2. Hypoglycemic agents
The drugs which are used to lower blood sugar are
called hypoglycemic agents. They are used to treat
diabetes mellitus. (Latin word mellitus means honey)
Diabetes mellitus is characterized by persistent
hyperglycemia, usually with glucosuria
The lack or deficiency of insulin affects carbohydrate,
protein and lipid metabolism. As a result the different
symptoms (manifestations) observed are
hyperglycemia, glucosuria, ketonaemia, ketonuria,
hyperlipidemia, polyuria, polydipsia (increased thirst)
etc.
3. Diabetes mellitus is divided into following types :
Type 1 : Insulin-dependent diabetes mellitus (IDDM). It
is formerly called as Juvenile - onset as it develops generally in
youth. Insulin is essential to treat this type as patients have
little or no endogenous insulin.
Type 2 : Non-insulin-dependent diabetes mellitus
(NIDDM). It is formerly called as adult-onset or maturity-
onset diabetes as it develops in middle ages or in elderly
patients who are often obese. It is treated by dietary
modification or by use of oral hypoglycaemic agents and in
certain cases by insulin.
Type 3 : Malnutrition related diabetes mellitus (MRDM).
Type 4 Secondary diabetes. It is due to certain parcreatic
disease or certain genetic syndrome or may be drug-induced.
4. •Classification :
• Hypoglycaemic agents may be placed in following
groups :
•1. Hormones : Insulin and its preparation.
•2. Oral hypoglycaemic agents or synthetic hypoglycemic
agents
•(a) Sulphonylureas
•1. First generation:- chlorpropamide, tolbutamide,
Acetohexamide
•2.Second Generation :-
glibenclamide,Glipizide,Glimepiride
•(b) Biguanides e. g. Phenformin, metformin.
C) Meglitinides : Repaglinide, Nateglinide
D) Thiazolidinediones – Rosiglitazone,Pioglitazone
6. •INSULIN :
It is a hormone produced by beta-cells of Islets of Langerhans of
pancreas. It is a polypeptide containing 51 amino acids arranged in
two chains namely A and B having 21 and 30 amino acids
respectively. These two chains are connected by two disulphide
bridges (~S~S-bonds of cysteine)
•Source : Pancreas of pig or ox:
Porcine insulin differs from human insulin in only one amino acid
in 'B' chain. Bovine insulin differs from human insulin in two
amino acids in ‘ A' chain and one amino acid in chain B. Human
insulin is produced either by enzymatic modification of porcine
insulin or by use of DNA recombinant technology in micro-
organisms so that amino acid sequence is identical to that of
human insulin.
7. • Uses : It is used
1. to control diabetes mellitus (which is uncontrollable by diet
alone) or to treat Insulin dependent diabetes mellitus.
2. to regulate carbohydrate metabolism.
3. to treat hyperkalaemia.
4. to treat severe ketoacidosis or diabetic coma
•Insulin exerts following action:-
Decrease blood sugar level
Increase oxidation of glucose
Increase muscle glycogen
Decreased Gluconeogenesis
Decreased ketogenesis
Increase Lipogenesis
Increased protein synthesis
8.
9. Induce glycogen synthesis - When glucose levels are high, insulin induces the
formation of glycogen by the activation of the hexokinase enzyme, which adds a
phosphates group in glucose, thus resulting in a molecule that cannot exit the cell.
At the same time, insulin inhibits the enzyme glucose-6-phosphatase, which
removes the phosphate group. These two enzymes are key for the formation of
glycogen. Also, insulin activates the enzymes phosphofructokinase and glycogen
synthase which are responsible of glycogen synthesis.
Increased potassium uptake – forces cells synthesizing glycogen (a very
spongy, "wet" substance, that increases the content of intracellular water, and its
accompanying K+ ions) [58] to absorb potassium from the extracellular fluids;
lack of insulin inhibits absorption. Insulin's increase in cellular potassium uptake
lowers potassium levels in blood plasma. This possibly occurs via insulin-induced
translocation of the Na+/K+-ATPase to the surface of skeletal muscle
cells.[59][60]
10. •Decreased gluconeogenesis and glycogenolysis – decreases production of glucose from
noncarbohydrate substrates, primarily in the liver (the vast majority of endogenous insulin
arriving at the liver never leaves the liver); increase of insulin causes glucose production by
the liver from assorted substrates.
• Increased lipid synthesis – insulin forces fat cells to take in blood glucose, which is
converted into triglycerides; decrease of insulin causes the reverse.
•Increased esterification of fatty acids – forces adipose tissue to make neutral fats (i.e.,
triglycerides) from fatty acids; decrease of insulin causes the reverse.
•Decreased lipolysis – forces reduction in conversion of fat cell lipid stores into blood
fatty acids and glycerol; decrease of insulin causes the reverse.
• Decreased proteolysis – decreasing the breakdown of protein
• Increased amino acid uptake – forces cells to absorb circulating amino acids; decrease
of insulin inhibits absorption.
•Arterial muscle tone – forces arterial wall muscle to relax, increasing blood flow,
especially in microarteries; decrease of insulin reduces flow by allowing these muscles to
contract.
• Increase in the secretion of hydrochloric acid by parietal cells in the stomach.
•Decreased renal sodium excretion.
11. A. Sulfonylureas
These agents are classified as insulin secretagogues,
because they promote insulin release from the β cells
of the pancreas. The primary drugs used today are
tolbutamide and the secondgeneration derivatives,
glyburide, glipizide, and glimepiride.
Mechanism of action:
1) stimulation of insulin release from the β cells of the
pancreas by blocking the ATP-dependent K+ channels,
resulting in depolarization and Ca2+ influx
2) reduction in hepatic glucose production 3) increase
in peripheral insulin sensitivity.
12. Pharmacokinetics:
Given orally, these drugs bind to serum proteins
Metabolized by the liver
Excreted by the liver or kidney
Tolbutamide has the shortest duration of action
(6-12 hours), whereas the second-generation agents
last about 24 hours
Adverse Effects:
Weight gain
Hyperinsulinemia
Hypoglycemia
13. B. Meglitinide analogs
This class of agents includes repaglinide and nateglinide.
Although they are not sulfonylureas, they have common
actions.
Mechanism of action:
Their action is dependent on functioning pancreatic β cells.
They bind to a distinct site on the sulfonylurea receptor of
ATP-sensitive potassium channels, thereby initiating a
series of reactions culminating in the release of insulin.
However, in contrast to the sulfonylureas, the meglitinides
have a rapid onset and a short duration of action.
They are are categorized as postprandial glucose regulators.
Meglitinides should not be used in combination with
sulfonylureas due to overlapping mechanisms of action.
14. Pharmacokinetics:
These drugs are well absorbed orally after being taken
1 to 30 minutes before meals.
Both meglitinides are metabolized to inactive products
by CYP3A4 in the liver.
Excreted through the bile.
Adverse Effects:
Incidence of hypoglycemia is lower than that of the
sulfonylureas.
Weight gain is less of a problem with the meglitinides
than with the sulfonylureas.
15. Biguanides
Metformin (glucophage), the only currently available
biguanide
it increases glucose uptake and utilization by target
tissues, thereby decreasing insulin resistance.
Mechanism of action:
reduction of hepatic glucose output, largely by inhibiting
hepatic gluconeogenesis.
Slowing intestinal absorption of sugars
Improves peripheral glucose uptake and utilization.
Metformin may be used alone or in combination with one
of the other agents, as well as with insulin.
Hypoglycemia has occurred when metformin was taken in
combination.
16. Pharmacokinetics:
Metformin is well absorbed orally, is not bound to serum
proteins
It is not metabolized
Excretion is via the urine.
Adverse effects:
Contraindicated in diabetics with renal and/or hepatic
disease, acute myocardial infarction, severe infection, or
diabetic ketoacidosis.
It should be used with caution in patients greater than 80
years of age or in those with a history of congestive heart
failure or alcohol abuse.
Long-term use may interfere with vitamin B12 absorption.
17. Thiazolidinediones
Troglitazone was the first of these to be approved for the
treatment of Type 2 diabetic, but was withdrawn after a
number of deaths due to hepatotoxicity were reported.
Presently, two members of this class are available,
pioglitazone and rosiglitazone.
Mechanism of action:
Exact mechanism by which the TZDs lower insulin
resistance remains to be elucidated
They are known to target the peroxisome proliferator-
activated receptor-γ (PPARγ)-α nuclear hormone receptor.
Ligands for PPARγ regulate adipocyte production and
secretion of fatty acids as well as glucose metabolism,
resulting in increased insulin sensitivity in adipose tissue,
liver, and skeletal muscle.
18. Pharmacokinetics:
Both pioglitazone and rosiglitazone are absorbed very
well after oral administration and are extensively bound to
serum albumin.
Both undergo extensive metabolism by different
cytochrome P450 isozymes.
Pioglitazone:
Renal elimination is negligible, with the majority of the
active drug and metabolites excreted in the bile and
eliminated in the feces.
Rosiglitazone:
The metabolites are primarily excreted in the urine.
19. α-glucosidase inhibitors
Alpha-glucosidase inhibitors are oral antidiabetic drugs used for diabetes mellitus type 2
that work by preventing the digestion of carbohydrates (such as starch and table sugar).
Acarbose and miglitol are orally active drugs used for the treatment of patients with
Type 2 diabetes.
Mechanism of action:
These drugs are taken at the beginning of meals. They
act by delaying the digestion of carbohydrates, thereby
resulting in lower postprandial glucose levels. Both drugs
exert their effects by reversibly inhibiting membranebound
α-glucosidase in the intestinal brush border. This
enzyme is responsible for the hydrolysis of
oligosaccharides to glucose and other sugars.
Consequently, the postprandial rise of blood glucose is
blunted. Unlike the other oral hypoglycemic agents, these
drugs do not stimulate insulin release, nor do they
increase insulin action in target tissues. Thus, as
monotherapy, they do not cause hypoglycemia.
However, when used in combination with the
sulfonylureas or with insulin, hypoglycemia may develop.
20. Dipeptidyl peptidase-4
inhibitor
DPP-4 inhibitors or gliptins, are a class of oral
hypoglycemics that block DPP-4. They can be used to treat
diabetes mellitus type 2.
The first agent of the class - sitagliptin – was approved by
the FDA in 2006.
Mechanism of action:
Sitagliptin inhibits the enzyme DPP-4, which is responsible
for the inactivation of incretin hormones, such as
glucagon-like peptide-1 (GLP-1). Prolonging the activity of
incretin hormones results in increased insulin release in
response to meals and a reduction in inappropriate
secretion of glucagon.
