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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