Effect of Ramipril on the Pharmacodynamics of Gliclazide in Diabetic Rats.
TE Gopala Krishna Murthy and C Mayuren*
Bapatla College of Pharmacy, Bapatla – 522101, (A.P. ) India.
*Corresponding Author E-mail: -email@example.com
Diabetes mellitus is a chronic metabolic disorder characterized by elevated blood glucose concentration known as hyperglycemia. Diabetes mellitus covers a wide range of heterogeneous disease and involves management of its associated acute and chronic complications, thus there is every possibility of administering other drugs along with the primary anti-diabetic agent which may be the cause for a drug-drug interaction to occur. In the present study the possible pharmacodynamic interaction was studied with ramipril and gliclazide in diabetic rats. Gliclazide was studied at a dose of 7.2 mg/kg body weight in diabetic rats. Ramipril was studied at a dose of 0.90 mg/kg bodyweight in diabeic rats, for the interaction study. The drugs were administered orally and the blood samples were collected before and after administration of drug for a period of 16 h. The serum samples were then subjected to glucose estimation by glucose peroxidase method. The percentage reduction in blood glucose levels were calculated with respect to initial levels. Gliclazide showed a significant reduction of elevated and normoglycemic blood glucose levels. The extent of blood glucose reduction was comparatively increased in the case of combination therapy of ramipil and gliclazide. The study also suggests the necessity to readjust the dose of gliclazide when co-administered with ramipril.
KEY WORDS: Alloxan, Ramipril, Drug interaction, Dynamic interaction, Gliclazide, Hyperglycemia
Diabetes mellitus is the most common endocrine disorder characterized by hyperglycemia, altered metabolism of lipids, carbohydrates, proteins and an increased risk of complications from vascular disease1-4. The management of diabetes mellitus involves utilization of various drugs to save life and alleviate symptoms, secondary aims are to prevent long term diabetic complications and by eliminating various risk factors to increase longevity. During such a therapy there is every possibility of occurrence of drug interactions which may be serious and deleterious to the patients. Most drugs used in the current therapy have the capacity to influence many physiological systems 5. Two drugs concomitantly administered will often affect some of the same systems. Diabetes mellitus may be categorized in to two major types, type 1 and type 2. Type2 Diabetes is the most common form of diabetes. Oral hypoglycemic agents like Sulphonylureas, Biguanides, Alphaglucosidase inhibitors, Meglitinides analogues and Thiazolidediones are useful in the treatment of type 2 diabetes mellitus1.
Hypertension is the most common co-morbid condition present along with diabetes and involves various drug therapies of which Angiotensin converting enzyme inhibitors (ACEIs) are common6. Gliclazide is a second generation sulfonylurea, anti-diabetic agent. It is generally well tolerated, is associated with beneficial effects beyond the reduction of blood glucose7. Ramipril, (ACEI) have been used for years to reduce the rate of diabetic nephropathy progression in patients with type-2 diabetes. In addition, ACEIs enhance insulin sensitivity and therefore benefit patients at high risk of developing type-2 diabetes8. Literature study states that ACEIs has the potency to enhance the pharmacodynamic activity of oral hypoglycemic agents9. Hence the study is planned in such a way to bring out the possible influence of ramipril on the pharmacodynamics of gliclazide on diabetic rats.
MATERIALS AND METHODS:
Drugs and Chemicals:
Gliclazide and ramipril were obtained from Aurobindo Pharmaceuticals, Hyderabad, India respectively. Alloxan monohydrate was obtained from OttoKemi, India. The glucose estimation kits were obtained from Excel diagnostics Pvt. Ltd, Hyderabad, India.
UV Spectrophotometer (Elico), Microcentrifuge (Remi), Micropipettes (Tarsons) and Microcentrifuge tubes (Tarsons) were used from the laboratory.
Adult wistar rats of either sex weighing 150 -260g obtained from the animal house of Bapatla College of Pharmacy (1032/ac/07/CPCSEA); Bapatla, were maintained at a constant temperature of 26 ± 2oC and humidity 30-40% with 12 h light/dark cycle, throughout the experiments. The animals were fed with commercial rat feed and sterile water was given ad libitum. The experimental protocol was approved (IAEC/II/BCOP/07-08) by Institutional Animal Ethics Committee (IAEC) of Bapatla College of Pharmacy; Bapatla and was in accordance with the guidelines of the Committee for the Purpose of Control and Supervision of Experimentation on Animals.
Pharmacodynamic interaction in diabetic rats:
Experimental induction of diabetes:
Experimental diabetes in rats was induced by injecting Alloxan monohydrate intra peritoneally at a dose of 150 mg/kg in ice cold normal saline. After 72 hours, samples were collected from rats by orbital puncture of all surviving rats and the serum was analyzed for glucose levels. Rats with blood glucose levels of 200mg/dL and above were considered as diabetic and selected for the study10-12.
Interaction studies on diabetic rats:
The diabetic rats were randomly divided into three groups of six animals each. All the animals were subjected to fasting for 18 hours prior to experimentation and during the course of time the animals had free access to water. Group I served as control and received distilled water with few drops of 0.1N NaOH. Group II received gliclazide 7.2 mg/kg and after a washout period of one week the animals of group II were used as group III and received ramipril 0.90 mg/kg and gliclazide 7.2 mg/kg. All the drugs were administered orally. The blood samples were collected before and after the administration of the drugs at 0, 1, 2, 3, 4, 6, 8, 10, 12, 16 hours by retro orbital puncture method. The samples were centrifuged and the separated serum was subjected to glucose estimation by glucose peroxidase method13. The percent reduction at each time was calculated with respect to initial levels.
Single dose interaction studies:
In the single dose interaction study after a brief washout period, the animals of group III were fasted for a period of 18 hours with water ad libitum and received ramipril 0.9 mg/kg followed by gliclazide 7.2 mg/kg administration 30 minutes later. The blood samples were collected at predetermined intervals and the serum samples were analyzed for glucose by glucose peroxidase method13.
Multiple dose interaction studies:
The animals of group III were administered with the interacting drug (Ramipril) for the following seven consecutive days. On the 7th day after administration of
drug the animals were fasted for 18 hours and on the 8th day the animals were administered with the last dose of ramipril followed by gliclazide administration. The blood samples were collected as discussed earlier and the serum samples were subjected for glucose estimation.
The data are presented as mean ± S.E.M. The significance of the observed difference in the pharmacodynamic parameters of gliclazide and in combination with other drugs was assessed by student’s paired ‘t’ test. A value of P<0.05 was considered as statistically significant.
Gliclazide at a dose of 0.72 mg/kg was studied in diabetic rats and the percent reduction is shown in Figure-1.In the case of diabetic rats, gliclazide showed a maximum reduction of 40.82 % at 2nd hour and 40.16 % at 8th hour. A single dose interaction was performed in combination with ramipril at a dose 0.90 mg/kg and gliclazide 7.2 mg/kg on diabetic rats. The maximum reduction exhibited by Gliclazide alone was increased by 0.94 % and 2.37 % at 2nd and 8th hour on co-administration with ramipril. Multiple dose interaction study revealed that the maximum reduction of gliclazide was increased by 4.31 % (P<0.01) and 5.74 % (P<0.05) at 2nd and 8th hour. Significant potentiation of percent blood glucose reduction was observed from 2nd to 10th hour in multiple dose interaction study. Statistical treatment of the experimental results showed no significant change in case of single dose interaction whereas significant interaction were observed during multiple dose study when compared with single gliclazide treatment in diabetic rats.
Most of the diabetic patients are likely to suffer with hypertension and hence most often anti-hypertensives are co-administered along with oral anti-diabetic drugs. Frequently prescribed anti-hypertensives belong to the class of Angiotensin converting enzyme inhibitors. Literature survey shows that ACEIs have the potency to increase the insulin sensitivity which adds on an evidence for a probable pharmacodynamic interaction between oral anti-diabetic drugs and ACEIs. The onset of action was observed at first hour and the duration of action was noticed up to 16 hours. The maximum reduction of blood glucose by gliclazide was seen at 2nd and 8th hour in diabetic rats. Gliclazide treatment showed a maximum reduction at 2nd hour, this may be due to the stimulation of initial rapid release of insulin and by the property to increase the sensitivity of pancreatic beta cell to glucose14, 15. Gliclazide also increases the sensitivity of peripheral tissues to insulin and gliclazide is metabolized to several metabolites by hepatic cytochrome P450 3A4 and 2C9 iso enzymes and is eliminated in urine. A part of gliclazide is eliminated through the biliary route, which involves entero-hepatic circulation in rats. The re-absorption of gliclazide eliminated through the biliary route might be responsible for a second peak in its hypoglycemic effect in rats16, 17. This might be the reason for the reduction at 8th hour. The onset and duration of action was not altered in case of single and multiple dose interaction studies carried in diabetic rats. Single dose interaction study showed no significant change when compared to single gliclazide treatment whereas, multiple dose interaction in diabetic rats exhibited significant change and confirmed the presence of potential pharmacodynamic interactions between gliclazide and ramipril. The hypoglycemic activity of gliclazide was found to be increased in the presence of ramipril.It is well known that ACEIs improves the insulin sensitivity. ACEIs have dual effects, suppressing the generation of angiotensin II and suppressing the degradation of kinins. The blood glucose reduction of ramipril may be due to the increased insulin sensitivity and may also be due to skeletal muscle blood flow through vasodilation due to lowered angiotensin II or increased endogenous kinin levels18, 19. Therefore the hypoglycemic activity of ramipril may be attributed to its influence on insulin sensitivity. Hence the present investigation warrants further studies to find out the relevance of this interaction in human beings and to postulate the exact mechanism involved. Therefore the dose of gliclazide must be readjusted when ever it needs to be co-administered with ramipril.
The authors are thankful to the management of Bapatla Educational Society for providing all facilities to conduct this experimental work. The authors are thankful to Aurobindo Pharmaceuticals for providing the gratis samples.
Fig.-1: Percent blood glucose reduction of gliclazide 7.2 mg/kg alone and in combination with ramipril 0.90 mg/kg at single and multiple dose interaction studies in diabetic rats.
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