Pharmacodynamic Drug Interaction of Ethionamide
with Glibenclamide in Normal and Diabetic Rats.
Nitin M.*, Ansari Firdous., Amreen Begum, Syeda Sana
Department of Pharmacology, HKE’s Matoshree Taradevi Rampure Institute of Pharmaceutical Sciences, Sedam Road, Gulbarga-585105, India.
ABSTRACT:
The present study was aimed to find out the
effect of treatment of ethionamide, an antitubercular drug on hypoglycaemic
activity of glibenclamide in normal and diabetic
rats. The study was intended to determine the pharmacodynamic
parameters of drug interaction between glibenclamide
and ethionamide in normal and diabetic rats. The
studies were conducted using six group of normal adult rats of either sex. They
were treated with half therapeutic dose of ethionamide
(0.18 mg/200 g), therapeutic dose of ethionamide
(0.36 mg/200 g), double therapeutic dose of ethionamide
(0.72 mg/200 g), therapeutic dose of glibenclamide
(0.18 mg/200 g) and combination of therapeutic dose of ethionamide
and glibenclamide (0.36 mg/200 g + 0.18 mg/200 g).
Another group of six rats were taken and
diabetes was induced by administering alloxan at a
dose of 100 mg/ kg body weight intraperitoneally.
Rats with glucose levels more than 200 mg/dL were
considered for studied.
The blood samples were collected from tail
vein at predetermined time intervals and blood glucose level was estimated
using GOD/POD method with the aid of ARTOS semi auto analyser.
Ethionamide produced hypoglycaemia
when administered alone. The results indicated that in both normal as well as
in diabetic rats ethionamide treatment altered the hypoglycaemic activity when administerd
along with glibenclamide. This may be due to the
synergistic effect of ethionamide with glibenclamide. The preliminary study indicate the
combination may be unsafe in diabetes associated with tuberculosis.
KEYWORDS:
Glibenclamide, ethionamide, drug interaction, GOD/POD
method, rats.
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 also at a higher risk of tuberculosis (TB) than those
without diabetes.5.
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 characterised 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
noninsulin 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 drug 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 mellitus6.
Patients with diabetes mellitus are also at
a higher risk of tuberculosis. This has been highlighted by several retrospective
and prospective studies. In a study in Mumbai, tuberculosis was found to be the
most complicating illness (5.9%) in a large cohort of over 8000 patients with
diabetes mellitus. In a recent study from the Regional Institute of Medical
Science, Imphal, the prevalence of pulmonary
tuberculosis in diabetes was found to be 27% by radiological diagnosis and 6%
by sputum positive8. A rising prevalence of tuberculosis in diabetes
has been seen with age. Mortality rates in these patients are reported to be
several times higher than in nondiabetic pulmonary
tubercular patients. Although the relative risk of developing pulmonary
tuberculosis and mortality is several times higher in patients with diabetes
mellitus than in matched controls, the clinical symptoms and presentation of
pulmonary tuberculosis are believed to be similar in patient with or without
diabetes mellitus. And so are the bacteriological conversion rates and relapse
rates9. However, those with diabetes mellitus may relapse more often
with resistant strains. In a recently published study from Congo diabetes
appeared to have an induction and aggravating effect on tuberculosis.
Tuberculosis was found to be more pronounced, treatment failures and deaths
were also more frequent10.
It has been observed that a diabetic on ethionamide treatment may have difficulty in the control of
his diabetes. However, as suggested by Conn et
al. (1964) ethionamide may cause disturbance in
carbohydrate metabolism due to anicteric hepatic
damage. Routine liver function tests show hepatic dysfunction in a high
percentage of cases on ethionamide treatment11.
The present study was planned to find out
the effect of ethionamide
on blood glucose levels and on hypoglycaemic activity
of glibenclamide in normal and diabetic rats.
MATERIALS AND METHODS:
Inbred adult albino ras
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. Prior approval was obtained by Institutional
Animal Ethics Committee (IAEC) for conduction of experiments.
Pure samples of glibenclamide
and ethionamide were procured as gift samples from
Sun Pharmaceutical Pvt. Ltd., Mumbai and Macleods
Pharmaceuticals Ltd., Mumbai, respectively. Glucose kit of Span diagnotics Ltd., Surat, was
purchased and used for glucose estimation.
Glibenclamide (100 mg/kg,p.o.)
and ethionamide (200 mg/kg, p.o.)
suspensions were prepared in distilled
water by using 1% w/v gum acacia as a suspending agent and the volume was made upto 100 ml with distilled water.
Inbred adult albino rats of either sex
weighing between 200-250 g 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 16-gauge hypodermic oral feeding needle purchased from
market. The therapeutic dose of drugs administered to animals was calculated
from human dose based on body surface area12.
The albino rats of either sex
weighing 200-250 g were used. Initial blood glucose was estimated in all rats,
by GOD/POD method, to verify the normal blood glucose levels of the animals.
Diabetes was induced with the help of alloxan. Alloxan 100 mg/ml solution in distilled water was prepared.
After 18 h fasting rats were treated 100 mg/kg body weight of alloxan monohydrate by intraperitoneal
route. After injection they were provided with 10% dextrose solution through
feeding bottles. After 3 days, the blood glucose was estimated for verifying
the induction of diabetes. Later, an additional dose of 50 mg/kg body weight
was administered by i.p route if rise of blood
glucose was not seen.
Study in normal and diabetic rats
The rats were fasted for 18 h prior to the
experiment with water ad libitum. During experimentation water was also
withdrawn. The experiment was conducted in six groups,
Group 1: all the six rats treated with
acacia suspension and blood samples were collected at regular intervals. The
blood samples were collected from the tail vein of the rats. The samples were analysed for blood glucose. This stage served as control
without any drug treatment.
Group 2: this group was treated with
therapeutic dose of ethionamide (0.36 mg/200 g body
weight) and blood samples were collected at regular intervals. The samples were
analysed for blood glucose.
Group 3: this group was treated with
therapeutic dose of glibenclamide (0.18 mg/200 g body
weight) and samples were collected at regular time intervals. The samples were analysed for blood glucose.
Table 1: Mean percent glucose reduction in
normal rats treated with glibenclamide, half,
therapeutic and double therapeutic doses of ethionamide
and combination of therapeutic doses of glibenclamide
and ethionamide
|
Group Treatment |
Dosage mg/200g |
Mean percent blood glucose reduction ±
SEM |
||||||
|
Time (h) |
||||||||
|
|
P.O |
1 |
2 |
4 |
6 |
8 |
12 |
24 |
|
Control |
1ml
acacia suspension |
1.47
± 0.19 |
3.97
± 0.17 |
4.76
± 0.19 |
6.18
± 0.17 |
7.19
± 0.15 |
3.90
± 1.55 |
-1.74
±0.24 |
|
Glinemclamide |
0.18 |
3.71
± 0.36 |
22.82
± 0.84 |
29.89
± 1.25 |
38.8
± 0.64 |
25.8
± 0.81 |
12.09
± 0.62 |
-6.18
±0.65 |
|
Ethionamide (TD) |
0.36 |
3.58
± 0.28 |
8.68
± 0.68 |
15.12
± 0.45 |
13.39
± 0.52 |
8.64
± 0.60 |
5.46
± 0.28 |
-3.32
±0.57 |
|
Glibenclamide + Ethionamide |
0.18+
0.36 |
5.46±
0.48 |
23.37±
0.54 |
31.23±
0.52** |
50.65
± 0.93*** |
46.75
±0.65*** |
36.4±0.83** |
2.75
± 0.36 |
|
Ethionamide (HTD) |
0.18 |
6.27
± 0.86 |
14.79
± 0.81 |
20.17
± 0.47 |
17.92
± 0.39 |
15.31
±0.49 |
11.09
± 0.57 |
-5.3
± 1.73 |
|
Ethionamide (DTD) |
0.72 |
2.72
± 0.31 |
17.83
± 0.85 |
25.9
± 0.56 |
21.63
± 0.96 |
14.64
± 1.59 |
12.74
± 0.93 |
-3.19
±0.65 |
n=6; **p<0.01; ***p<0.001
HTD=half therapeutic dose, DTD= double
therapeutic dose; TD= therapeutic dose
p.o.- per oral
Table 2: Mean percent glucose reduction in
diabetic rats treated with glibenclamide, half,
therapeutic and double therapeutic doses of ethionamide
and combination of therapeutic doses of glibenclamide
and ethionamide
|
Group Treatment |
Dosage mg/200g |
Mean percent blood glucose reduction ±
SEM Time (h) |
||||||
|
|
P.O |
1 |
2 |
4 |
6 |
8 |
12 |
24 |
|
Glibenclamide |
0.18 |
4.64
± 0.33 |
22.12
± 0.79 |
31.28
± 0.87 |
38.72
± 1.15 |
22.89
± 0.81 |
11.98
±0.76 |
4.96
± 0.65 |
|
Ethionamide (TD) |
0.36 |
4.99
± 0.31 |
13.46
± 0.47 |
23.5
± 0.73 |
21.5
± 0.72 |
15.64
± 0.52 |
10.32
± 0.91 |
-3.43
± 0.50 |
|
Glibenclamide + Ethionamide |
0.18+
0.36 |
4.69 ±
0.75 |
25.64
± 0.62 |
34.44
± 0.61** |
54.2
± 0.59*** |
40.67
± 0.88*** |
22.6
± 0.38** |
-4.0
± 0.40 |
|
Ethionamide (HTD) |
0.18 |
4.18
± 0.42 |
10.79
± 0.56 |
21.41
± 0.82 |
16.86
± 0.55 |
10.84
± 0.56 |
5.53±
0.45 |
-2.61
± 0.46 |
|
Ethionamide (DTD) |
0.72 |
5.64
± 0.33 |
18.13
± 0.79 |
28.38
± 0.88 |
26.23
± 1.09 |
17.84
± 0.49 |
9.11
± 0.36 |
3.73
± 0.75 |
n=6; **p<0.01; ***p<0.001
HTD= Half Therapeutic Dose; DTD= Double
Therapeutic Dose; TD= Therapeutic Dose
p.o.-per
oral
Group 4: this group was treated with ethionamide (0.36 mg/200 g body weight) followed by glibenclamide (0.18 mg/200 g body weight) after 30 minutes.
The blood samples were collected at regular time intervals.
Group 5:this group was treated with half
therapeutic dose of ethionamide (0.18 mg/200 g body
weight) and blood samples were collected at regular intervals. The samples were
analysed for blood glucose.
Group 6: this group was treated with
double therapeutic dose of ethionamide (0.72 mg/200 g
body weight) and blood samples were collected at regular intervals. The samples
were analysed for blood glucose.
Another group of six rats were taken and
diabetes was induced by administering alloxan at a
dose of 100 mg/ kg body weight intraperitoneally. Rats
with glucose levels more than 200 mg/dL were
considered for studied.
The blood samples were collected into Eppendroff’s tubes containing a small quantity of
anticoagulant (heparin sodium) at regular intervals (0,1,2,4,6,8,12 and 24 h).
The samples were centrifuged and plasma was collected after separation. The
blood glucose was estimated by using glucose kit (GOD/POD method) by semi auto
analyser13.
STATISTICAL
SIGNIFICANCE
The data are presented as mean percent
blood glucose reduction ±SEM. The significance of the observed differences in
percentage reduction in blood glucose levels were calculated by applying
unpaired Student’s t-test. The ‘P’ values <0.05 were considered significant.
RESULTS:
Study conducted in normal rats, the mean
percent blood glucose reduction by ethionamide, glibenclamide, their combination, half therapeutic dose of ethionamide and double therapeutic dose of ethionamide in normal rats are given in Table 1. Ethionamide produced peak hypoglycaemic
activity at 4 h and the percent reduction in glucose was 15.12%. In the control
group there was 4.76% reduction in blood glucose at 4 h. The results indicate
that there was significant effect of ethionamide on
blood glucose levels in normal rats per
se. Glibenclamide produced peak hypoglycaemic activity at 6 h and the percent reduction in
glucose was 38.8%. The combination of glibenclamide
and ethionamide has shown peak hypoglycaemic
activity at 6 h and the percent reduction in glucose was 40.67%. Half
therapeutic and double therapeutic doses of ethionamide
produce hypoglycaemic activity at 4 h and percent
reduction in glucose was 20.17% and 25.90% respectively. The above results
indicate that ethionamide altered the hypoglycaemic activity of glibenclamide.
In case of diabetic rats, the mean
percent blood glucose reduction by therapeutic dose of ethionamide,
half therapeutic dose of ethionamide, double
therapeutic dose of ethionamide, therapeutic dose of glibenclamide and combination of therapeutic doses of ethionamide and glibenclamide are
given in Table 2. Ethionamide produced peak hypoglycaemic activity at 4 h and the percent reduction in
glucose was 23.50%. Glibenclamide produced peak hypoglycaemic activity at 6 h and the percent reduction in
glucose was 38.72%. the combination of glibenclamide
and ethionamide has shown peak hypoglycaemic
activity at 6 h and the percent reduction in glucose was 50.65%. Half
therapeutic and double therapeutic doses of ethionamide
produced hypoglycaemic activity at 4 h and percent redunction in glucose was 21.41% and 28.38% respectively.
The above results indicate that ethionamide altered
the hypoglycaemic activity of glibenclamide.
DISCUSSION:
The mechanism of interaction of a drug can
be established by determining its pharmacodynamic and
pharmacokinetic parameters when administered in presence of another drug. The
pharmacokinetic activity can be established based on 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 rats.
Similarly, the human therapeutic oral dose of ethionamide
ranges from 15-20 mg/day. In the present study, 20 mg of human oral dose was
considered for extending to the rabbits to reveal pharmacodynamic
interaction.
The study on interaction of ethionamide with glibenclamide in
normal and diabetic rats indicate that, ethionamide
altered the blood glucose levels and also altered glibenclamide
induced hypoglycaemia in single dose study. The
growing prevalence of diabetes poses a challenge for TB control as uncontrolled
diabetes leads to a greater risk of developing TB. A recent study showed that
countries that saw an increase in diabetes prevalence also had a significant
increase in the number of people with TB14. People with a weak
immune system as a result of chronic diseases such as diabetes, are at a higher
risk of progressing from latent to active TB. People with diabetes have 2-3
times higher risk of TB compared to people without diabetes. People with
diabetes who are diagnosed with TB have a higher risk of death during TB
treatment and of TB relapse after treatment. WHO- recommended treatments should
be rigorously implemented for people with TB/diabetes15.
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 tuberculosis is more common in
diabetes and as a result the use with antitubercular
drugs alongwith antidiabetic
drugs is also more common.
The pharmacodynamic
data (blood glucose) from blood samples collected after administering drugs to
group of normal rats served as parameter to study the interaction quickly.
Based on this data, experiments were extended in diabetic rats. Literature
survey indicates that ethionamide causes hepatic
damage which leads to disturbance in carbohydrate metabolism. Therefore when ethionamide is given in conjunction with glibenclamide it adds to the hypoglycaemic
action of glibenclamide. Ethionamide
altered the hypoglycaemic activity of glibenclamide when administered alone and when administered
along with glibenclamide in single and multiple dose
study. Animal studies indicate caution, careful monitoring and patient counselling by health care professionals when both ethionamide and glibenclamide are
prescribed together to patients suffering from diabetes and tuberculosis
simultaneously.
CONCLUSION:
Study in normal and diabetic rats indicates
that the interaction of ethionamide with glibenclamide based on pharmacodynamic
response simultaneously produced significant hypoglycaemic
activity.
ACKNOWLEDGEMENT:
Authors are thankful to the authorities of H.K.E.S’s
MTRIPS, Gulbarga for providing facilities to carry out this study. We are
grateful to Sun Pharmaceuticals Ltd., Mumbai and Macleods
Pharmaceuticals Ltd., Mumbai for providing the gift samples of glibenclamide and ethionamide,
respectively.
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Received on 29.04.2013
Modified on 30.05.2013
Accepted on 10.06.2013
© A&V Publication all right
reserved
Research J. Pharmacology and
Pharmacodynamics. 5(4): July–August 2013, 227-231