THE PHYSIOLOGICAL AND BIOCHEMICAL ACTION OF SOME SELECTED
DRUGS
ANTIHYPERTENSIVE AGENTS
Hypertension is the most common cardiovascular disease. The prevalence varies with age, race,
education, and many other variables. According to some studies, 60–80% of both men and
women will develop hypertension by age 80. Sustained arterial hypertension damages blood
vessels in kidney, heart, and brain and leads to an increased incidence of renal failure, coronary
disease, heart failure, stroke, and dementia. Effective pharmacologic lowering of blood pressure
has been shown to prevent damage to blood vessels and to substantially reduce morbidity and
mortality rates.
The diagnosis of hypertension is based on repeated, reproducible measurements of elevated
blood pressure. Epidemiological studies indicate that the risks of damage to kidney, heart, and
brain are directly related to the extent of blood pressure elevation. The table below shows the
different stages of hypertension.
Classification of hypertension on the basis of blood pressure
Systolic/Diastolic Pressure (mm Hg) Category
< 120/80 Normal
120-129/80 Elevated (Prehypertension)
130-139/80-89 Stage 1 Hypertension
≥ 140/90 Stage 2 Hypertension
≥ 160/100 Stage 3 Hypertension
Positive risk factors for developing hypertension include smoking; metabolic syndrome,
including obesity, dyslipidemia, and diabetes; manifestations of end-organ damage at the time of
diagnosis; and a family history of cardiovascular disease.
A specific cause of hypertension can be established in only 10–15% of patients. Patients in
whom no specific cause of hypertension can be found are said to have essential or primary
hypertension. Patients with a specific etiology are said to have secondary hypertension.
However, in both cases, elevated blood pressure is associated with an overall increase in
, resistance to flow of blood through arterioles, whereas cardiac output is usually normal. No
single factor can be pointed at as the cause of hypertension; thus, it is accepted that elevated
blood pressure is usually caused by a combination of several (multifactorial) abnormalities.
Epidemiologic evidence points to genetic factors, psychological stress, and environmental and
dietary factors (increased salt and decreased potassium or calcium intake) as contributing to the
development of hypertension.
Categories of antihypertensives
In both normal and hypertensive patients, the control of blood pressure occurs at four distinct
anatomical sites namely (1) arterioles (2) postcapillary venules (capacitance vessels) (3) the heart
and (4) the kidney. All antihypertensives act at one or more of this control points and that forms
the basis of their classification. They can be categorized as follows:
1. Diuretics
2. Sympathoplegic agents
3. Direct vasodilators
4. Agents that block production or actions of angiotensin
DIURETICS (Mechanism of action)
Sodium is believed to contribute to vascular resistance by increasing vessel stiffness and neural
reactivity, possibly related to altered sodium-calcium exchange with a resultant increase in
intracellular calcium. These effects are reversed by diuretics or dietary sodium restriction,
Diuretics are agents that lower blood pressure by depleting the body of sodium, as well as
reducing blood volume and cardiac output. Diuretics usually increase the rate of urine flow, and
increase the rate of excretion of Na+ as well as the accompanying Cl-. NaCl in the body is the
major determinant of extracellular fluid volume. Clinically, diuretics are used to reduce
extracellular fluid volume by decreasing total body content of NaCl. Diuretics may also modify
the renal handling of other cations (such as K+, H+, Ca2+, and Mg2+), anions (such as Cl-, HCO3-,
and H2PO4-), and uric acid.
Types of Diuretics
There are different categories of diuretics, which includes:
1. Carbonic anhydrase inhibitors
DRUGS
ANTIHYPERTENSIVE AGENTS
Hypertension is the most common cardiovascular disease. The prevalence varies with age, race,
education, and many other variables. According to some studies, 60–80% of both men and
women will develop hypertension by age 80. Sustained arterial hypertension damages blood
vessels in kidney, heart, and brain and leads to an increased incidence of renal failure, coronary
disease, heart failure, stroke, and dementia. Effective pharmacologic lowering of blood pressure
has been shown to prevent damage to blood vessels and to substantially reduce morbidity and
mortality rates.
The diagnosis of hypertension is based on repeated, reproducible measurements of elevated
blood pressure. Epidemiological studies indicate that the risks of damage to kidney, heart, and
brain are directly related to the extent of blood pressure elevation. The table below shows the
different stages of hypertension.
Classification of hypertension on the basis of blood pressure
Systolic/Diastolic Pressure (mm Hg) Category
< 120/80 Normal
120-129/80 Elevated (Prehypertension)
130-139/80-89 Stage 1 Hypertension
≥ 140/90 Stage 2 Hypertension
≥ 160/100 Stage 3 Hypertension
Positive risk factors for developing hypertension include smoking; metabolic syndrome,
including obesity, dyslipidemia, and diabetes; manifestations of end-organ damage at the time of
diagnosis; and a family history of cardiovascular disease.
A specific cause of hypertension can be established in only 10–15% of patients. Patients in
whom no specific cause of hypertension can be found are said to have essential or primary
hypertension. Patients with a specific etiology are said to have secondary hypertension.
However, in both cases, elevated blood pressure is associated with an overall increase in
, resistance to flow of blood through arterioles, whereas cardiac output is usually normal. No
single factor can be pointed at as the cause of hypertension; thus, it is accepted that elevated
blood pressure is usually caused by a combination of several (multifactorial) abnormalities.
Epidemiologic evidence points to genetic factors, psychological stress, and environmental and
dietary factors (increased salt and decreased potassium or calcium intake) as contributing to the
development of hypertension.
Categories of antihypertensives
In both normal and hypertensive patients, the control of blood pressure occurs at four distinct
anatomical sites namely (1) arterioles (2) postcapillary venules (capacitance vessels) (3) the heart
and (4) the kidney. All antihypertensives act at one or more of this control points and that forms
the basis of their classification. They can be categorized as follows:
1. Diuretics
2. Sympathoplegic agents
3. Direct vasodilators
4. Agents that block production or actions of angiotensin
DIURETICS (Mechanism of action)
Sodium is believed to contribute to vascular resistance by increasing vessel stiffness and neural
reactivity, possibly related to altered sodium-calcium exchange with a resultant increase in
intracellular calcium. These effects are reversed by diuretics or dietary sodium restriction,
Diuretics are agents that lower blood pressure by depleting the body of sodium, as well as
reducing blood volume and cardiac output. Diuretics usually increase the rate of urine flow, and
increase the rate of excretion of Na+ as well as the accompanying Cl-. NaCl in the body is the
major determinant of extracellular fluid volume. Clinically, diuretics are used to reduce
extracellular fluid volume by decreasing total body content of NaCl. Diuretics may also modify
the renal handling of other cations (such as K+, H+, Ca2+, and Mg2+), anions (such as Cl-, HCO3-,
and H2PO4-), and uric acid.
Types of Diuretics
There are different categories of diuretics, which includes:
1. Carbonic anhydrase inhibitors
