Research Article

Influence of HMG Co-A inhibitor pitavastatin on pharmacodynamics and pharmacokinetics of pioglitazone in rats and rabbits

Venkata Sunil Kumar M.1*, Ramesh A.1, Padmanabha Reddy Y.2

1Vishnu Institute of Pharmaceutical Education & Research, BVRIT, Narsapur, Medak, Telangana, India

2Raghavendra Institute of Pharmaceutical Education and Research (RIPER), Anantapur, A.P, India

*For correspondence

Venkata Sunil Kumar M,

Vishnu Institute of Pharmaceutical Education & Research, BVRIT, Narsapur, Medak, Telangana, India.

Email: venkatasunilkumar@ gmail.com

 

 

 

 

Received: 10 August 2016

Revised: 07 September 2016

Accepted: 15 September 2016

ABSTRACT

Objective: The study was conducted in rats and rabbits with selected oral doses of Pioglitazone and Pitavastatin their combination to evaluate the safety of Pioglitazone therapy in the presence of Pitavastatin.

Methods: Blood samples were collected from rats/rabbits by retro orbital/marginal ear vein puncture respectively at regular intervals of time. The blood glucose was estimated by GOD/POD method and serum Pioglitazone levels by HPLC method.

Results: Pitavastatin showed to reduced blood glucose levels alone and with combination of Pioglitazone in both normal rats and diabetic rats. The serum Pioglitazone levels were increased significantly and pharmacokinetic parameters like AUC, Cmax, Ka, Cl and increase in the T1/2 of Pioglitazone were not altered significantly in presence of Pitavastatin.

Conclusion: The combination might be safe with respect to its hypoglycemic effect; so the doses of Pioglitazone and Pitavastatin are advised to safe when co administered in a clinical situation.

Keywords: Pioglitazone, Pitavastatin, Blood Glucose

 

Introduction

Diabetes mellitus is a chronic metabolic disorder and is characterized by elevated blood glucose and disturbances in carbohydrate, fat and protein metabolism. It may be due to decrease in the synthesis of insulin (type I) or decrease in the secretion of insulin (type II) from beta cells of islets of Langerhans of pancreas. It requires lifelong treatment with drugs, diet control and exercise.1 The thiazolidinediones (TZDs) are a class of oral antidiabetic drugs that improve metabolic control in patients with type 2 diabetes through the improvement of insulin sensitivity by lowering insulin resistance in muscle and fat.2 The co-occurrence of diabetes in obesity patients is most common. Moreover, chronic use of HMG Co-A reductase inhibitors reported to cause type II diabetes.3

Statins are one of the most widely prescribed groups of drugs in the world. Although statins have been shown to be beneficial in primary and secondary prevention of cardiovascular disease (CVD) in a number of trials, current reports of increased risk of type 2 diabetes with statin use are of concern. Pitavastatin belongs to a group of drugs called HMG CoA reductase inhibitors used to lower cholesterol and triglycerides in the blood. Pitavastatins are potent metabolic inhibitors of 3A4, 2C9 enzymes.4 The pharmacokinetic studies indicate the oral bioavailability of pioglitazone is about 80%, it is metabolized by multiple cytochrome P450 (CYP) isoenzymes, mainly by CYP2C8, CYP3A4 and CYP2C9 to several active and inactive metabolites.5

Hence in the present study focusing on CYP3A4 inhibitors like HMG Co A inhibitors Pitavastatin can be co-administered with a potent thiazolidinedione Pioglitazone to study the drug-drug interactions.

Materials and Methods

Albino rats of either sex obtained from M/s. Mahaveer Enterprises, Hyderabad and albino rabbits of either sex obtained from M/s. Ghosh Enterprises, Kolkata were used in the study. All animals were maintained on pellet diet supplied by M/s. Rayan Biotechnologies Pvt. Ltd., Hyderabad with 12h/12h light/dark cycle and water ad libitum. Animals were fasted for 18 h before the experiment.

Study in normal rats

A group of six albino rats weighing between 250-300 g were administered with 10 mg/kg body weight Pioglitazone, orally. The same group was administered with 0.36 mg/ kg body weight Pitavastatin, orally after a wash out period of one week. The same group was also administered with 0.36 mg/ kg body weight Pitavastatin 30 min prior to 10mg/ kg body weight Pioglitazone, after a further wash out period of 1 week. Blood samples were withdrawn from retro orbital puncture at 0, 1, 2, 3, 4, 6, 8, 10 and 12 h intervals. Blood samples were analyzed for blood glucose levels by GOD/POD method using commercial glucose kits (Span diagnostics).6

Study in diabetic rats

Diabetes was induced by the administration of alloxan monohydrate in two doses 100 mg and 50mg/ kg body weight intraperitoneally for two consecutive days.7 A group of 6 rats with blood glucose levels above 250 mg/dL was selected for the study. The study similar to the one conducted in normal rats was repeated in diabetic group.

Study in normal rabbits

A group of four albino rabbits weighing between 1.38-1.7 kg were used in the study. They were administered with 10 mg/1.5 kg body weight Pioglitazone orally. The same group was administered with 0.28 mg/1.5 kg body weight Pitavastatin given orally after a wash out period of 1 week. The same group was also administered with 0.28 mg/1.5 kg body weight Pitavastatin (single and multiple dose treatment) 30 min prior to 10 mg/1.5 kg weight Pioglitazone was administered. Blood samples were collected at 0, 1, 2, 3, 4, 8, 12, 16 and 24 h intervals by puncturing the marginal ear vein in all experiments. Blood samples were analyzed for blood glucose levels by GOD/POD method using commercial glucose kits and for serum Pioglitazone concentration by HPLC method. The animal experiments were approved by our Institutional Animal Ethics committee and by the Government regulatory body for animal research (Regd. No. 1358/ERe/S/10/CPCSEA).

Results and Discussion

Chronic diabetes mellitus precipitates other disorders in the long run leading to existence of several disorders simultaneously.8 Such situations (existence of simultaneous multiple disorders) demand the use of more than one drug simultaneously known as polypharmacy which may precipitate drug interaction problems. In diabetic condition, maintenance of optimal level of blood glucose is essential since hyperglycaemia and hypoglycaemia are unwanted phenomenon. This is obtained by the use of antidiabetic drugs, proper diet and exercise.9 Pioglitazone is a drug of choice in the type 2 diabetic patients since the situation of anti-diabetic drugs are used in combination therapy for longer period of time, whose safety and efficacy of drugs is in determine.10 Pioglitazone is mainly metabolized in the liver by CYP2C9, CYP 2D6, CYP 3A4 and CYP 1A2 isozymes and is highly protein bound drug bound to proteins about 99%.9 The drugs metabolized by the above enzymes are that inhibit/induce the above enzymes may interact with Pioglitazone when they are coadministered. Some experimental studies support the hypothesis that statins may cause diabetes by altering glucose homeostasis through both impaired insulin secretion and diminished insulin sensitivity.11 The prevalence of T2 DM parallels the increasing prevalence of obesity. Hence there is a possibility of CYP3A4 inhibitors like HMG CoA reductase inhibitors Pitavastatin can be coadministered with a potent thiazolidinedione Pioglitazone.

The oral administration of Pioglitazone produced a dose dependent decrease in blood glucose levels in normal rats. The doses of selected drugs for interaction study were also fixed by extrapolating human therapeutic dose of selected drugs to rats and rabbits basing on body surface area.13

The present study was planned to find out the influence of Pitavastatin on pharmacodynamics of Pioglitazone in rats (rodent) and pharmacodynamics as well as pharmacokinetics of Pioglitazone in rabbits (non rodent). Since rat and rabbit are two dissimilar species, if the interaction occurs in both the species, then there is more probability of its occurrence in humans also. Similarly if absence of interaction is seen in both species, it is assumed to be absent in humans also.

The normal rats were selected for preliminary and quick screening of the drugs and small volumes of blood were collected at regular time intervals for the estimation of blood glucose levels. Dose dependent relationship was observed with 5 mg/kg, 10 mg/Kg, and 20 mg/Kg body weight of Pioglitazone in normal rats. From these three doses 10 mg/Kg of Pioglitazone was selected for interaction study as it produced optimum blood glucose reduction which is about 20-30% (Figure 1). A dose of 10 mg/kg body weight of Pioglitazone produced a steep reduction in blood glucose levels. The effect of Pioglitazone on blood glucose levels was studied in the absence and presence of the Pitavastatin. In normal rats, Pitavastatin when administered alone produced moderate increase in blood glucose level might be because of delayed metabolism of Pioglitazone might be due to Pitavastatin improves hormone sensitivity of lipase, GLUT4, and adiponectin expression in mature adipocytes and suppressed adipocyte hypertrophy and insulin resistance. It effects on insulin sensitivity in an insulin-resistant state.13 There by Pitavastatin enhances the hypoglycemic effect of Pioglitazone (Table 1).

Figure 1: Comparison of percentage blood glucose reduction of Pioglitazone 5 mg/kg, 10mg/kg and 20 mg/kg in normal rats.

Based on the results obtained from the normal rats, the study was extended to alloxan induced diabetic rats to find out the drug interaction in diabetic condition. The selected dose of Pioglitazone (10 mg/kg bd.wt) was found to produce significant antihyperglycemic effect at 2 hr interval in diabetic rats. The activity produced with selected dose of Pioglitazone might be due to its mechanism of action for improving insulin sensitivity.14 The selected dose of Pitavastatin (0.36 mg/kg bd.wt) produced a hyperglycaemic activity with peak activity at 2hr when administered alone and was found to increase the antihyperglycaemic activity of Pioglitazone during 1 hr to 12 hr in combination. Pitavastatin is lipophilic (17%, 2.6 mg) in nature. Glycoalbumin, fasting glucose level and HOMA-IR were significantly lower during pitavastatin treatment. In combination Pitavastatin found to enhance the hypoglycemia produced by Pioglitazone in single dose treatment at 1 hr and 12 hr intervals (Table 2).

Table 1: Comparison of % blood glucose reduction of Pioglitazone 10mg/kg, Pitavastatin (0.36 mg/kg) and their combination in normal rats.

Time (Hrs)

% Blood glucose reduction

 

Pioglitazone (10mg/kg)

Pitavastatin (0.36mg/kg)

Combination

0

0.00±0.00

0.00±0.00ns

0.00±0.00

1

12.57±0.42

12.54±0.58 ns

18.99±0.56***

2

23.70±0.45

18.89±0.65***

29.53±1.27***

3

18.87±0.26

16.13±0.56*

25.29±1.39***

4

15.08±0.53

12.52±0.37 ns

22.12±1.23***

6

11.53±0.65

10.60±0.35 ns

19.35±1.45***

8

7.56±0.52

8.26±0.37 ns

15.77±1.16***

10

4.20±0.68

5.92±0.53 ns

12.82±1.18***

12

1.87±0.45

4.01±0.50 ns

9.47±1.01***

p<0.05*, p<0.01**, p<0.001*** Significance followed by one way ANOVA followed by Dunnet's multiple comparison test when compared with Pioglitazone (10mg/kg) group.

Table 2: Comparison of % blood glucose reduction of Pioglitazone 10mg/kg, Pitavastatin (0.36mg/kg) and their combination in diabetic rats.

Time (Hrs)

% Blood glucose reduction

Pioglitazone (10mg/kg)

Pitavastatin (0.36mg/kg)

Combination

0

0.00±0.00

0.00±0.00 ns

0.00±0.00 ns

1

16.49±1.47

17.94±0.42 ns

24.56±1.06***

2

33.05±1.23

26.20±1.05***

35.41±1.06 ns

3

26.57±1.11

22.18±0.58**

32.29±0.79***

4

21.91±1.56

18.36±0.42 ns

27.49±0.72***

6

19.60±1.66

14.55±0.29***

22.70±0.24 ns

8

15.22±1.43

10.95±0.78**

18.95±0.31*

10

10.85±1.22

7.78±0.56 ns

16.04±0.35***

12

5.63±0.95

3.770.51 ns

13.53±0.60***

p<0.05*, p<0.01**, p<0.001*** Significance followed by one way ANOVA followed by Dunnet's multiple comparison test when compared with Pioglitazone (10mg/kg) group.

Table 3: Comparison of % blood glucose reduction of Pioglitazone 10mg/kg, Pitavastatin, Pitavastatin + Pioglitazone (SD) and Pitavastatin + Pioglitazone (MD).

Time (Hrs)

% Blood glucose reduction

Pioglitazone (10mg/1.5kg) Pitavastatin Pitavastatin + pioglitazone (SD) Pitavastatin + pioglitazone (MD)
0 0.00±0.00 0.00±0.00ns 0.00±0.00 ns 0.00±0.00 ns
1 19.91±0.50 14.74±0.51*** 17.79±1.22 ns 21.26±0.44 ns
2 25.76±0.65 19.18±0.60*** 26.21±0.76 ns 26.46±0.38 ns
3 35.02±0.51 22.75±0.79*** 33.41±0.58 ns 34.53±0.54 ns
4 28.16±1.07 19.34±0.92*** 29.97±0.70 ns 31.31±0.89*
8 20.15±0.49 16.20±0.77*** 26.24±0.61*** 27.08±0.88***
12 16.42±0.41 14.28±0.79 ns 22.12±0.68*** 23.62±1.28***
16 12.66±0.41 11.13±0.64 ns 18.00±0.68*** 19.28±1.19***
24 6.60±0.36 7.48±1.12 ns 13.64±1.11*** 14.92±1.21***

p<0.05*, p<0.01*, p<0.001*** Significance followed by one way ANOVA followed by Dunnet's multiple comparison test when compared with Pioglitazone (10mg/kg) group.

Table 4: Mean Serum insulin (µIU/mL) with mean serum glucose level (mg/dL) in Pioglitazone, Pitavastatin and single and multiple dose treatment Pitavastatin +Pioglitazone.

Groups Time (hrs) Mean serum glucose levels (mg/dL) Serum Insulin (μIU/mL)
Pioglitazone 0.00 96.40±2.68 9.73±1.10
3.00 62.60±1.44 9.98±0.95
Pitavastatin 3.00 73.00±1.76 10.62±0.84
Pitavastatin + Pioglitazone (SD) 3.00 61.40±1.91 11.50±0.76
Pitavastatin + Pioglitazone (MD) 3.00 60.40±2.06 12.15±1.01

Table 5: Pharmacokinetic parameters of Pioglitazone alone and in combination with Pitavastatin in normal rabbits.

Pharmacokinetic parameters Pioglitazone Pitavastatin+Pioglitazone (SD) Pitavastatin+Pioglitazone (MD)
AUC0-24 101.27±0.3246 101.59±1.1938 102.08±0.482
AUC 0-inf 105.36±0.3281 109.75±0.3115 102.3±0.4819
AUMC0-24 800.98±4.7346 970.44±10.79* 928.99±13.266***
AUMC0-inf 935.88±5.7307 1288.2±11.2* 934.27±13.293**
Ke 0.1246±0.0002 0.1015±0.0009 0.1044±0.0006
Ka 1.536±0 1.536±0 1.536±0
T1/2 5.55±0.011 6.876±0.036 6.626±0.0628
Vdss 175670±448.65 227147±1760.6* 209481±2092.8***
Cl 21343±66.336 428113±407648 20375±101.46
Tmax 3±0 3±0 3±0
Cmax 9.604±0.0427 10.42±0.0516 9.738±0.093
MRT 8.878±0.0302 11.732±0.0891 11.008±0.138

p<0.05*, p<0.01**, p<0.001*** Significance followed by one way ANOVA followed by Dunnet's multiple comparison test when compared with Pioglitazone (10mg/kg) group.

In normal rabbits the selected dose of Pitavastatin produced slight decrease in blood glucose levels with peak activity at 3 hr. When administered in combination the single dose treatment with Pitavastatin unaltered hypoglycemic activity of Pioglitazone but the activity was sustained from 3 hr to 24 hr compared to Pioglitazone. Whereas the multiple dose treatment of Pitavastatin did not alter the hypoglycemic activity produced with Pioglitazone (Table 3). The serum insulin levels of Pioglitazone were found to be unaltered with sing dose and multiple dose treatments of Pitavastatin (Table 4). The serum Pioglitazone levels were found to be not changed significantly with single and multiple dose treatment of Pitavastatin (Figure 2). The pharmacokinetic parameters like AUC, AUMC, MRT, Vdss, Cl, T1/2, Tmax and Cmax were not altered significantly with both single and multiple dose treatments of Pitavastatin indicating there is no interaction between Pitavastatin and Pioglitazone (table 5).

Figure 2: The pharmacokinetic profile of Pioglitazone concentration versus time with Pioglitazone formulation alone and its combination with Pitavastatin in normal rabbits.

Hence the present study confirms that there is no combined pharmacodynamic interaction and pharmacokinetic interaction with single and multiple dose treatment of Pitavastatin. So the doses of Pioglitazone and Pitavastatin are advised to safe when coadministered in a clinical situation.

Conclusions

The combinations of Pitavastatin with Pioglitazone are safe in two dissimilar species it can be presumed to be safe in humans also. Health care professionals should prescribe this combination to diabetic patients. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.

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