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and adrenoceptor blockers and Diuretics

Learning objectives:

1. Regulation of blood pressure by autonomic nervous

system and renin-angoitensin mechanism

2. Different classes of drugs for hypertension

3. Classification of and adrenoceptor blockers

4. Diuretics used for the treatment of hypertension

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Autonomic and hormonal controlofcardiovascular function

The prime determinents of arterial blood pressure

are cardiac output ( heart rate and stroke volume)

and systemic vascular resistance

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Hypertension

Definition Aetiology - primary

secondary causes

Risk factors -age, gender, dietary habit,

obesity, stress, physical inactivity,

tobacco and alcohol, genetics

Complications- MI,stroke,CRF

Management - avoid the risk factors

antihypertensives

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Different classes of antihypertensives

1. Diureticsthiazides

2. adrenoceptor blockersphentolamine, phenoxybenzamine, prazosin

3. adrenoceptor blockers

propranalol, atenolol4. Calcium channel blockers

nifedipine, diltiazem5. Angiotensin converting enzyme inhibitors

captopril6 . Angiotensin receptor blockerslosartan,

7. Direct vasodilatorshydralazine

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Alpha adrenoceptor blockers

Mechanism of action

Reversible or irreversible binding of the drug

molecules with 1 ( vascular smooth muscle)and 2 ( presynaptic adrenergic nerve terminal)

receptors lower peripheral resistance & BP

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Phenoxybenzamine

irreversible binding with receptor

both 1 and 2 receptor blocker

Phentolamine

reversible binding with receptor

both 1 and 2 receptor blocker

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Prazosin

selective 1 receptorblocker

relaxation of both arterial and venoussmooth muscle

General side effects of receptorblockers

postural hypotension ( orthostatic hypotension )

reflex tachycardia

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Therapeutic uses

Phentolamine is used inPheochromocytoma

Hypertensive emergency

Prazocin is used inMild to moderate hypertension

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Beta adrenoeceptor blockers

1 receptors - at postsynaptic cardiac muscle cells

2 receptors - at postsynaptic bronchial smoothmuscle cells

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Propranolol

The first blocker used to treat hypertension and IHDNonselective blocker with no ISATherapeutic uses- hypertension

angina (IHD)Adversed effects- AV block

masked hypoglycemia in diabeticsbronchospasm

rebound hypertensionContraindicated in bronchial asthma ,COPDheart blockperipheral vascular disease

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Atenolol

1 selective blocker or cardioselective

Therapeutic uses

hypertension ischemic heart disease safer to use in diabetics ,

asthmatics and

peripheral vascular disease risk of rebound hypertension

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Diuretics

Thiazide diureticsHydrochlorothiazideMOA inhibits NaCl transport in

distal convoluted tubule(DCT) of the kidney

Therapeutic usesmild to moderate hypertensionAdverse effects compete with the secretion of uric acid

elevation of serum uric acid (hyperuricemia)

hypeglycemia hyperlipidaemia

allergic reaction because thiazidesare sulfonamides