anti-diabetic drugs. introduction according to who, around 100 million of people are patients of...
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ANTI-DIABETIC DRUGS
Introduction
According to WHO, around 100 million of people are patients of diabetes in the world.
Diabetes deaths are likely to increase by more than 50% in the next 10 years without urgent action.
Diabetes will be a primary killer
WHO and IDF indicates that 3.2 million deaths happen for diabetes in each year. In the
world about 6 deaths occur in every minutes for diabetes. Diabetes a primary cause of kidney failure, blindness, and amputations
and so why it said that, in next 25 years diabetes will be the one primary killer.
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Diabetes
Definition from WHO:
-Diabetes mellitus is a metabolic disorder of multiple etiology which is characterized by chronic hyperglycemia with disturbance of carbohydrate, fat and protein metabollism resulting from defects of insulin secretion,
insulin action or both.
Effect of diabetes
long term damage. Dysfunction. Failure of different organ.
Causes
Impaired glucose intake by skeletal muscle. Impaired glycogenesis.
Impaired hepatic output of glucose. Impaired input of glucose.
Symptoms of diabetes
Classical symptoms are-*Thirst*Polyuria*Weight loss*Blurred vision
But in severe form –*Develop ketoacidosis because of fat breaking.*Non ketonic hyperosmolar state will increase. This will lead to coma, if untreated it leads to death.
Classification of Diabetes
Diabetes Mellitus (DM) is classified as –
1) Type-1 Diabetes Mellitus
2) Type-2 Diabetes Mellitus
Type-1 Diabetes Mellitus
Insulin Dependent Diabetes Mellitus or Juvenile Diabetes. It results from pancreatic Beta cell destruction and severe in insulin deficiency. It occurs mostly in Juvenile but occasionally at adults, specially the non-obese.
Type-2 Diabetes Mellitus
Non-Insulin Dependent Diabetes Mellitus, occurs in adult. It is characterized by tissue resistance to the action of insulin combined with a relative deficiency of insulin. Although insulin is produced by Beta cell it is inadequate to overcome the resistance and blood glucose rises.
Some other types
MRDM: Malnutrition Related Diabetes Mellitus.
GDM: Gestational Diabetes Mellitus.
Treatment
Many complications of diabetes can be prevented or delayed through effective management. This includes –
* Healthy diets.
* Physical activity.
* Avoidance of over weights and obesity.
* Not smoking.
Treatment
Diabetes therapy is not only about lowering glucose level but also about the overall complications such as blood pressure and blood lipids. This requires life long care and management.
People with type 2 diabetes often require oral drugs and sometimes insulin is used to control their blood levels.
Treatment
People with type 1 diabetes require insulin to survive.
Insulin
Insulin is a small protein which contains two chains (A and B) linked by disulfide bridges. Insulin is released from pancreatic B cells at a low basal rate and at much higher stimulated rate in response to a variety of stimuli, especially glucose.
Chemistry of insulin
It consists of two open poly-peptide chains (A and B). There are 21 amino acids in chain A and 30 amino acids in B chain. Two chains are inter-linked by a di – sulfide bridge. There is an additional disulfide bridge between the 6th and 11th amino acid residues of the A chain. Breaking the di – sulfide bridge, inactive insulin. It is protein in nature. It’s MW is 5800.
Classification of insulin
1) Short acting* Soluble insulin* Regular insullin* Natural insulin
2) Intermediate acting : * Isophan insuln* Insulin zinc
3) Long acting : * Crystalline insulin
Pharmacokynetics of insulin
Route of administration : Subcuteneous, IV, IM.(orally insulin is digested because it is protein in nature).
Adsorption : slow in subcuteneous. Metabolism : Liver 60%, Kidney 40%. Plasma half life : 3 – 9 minutes. Excretion : Urine.
Hyperglycemia
Hyperglycemia is a condition in which blood sugar increases above the normal level, i.e. above 120mg per 100ml. When the blood sugar level exceeds the renal threshold, sugar appears in the urine. It mainly occurs due to the –
* Impaired glucose intake by skeletal muscle.
*Impaired glycogenesis.
*Impaired hepatic output of glucose.
*Impaired input of glucose.
Hypoglycemia
Hypoglycemia is a condition in which blood sugar decreases below the normal level e. i. below 40mg per 100ml. The symptoms –* Sweating* Anxiety* Dizziness* Headache* Weakness* Fall in blood pressure.
Hypoglycemic agent
Hypoglycemic agents are the agents which used in the treatment and prevention of diabetes mellitus. They are capable of reducing blood sugar level.
Glycosuria
It is the condition when the glucose reuptake by the kidney is impaired. In this condition blood glucose level exceeds 80mg glucose per 100ml of blood.
Classification of Hypoglycemic agents
Hypoglycemic agent
Parenteral Oral
Sulfonyl urea derivatives
Biguinide derivatives
Fast acting(5-12 hours)
Long acting(24-36 hours)
Intermediate acting
(12-24 hours)
Oral Hypoglycaemic Agents
Classification
A) Sulfonylureas
1.First generation sulfonylureas:
- Tolbutamide
- Chlorpropamide
- Acetohexamide
2.Second generation sulfonylureas:
-Glibenclamide
-glipizide
-glicazide
B) Biguanides– Metformine– Phenformine– Buformine
Sulfonyl urea
Chemistry
Sulfonylureas are chemically related with sulfonamide structure.The compounds are aryl-sulfonyl-ureas with substitution on the benzene and urea group.The basic structure is-
R1 SO2 –NH-CO-NH-R2R1 SO2 –NH-CO-NH-R2
SAR of Sulfonylureas
Activity and potency of sulfonylureas change with introducing of new group or substituents to the basic structure of sulfonylureas called SAR of sulfonylureas.
R1 SO2 –NH-CO-NH-R2
R1 R2
Tolbutamide CH3 C4H9
Chlorpropamide Cl C3H7
Acetohexamide CH3
GlyburideCl
OCH3
CONH-(CH2)2
Mechanism of action
The main action of sulfonylureas is to stimulate the Beta cells of islets of langerhans, causing insulin secretion and thus reducing plasma glucose.
High affinity receptors for sulfonylureas are present on the K-ATP channels in Beta cell plasma membrane and the binding of various sulfonylureas parallels their potency in stimulating insulin release.
Sulfonylureas
Bind and decrease K+ entry of Beta cell
Produce depolarisation
Increase Ca+ ion entry
Insulin release from Beta cell
Anti- diabetic action
Pharmacokynetics
Route of administration : Oral. Absorbtion : Absorbed well from the gut with
food. Distribution : 99% protein bound, can cross
placenta. Metabolism : Liver. Excretion : Urine.
Indications : NIDDM (except in overwieght diabetes)
Adverse effects : Hypoglycemia, Hypersensitivity, Nausea, Vomiting, Bone marrow depression, Diarrhoea, abdominal discomfort.
Contraindications
Diabetes in pregnancy. Known allergy to drug. IDDM. After surgery. Severe renal insufficiency and hepatic
failure. Elderly patient with impaired renal function.
Drug interactions
There are some drugs which potentiates the actions of sulfonylureas i. e. increase hypoglycemic activity. They are –* NSAIDs* Alcohol* Coumarin * Antibacterial agents* Antifungal agents
Also there are some drugs which antagonises the action of sulfonylureas i. e. decrease hypoglycemic activity. They are –* Thiazide* Frusemide* Thyroid hormone* Corticosteroids* Oral contraceptives.
Dosage and Administration
Drugs Given dose Maximum effective dose Administration
Tolbutamide 500mg 3000mg with or immediately after food
Tolazamide 100-250mg 1000mg with food
Chlorpropomide 100-200mg 750mg with food
Glyburide 2.5-5mg 20mg with food
Biguanides
Chemistry :
N-C-NH-C-NH2.HCLCH3
CH3
NH NH
N,N-dimethyl imidodi-carbanimidic diamide HCl
Mechanism of action
1. Biguanides Directly stimulate glycolysis in peripheral tissues with increased glucose removal from blood.
2. Reduce blood glucose level by reducing hepatic gluco-neogenesis.
3. Reduce intestinal glucose absorption. 4. Enhancement of insulin receptor binding.
Pharmacokynetics
Route of administration : Oral. Absorption : Small intestine. Metabolism : Does not bound to plasma
protein. Excretion : Excreted unchanged in urine. Plasma half life : About 2 hours.
Indication
IDDM, NIDDM
Obese person with NIDDM not controlled sulfonylureas.
Secondary failure with sulfonylureas.
Adverse effect
GIT upset : Nausea, vomiting, abdominal discomfort, diarrhoea, fatigue, hypoglycemia.
Lactic acidosis (rare but fatal toxic effect).
Cotraindication
Renal insufficiency. Hypoxic condition. Pulmonary insufficiency. Hepatic insufficiency.
Drug interaction
With insulin, does not show any action. With sulfonylureas, show effective action
when a single drug has proved to be ineffective.
Cimetidine increases the absorption of Metformin and decreases the renal clearance.