experiment. These studies were
conducted in the same group of rabbits after the washout period of the
administered drug (Glibenclamide 0.7 mg/ 1.5 Kg body weight and Imipramine 14
mg/ 1.5 Kg body weight) i.e. after
the complete elimination of the drug. The drugs were administered orally. The blood samples were collected by marginal
ear vein at predetermined time intervals and glucose levels were estimated
using GOD/POD method. Multiple dose study was also conducted by using another
group of five normal rabbits as described above. The results indicated
that single and multiple dose treatment of imipramine an antidepressant drug
altered the hypoglycaemic activity of glibenclamide when administered alone and
along with glibenclamide in normal rabbits. This may be due to the synergistic
effect of imipramine with glibenclamide. The preliminary studies indicate the
combination may be unsafe in diabetes associated with depression.
KEYWORDS: Glibenclamide, Imipramine, Drug
interaction, GOD/POD method.
INTRODUCTION:
Polypharmacy is a common practice in the
clinical management of diseases. Widespread use of multiple-drug therapy has
been severely criticized, in part because such treatment appears to increase
the likelihood of deleterious side effects1. To obtain a desired
therapeutic objective or to treat co-existing diseases many a times it becomes
essential for the concomitant use of several drugs together. Simultaneous use
of several drugs often leads to drug-drug interactions2. Diabetes
mellitus is a metabolic disorder resulting from deficiency of insulin leading
to complications involving many organs. It requires lifelong treatment with
drugs coupled with diet control and exercise3,4. Patients with
diabetes mellitus are at risk for microvascular complications like retinopathy,
nephropathy and neuropathy and macrovascular complications like myocardial
infarction that increase morbidity and mortality5. Diabetes is the
most common endocrine disorder and by the year 2010, it is estimated that more
than 200 million people worldwide will have diabetes and 300 million will
subsequently have the diseases by 20256,7.
Diabetes mellitus may be categorized into
several types but the two major types are type I and type II. Type I diabetes
mellitus, formerly called insulin dependent diabetes mellitus (IDDM) is
characterized by an absolute insulin deficiency that results from an immune
mediated or idiopathic form of beta cell dysfunction. Type II diabetes mellitus
also known as non-insulin dependent diabetes mellitus (NIDDM) may be caused by
insulin resistance and relative insulin deficiency or an insulin secretory
defect from beta cells of islets of Langerhans of pancreas. Insulin is the drug
of choice in type I diabetes mellitus and sulfonylureas are the drugs of choice
in type II diabetes mellitus. Glibenclamide is a second generation oral
hypoglycaemic agent which is widely used for the treatment of type II diabetes
mellitus8. It is reported that glibenclamide is metabolized mainly
in liver by cytochrome P-450 (CYP3A4). In addition, CYP1A1, CYP2C9, CYP2D6 and
CYP2C19 also take part in its metabolism9. The hypoglycaemic effect
of glibenclamide was changed during co-administration with CYP inhibitor
ciprofloxacin.
The history reveals that 71% patients had a
lifetime history of at least one neurological disorder associated with diabetes10.
Depression occurs earlier in life for diabetic patients11. Diabetes
patients have 15-20% higher risk of depression than the general population12,13.
There is a possibility that this percentage is even higher, because depression
is under diagnosed and untreated in many diabetic patients14,15.
Depression may be associated with diabetes and to treat diabetic condition,
sulfonylureas are the widely used class of drugs. Glibenclamide is one of the
commonly prescribed drugs due to its low dose and long duration of action.
Imipramine is one of the drugs of choice in the treatment of depression.
Therefore there is probability for concomitant administration of glibenclamide
with imipramine in patients with diabetes associated with depression. This may
lead to drug-drug interaction problems with altered therapeutic activity.
Literature survey indicates that imipramine
has its effect on blood sugar levels to some extent in some cases, but yet not
clinically relevant12 and both the drugs imipramine and
glibenclamide are metabolised by the same cytochrome P450 enzymes, CYP3A4 and
CYP2D68. Hence there is a possibility of interaction at metabolism
levels of glibenclamide with imipramine.
The present study was planned to find out
the effect of single and multiple dose treatment of imipramine on blood glucose
levels and on hypoglycaemic activity of glibenclamide in normal rabbits. If the
interaction occurs in normal animals, which represents the conditions of actual
use of drugs in humans and to understand the mechanism of drug interaction.
Since rabbits is well established model for preclinical hypoglycaemic activity
and are also official model for bioassay and suitable nonrodent animal model for
ease of collection of sufficient volume of blood sample at regular time
intervals.
MATERIALS AND
METHODS:
Animal:
Inbred adult
albino rabbits of either sex were procured from Central Animal House, M. R.
Medical College, Gulbarga. They were maintained on uniform diet and temperature
with 12 h light and dark cycle housed in well ventilated aluminium cages
individually for acclimatization. Standard animal pellet food procured from
Amrut laboratories, Pranav Agro Industries Ltd., Sangli was provided in adequate
quantity, with drinking water ad libitum.
The experimental protocol (HKE COP/IAEC/14/2009-10) was prior approved by
Institutional Animal Ethics committee (IAEC) of H.K.E.S’s College of Pharmacy,
Gulbarga for conduction of experiments. CPCSEA registration number is 142/1999
CPCSEA.
Drugs:
Pure samples of glibenclamide and
imipramine were procured as gift samples from Sun Pharmaceutical Pvt. Ltd.,
Mumbai and Harika drugs (p) Ltd., Hyderabad, respectively. Glucose kit of
swemed diagnostics, Bangalore, was used for glucose estimation.
Preparation of drug solutions for treatment:
Glibenclamide (100 mg/kg, p.o.) and
imipramine (200 mg/kg, p.o.) suspensions prepared in distilled water by using
1% w/v gum acacia as a suspending agent and the volume was made up to 100 ml
and 20 ml with distilled water, respetively.
Experimental
procedure in normal rabbits:
Inbred adult albino rabbits of either sex
weighing between 2.0-2.5 kg were selected and used for the study. Oral route
was selected for the administration of drugs since the drugs under study are
given generally by oral route in clinical practice. The drugs were administered
orally with the help of an oral gag using a soft rubber catheter of 5 mm
diameter16. The therapeutic dose of drugs administered to animals
was calculated from human dose17.
Single dose study:
The rabbits were fasted for 18 h prior to
the experiment with water ad libitum.
During experimentation water also was withdrawn. The experiment was conducted
in four stages. Stage-I: All the five rabbits treated with potable water, and
blood samples were collected at regular time intervals. The blood samples were
collected from the marginal ear vein of the rabbits. The samples were analyzed
for blood glucose. This stage served as control without any drug treatment.
Stage-II: After 4 days, the same group was treated with therapeutic dose of
imipramine (14 mg/ 1.5 kg body weight) and samples were collected at regular
time intervals. The samples were analyzed for blood glucose. Stage-III: After a
washout period (6 days), the same group was treated with therapeutic dose of
glibenclamide (0.7 mg/ 1.5 kg body weight) and samples were collected at
regular time intervals. The samples were analyzed for blood glucose. Stage- IV:
After a further washout period (4 days), the same group was treated with
imipramine (14 mg/ 1.5 kg body weight) followed by glibenclamide (0.7 mg/ 1.5
kg body weight) after 30 minutes. The blood samples were collected at regular
time intervals. The samples were analyzed for blood glucose.
The blood samples were collected into
eppendorff tubes containing a small quantity of anticoagulant (sodium fluoride
and potassium oxalate, 1:3) at regular time intervals (0, 1, 2, 4, 6, 8, 12, 24
and 48 h). Sodium fluoride was added to prevent in vitro glycolysis in the blood samples collected. The above
samples were centrifuged and plasma was collected after separation. The blood
glucose was estimated by using glucose kit (GOD/POD method) by semi auto
analyzer18.
Multiple dose
study:
For studying the influence of multiple dose
treatment of imipramine, another set of five normal rabbits was selected. The
drugs were administered orally. In this experiment at 1st day after
18 h fast therapeutic dose of imipramine and therapeutic dose of glibenclamide
were administered orally with a gap of 30 min. Later from 2nd day
onwards they were treated daily once with the therapeutic dose of imipramine
for the next eight days with regular feeding. On 9th day after 18 h
fast they were again given with combined treatment with therapeutic dose of
imipramine and glibenclamide with 30 min gap. The blood samples were collected
as described in single dose treatment at the specified intervals and glucose
levels were estimated by GOD/POD method.
STATISTICAL
SIGNIFICANCE:
The data are presented
as mean percent blood glucose change ± SEM. The significance of the observed
differences in percentage reduction in blood glucose levels were calculated by
applying paired Student’s t-test in normal rabbits. The ‘P’ values <0.05
were considered as significant.
RESULTS:
In single dose study, the mean percent
blood glucose reduction by imipramine, glibencamide and their combination in
normal rabbits are given in table. 1 and are represented graphically in fig.1.
Imipramine produced peak hypoglycaemic activity at 8 h and the percentage
reduction in glucose was 30.05%. In the control group there was 10.76%
reduction in blood glucose at 8 h. So, the results indicate that there was
significant effect of imipramine on blood glucose levels in normal rabbits.
Glibenclamide produced peak hypoglycaemic activity at 6 h and the percentage
reduction in glucose was 40.22%. The combination of glibenclamide and
imipramine has shown the peak hypoglycaemic activity at 8 h and the percentage
reduction was found to be 51.35%. The above results indicate that imipramine
altered the hypoglycaemic activity of glibenclamide.
Fig. 1: Mean
percentage blood glucose reduction by imipramine, glibenclamide and their
combination in normal rabbits.
The influences of multiple dose treatment
with imipramine on blood glucose levels and on glibenclamide induced
hypoglycaemia are given in table. 2 and are represented graphically in fig. 2.
At the 1st day, combination treatment given group produced a peak
hypoglycaemic activity at 8 h and the percentage reduction in glucose was
51.88%. Whereas at the 9th day, combination treatment given group
produced a peak hypoglycaemic activity at 8 h and the percentage reduction in
glucose was 53.28%. The above results indicate that similar results were
observed in multiple dose treatment as in single dose treatment.
Fig.
2: Mean percent blood glucose reduction by glibenclamide with single and
multiple dose treatment of imipramine (for 9 days) in normal rabbits.
DISCUSSION:
The mechanism of interaction of a drug can
be established by determining its pharmacodynamic and pharmacokinetic
parameters when administered in the presence of another drug. The
pharmacodynamic activity can be established based on the pharmacological
response of the drugs. The human therapeutic oral dose of glibenclamide ranges
from 5-15 mg/day. In the present study, 10 mg of human dose was considered for
extending to the rabbits. Similarly, the human therapeutic oral dose of
imipramine ranges from 50-200 mg/day. In the present study, 200 mg of human
dose was considered for extending to the rabbits to reveal pharmacodynamic
interaction.
Table. 1: Mean
percentage blood glucose reduction by imipramine, glibenclamide and their
combination in normal rabbits.
|
Group Treatment |
Dosage mg/1.5kg P.O |
Mean percent blood glucose change ± SEM |
||||||||
|
Time(h) |
||||||||||
|
0 |
1 |
2 |
4 |
6 |
8 |
12 |
24 |
48 |
||
|
I
Control |
1ml Distilled
water |
0.0 |
1.88±
0.33 |
3.79±
0.21 |
4.74±
0.22 |
9.29±
0.32 |
10.76±
0.58 |
6.57±
0.47 |
0.74±
0.34 |
-0.37±
0.31 |
|
II
Glibenclamide |
0.7 |
0.0 |
4.22±
0.34 |
22.63±
0.86 |
28.57±
1.21 |
40.22±
1.01 |
24.77±
0.54 |
10.93±
0.71 |
4.10±
0.47 |
2.68±
0.60 |
|
III
Imipramine |
14 |
0.0 |
2.62±
0.48 |
5.14±
0.45 |
13.36±
0.49 |
28.53±
0.64 |
30.05±
0.84 |
12.65±
0.53 |
-1.74±
0.40 |
-2.49±
0.46 |
|
IV
Glibenclamide + Imipramine |
0.7 +
14 |
0.0 |
5.47±
0.55 |
24.66±
0.51* |
33.83±
0.50** |
51.35±
0.73** |
53.13±
0.48*** |
21.50±
0.63*** |
3.87±
0.52* |
1.76±
0.42 |
Number of animals n = 5; Significant at
P*<0.02; Highly Significant at P**<0.01; Very highly significant at
P***<0.001
p.o. - per oral; Dosage expressed as
milligram/1.5kilogram body weight of rabbits; SEM- standard error of the mean;
Time expressed in hour.
Table. 2: Mean percentage blood glucose
reduction by glibenclamide with single and multiple dose treatment of
imipramine (for 9 days) in normal rabbits.
|
Group Treatment |
Dosage mg/1.5kg P.O |
Mean percent blood glucose change ± SEM |
||||||||
|
Time(h) |
||||||||||
|
0 |
1 |
2 |
4 |
6 |
8 |
12 |
24 |
48 |
||
|
Single
dose Glibenclamide
+ Imipramine |
0.7 + 14 |
0.0 |
6.14±
0.66 |
25.82±
0.48 |
34.52±
0.80 |
50.22±
0.67 |
51.88±
0.68 |
23.29±
0.74 |
4.67±
0.58 |
2.24±
0.43 |
|
Multiple
dose Glibenclamide + Imipramine (After
9 days) |
0.7 + 14 |
0.0 |
5.39±
0.46 |
24.94±
0.73 |
35.61±
0.61 |
51.48±
0.79 |
53.28±
0.64 |
28.67±
0.54 |
3.24±
0.49 |
1.81±
0.45 |
Number of animals
n = 5; P is not significant
p.o. - per oral; Dosage expressed as
milligram/1.5kilogram body weight of rabbits; SEM- standard error of the mean;
Time expressed in hour.
The study on the interaction of imipramine
with glibenclamide in normal rabbits indicate that, imipramine altered the
blood glucose levels and also altered glibenclamide induced hypoglycaemia in
single dose study. The interaction studies indicated similar aggravation of
hypoglycaemia in multiple dose study also. The literature survey reported that
both depression and diabetes are known to activate the hypothalamic pituitary
adreno-cortical axis and thus depression may enhance the risk for diabetes
through increased sympatho-adrenal system activity or a dysregulation of the
hypothalamic pituitary axis19. In addition, depression induced
abnormalities in neuroendocrine and neurotransmitter function may also
adversely affect glycemic control in diabetes. These include catecholamine,
cortisol, growth hormone, adrenocorticotropin all of which are increased in
depression20. These interaction studies were statistically significant.
Type II diabetes mellitus is more common
disorder than type I and sulfonylureas are the preferred drugs for its
treatment. Among sulfonylureas glibenclamide was selected as a model drug due
to its low dose and its longer duration of action. Since depression is more
common in diabetes and as a result the use with antidepressant drugs alongwith
antidiabetic drugs is also more common. Depression treatment in diabetes is
important because it improves the quality of life, increases treatment compliance,
and permits patients to achieve better glycaemia control, which may reduce
long-term complications and emergencies. Depending on depression intensity,
pharmacological intervention is obligatory. Antidepressants might also be used
as prophylactic treatment for diabetic patients12,21,22.
For preliminary screening and to understand
mechanism of drug interaction single dose studies were used. The
pharmacodynamic data (blood glucose) from blood samples collected before and
after administering drugs to group of rabbits in single dose study served as
parameter to study the interaction quickly. Based on this data of single dose
study in normal rabbits, the experiments were extended to multiple dose study
for 9 days by using another group of normal rabbits and the data was collected
from this group for 48 h. Literature survey indicates that imipramine involves
the same cytochrome P450 enzymes, CYP3A4 and CYP2D6 which are involved in the
metabolism of gibenclamide leading to higher concentration of glibenclamide in
the blood causing hypoglycaemia. This is due to competition for drug
metabolising enzymes at receptor sites leading to delayed metabolism of
glibenclamide in normal rabbits indicate that, imipramine altered the
hypoglycaemic activity of glibenclamide when administered alone and when
administered along with glibenclamide in single and multiple dose study. The
results need to be confirmed in healthy human volunteers and in diabetic
patients. However animal studies indicate caution, careful monitoring and patient
counselling by health care professionals when both imipramine and glibenclamide
are prescribed together to patients suffering from diabetes and depression
simultaneously.
CONCLUSION:
The single and multiple dose
study indicates that the interaction of imipramine with glibenclamide in normal
rabbits based on phrmacodynamic (blood glucose) response altered the
hypoglycemic activity of glibenclamide. This may be due to the synergistic
effect of imipramine with glibenclamide.
ACKNOWLEDGEMENTS:
Authors are thankful to the authorities of
H.K.E.S’s College of Pharmacy, Gulbarga for providing facilities to carry out
this study. We are grateful to Sun Pharmaceuticals Ltd., Mumbai and Harika
drugs (p) Ltd., Hyderabad for providing the gift samples of glibenclamide and
imipramine, respectively.
REFERENCES:
1.
Shorvon SD, Reynolds EH.
Unnecessary polypharmacy for epilepsy. Br
Med J 1977; 1635-37.
2.
Steel KK, Gertman PM,
Cresienze C, Andersen J. Iatrogenic illness on a general medical service at a
university hospital. N Eng J Med 1981; 34: 638-42.
4. Songer TJ, Zimmet PZ.
Epidemology of type –II diabetes on international perspective, Pharmacometrics
8 (Supl.): 1995; 1-11.
5. Cerveny JD, Leder RD, Weart CW.
Issues surrounding tight glycemic control in people with type 2 diabetes
mellitus. Ann Pharmacother 1998; 32: 896-905.
6. Amos A, McCarty D, Zimmet P. The
rising global burden of diabetes and its complications, estimates and
projections to the year 2010. Diabetic Med 1997; 14: S1-S85.
7.
Zimmet P. Globalization,
coca-colonization and the chronic disease epidemic: can the Doomsday scenario
be averted? J Int Med 2000; 247: 301–10.
8. Rang HP, Dale
MM, Ritter JM, Moore PK. Pharmacology. 5th Ed. Edinburg: Churchill Livingstone;
2003.
9. Zharikova O, Fokina V,
Nanorskaya T, Ravindran S, Hill R, Mattison D. Identification of the major
human hepatic and Placental enzyme responsible for the metabolism of glyburide.
Am J Obstel Gynecol 2007; 197: S111.
10. Lustman PJ, Griffith LS, Clouse RE, Cryer PE. Psychiatric illness
in diabetes mellitus. Relationship to symptoms and glucose control. J Nerv Ment
Dis 1986; 174 (12): 736-42.
11. Lustman PJ, Griffith LS, Clouse RE. Depression in adults with
diabetes: results of 5-year follow-up study. Diabetes Care 1988; 11: 605-12.
12. Gomez R, Huber J, Tombini G, Barros H.M.T. Acute effect of
different antidepressants on glycaemia in diabetic and non-diabetic rats. Braz
J Med Biol Res 2001; 34: 57-64.
13. Lilliker SL. Prevalence of
diabetes in a manic-depressive population. Comparative Psychiatry 1980; 21:
270-75.
14. Lustman PJ, Griffith LS, Gavard
JA, Clouse RE. Depression in adults with diabetes. Diabetes Care 1992; 15:
1631-39.
15. Gavard JA, Lustman PJ, Clouse
RE. Prevalence of depression in adults with diabetes. Diabetes Care 1993; 16:
1167-78.
16.
Ghosh MN. Fundamentals of
experimental pharmacology. 1st Ed. Calcutta: Scientific book agency;
1971.
17. Laurence DR, Bacharach AL.
Evaluation of drug activities and pharmacometrics. London and New York:
Academic press; 1964.
18. Trinder P. Ann ClinBiochem 1964; 6: 24.
19. Akker MV, Schuurman A, Metsemakers J, Buntinx F. Is Depression
related to subsequent Diabetes Mellitus? Acta Psychiatrica Scandinavica 2004;
110: 178-83.
20. Marcus MD, Wing RR, Guare J, Blair EH, Jawad A. Lifetime
prevalence of major depression and its effect on treatment outcome in obese
type II diabetes patients. Diabetes Care 1992; 15: 253-55.
21. Lustman PJ, Griffith LS, Freedland KE, Clouse RE. The course of
major depression in diabetes. General Hospital Psychiatry 1997; 19: 138-43.
22. Lustman PJ, Griffith LS, Freedland KE, Kissel SS, Clouse RE.
Cognitive behaviour therapy for depression in type 2 diabetes mellitus. A
randomized, controlled trial. Annals of Internal Medicine 1998; 129: 613-21.
Received on 17.03.2011
Accepted on 09.04.2011
© A&V Publication all right
reserved
Research J. Pharmacology and
Pharmacodynamics. 3(3): May –June, 2011, 129-133