Diuretics
β-blockers
· They are block β-adrenoceptor in the heart thus decrease cardiac output
thus decrease BP.
· Propranolol and Nadolol are a non-selective β-blocker.
· Metoprolol, Atenolol, Esmolol, Bisoprolol and Nebivolol are selective
β1- blockers. (All β-blockers should be gradually tapered off).
· Carvedilol, Metoprolol and Bisoprolol are only B-blockers may be used in
congestive heart failure (CHF).
· Nebivolol induce releases of nitric oxide and causes VD.
· Esmolol is an ultra-short-acting, half-life about 10 minutes.
· Acebutolol, Pindolol, Celiprolol, Oxprenolol and Penbutolol are partial
agonists, i.e., β-blocker with some intrinsic sympathomimetic activity (ISA).
· Labetalol and Carvedilol are a non-selective β-blocker and selective α1- blocker
ACE Inhibitors
· Angiotensin-Converting Enzyme Inhibitors such as:
Captopril. Isinopril, Enalapril, Fosinopril, Perindoprll and Ramipril. ·
· ACE inhibitors are first-line drugs for hypertensive patients with diabetes, chronic kidney disease, & patients with coronary artery disease
· The hypotensive activity of ACE inhibitors, due to;
1) Blocks the conversion of angiotensin I to angiotensin II.
2) Inhibits the degradation of bradykinin cause VD via NO release.
· Avoid other drugs that increase K+ level e.g. ARBS, Aliskiren and K+
sparing.
· ACEIs may develop dry persistence cough and angioedema; due to increase
levels of bradykinin and substance Persistent
· Can be treated by:
1) Iron supplements (an inhibitor of NO synthase)
2) NSAIDS (e.g. aspirin).
· ACEIs are contraindicated with pregnancy; increase risk of fetal malformation.
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ARBs
· Angiotensin II Receptor
Blockers:
Losartan, Valsartan, Candesartan & Irbesartan.
· ARBS have a similar uses
and precautions to ACE inhibitors, but less in cough.
Direct Renin Inhibitors
· Aliskiren is the first and
only drug available.
· It is act by binding to
active site of renin
· decreasing plasma renin
activity thus inhibiting conversion of angiotensinogen to angiotensin I.
· Has a similar uses and
precautions but Angioedema and cough; less common.
· Most common side effects:
Diarrhea, Gl symptoms and rash, headache and dizziness.
α-blockers
· Prazosin, Doxazosin and
Terazosin are selective competitive α1 receptors blockers.
· Acts by blocking
α1-adrenoceptors on vascular smooth muscle thus make VD thus decrease PVR thus
decrease BP.
· Used mainly in men with
hypertension and benign prostatic hyperplasia (BPH).
· Most common side effects are
first-dose orthostatic hypotension (Initial syncope attack or first-dose
phenomenon)
Calcium Channel Blockers (CCBS)
I. Dihydropyridines:
· Nifedipine (is the
prototype), Amlodipine, Felodipine, Isradipine, Lacidipine, Nicardipine,
Lercanidipine and Nitrendipine
· have a much greater
affinity for vascular calcium channels than for calcium channels in the heart.
II. non-dihydropyridines:
· Verapamil a CCB that is a
class IV anti-arrhythmia agent, much effects on cardiac CC.
· Diltiazem affects both
cardiac and vascular smooth muscle.
· Side effects: Verapamil;
First-degree atrioventricular block and constipation.
· Dihydropyridines S.E:
Dizziness, headache, fatigue and peripheral
Centrally Acting Sympathetic Inhibitors
· Clonidine is an α2 agonist
(centrally and peripherally) that is used for the treatment of hypertension.
· It decreases blood pressure
by;
1) Stimulate presynaptic α2
receptors: decrease Presynaptic Ca+2 thus decrease NE release.
2) Stimulate central α2
receptors: decrease Sympathetic vasomotor centers thus decrease Sympathetic
outflow thus decrease NE release thus decrease renin release.
3) Stimulate l1: (Imidazoline)
receptor: Sympatho-inhibitory action.
· Clonidine therapy should be
gradually tapered off; Clonidine suppresses sympathetic outflow, but sudden
discontinuation can cause rebound hypertension (life-threating hypertensive
crisis) due to a rebound in sympathetic outflow.
· Methyldopa is an a agonist
that has both central and peripheral effects.
· It decreases blood pressure
by:
1) Methyldopa is converted
into the false transmitter called: alpha-methyl-norepinephrine, in the CNS thus
the false transmitter is central α2- agonist thus decrease sympathetic outflow
thus decrease NE release thus decrease renin release.
2) It is a competitive
inhibitor of dopa-decarboxylase enzyme which converts L- dopa into dopamine.
· Dopamine is a precursor for
NE and subsequently epinephrine.
· Mainly used for management
of hypertension in pregnancy (category B).
Peripherally Acting Sympathetic Inhibitors
· Guanethidine and Reserpine
acts by reduces the release of catecholamines, such as NE.
· Trimethaphan used in
emergency, while Mecamylamine used in moderate hypertension.
Vasodilators
· Hydralazine is a direct
vasodilator (arterioles but not veins).
· Uses: Severe hypertension,
with nitrates for CHF in African American, and in HTN in pregnancy.
· Sodium Nitroprusside is a
powerful short acting that is used in emergency.
· Fenoldopam is an agonist of
peripheral dopamine D1 receptors that is used in emergency.
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