Anti anginal Drugs pdf - D. Tayser

STAGE

Pharmacology

Anti anginal drugs

Pathophysiological definition of angina pectoris ; is imbalance between oxygen demand or
requirement by heart and oxygen supply to it ; due to defect in coronary arteries through
partial block by thrombus or atherosclerosis ; sometimes coronary arteries are normal , but
there is spasm of arteries lead to inadequate blood supply to myocardium .

So, anti anginal drugs act by :-

1)Increase oxygen supply to heart by :-

a-dilating coronary arteries .

b- Slowing the heart rate ( because coronary blood flow occur during diastole ) .

2) Reduction the demand by :-

a- reducing after load ( peripheral resistance ) .

b- reducing pre load ( venous filling pressure ) .

c- Slowing heart rate .

Anti anginal drugs :-

esid )

trinitrate (Ang

1) Nitrate group ; include Glycerial

Is a drug of choice in treatment acute form of angina pectoris ,it is potent vasodilator ,it
relaxes smooth muscles of blood vessels ( on venous side more than arterial side ), lead to
decrease in preload and after load on the heart lead to reduce myocardial oxygen and
energy demand

On venous side lead to decrease venous return to heart lead to decrease ventricular volume
and consequently lead decrease left ventricular diastolic pressure .

On arterial side lead to decrease arterial blood pressure lead to reduction ejection time by
this decrease heart work and decrease oxygen and energy demand and overcome on the
anginal pectoris ,beside increase oxygen supply to heart by increase coronary vasodilatation

GTN, has very quick onset of action within 5 minutes when taken sublingually , its half life is
5 minutes and duration of action 20-30 minutes ;GTN, not used orally because it has
extensive first effect in the liver ,it is given sublingually 0.5 mg at beginning of anginal
pectoris or when there is anticipated of angina .

Side effects :

1)Headache ( throbbing or bursting in nature ) occur due to stretching of pain sensitive
tissues around the meningeal arteries .

2) Flushing .

3) Reflex tachycardia .

4) Hypotension .

5) Methaemoglobinaemia occur with heavy dosage .

GTN; present as tablet ,lingual spray , ointment or cream for skin on chest ,transdermal
patch or paste (5-10mg ) once or twice per day .

2) Oral preparation of nitrate is called Isosorbide mononitrate and Isosorbide dinitrate
;specific for oral use because it is not destroyed by hepatic enzymes ;it causes relaxation of
blood vessels ,longer half life than GTN (about 20 minutes ) , duration of action 2 hours .

Used in chronic cases of angina pectoris and as prophylaxis to prevent further attack .

Tolerance, occur by frequent use of Nitrate group ,so either by withdrawal for short time (12
hours ) or by using Nicorandil which is specific for resistant cases .

adrenoceptor antagonists

–

Mechanism of action through lowing cardiac oxygen demand by reducing heart rate ,blood
pressure and myocardial contractility ; β1- blockers advisable to use one daily as
cardioselective drugs e.g. Atenolol 50-100 mg , Metoprolol 200mg daily , Bisoprolol (5-10mg
daily ) ; while β2 receptor of heart will be free and mediated vasodilatation and
bronchodilatation .

β- blockers should not withdrawal abruptly ,because this precipitate dangerous arrhythmias
,worsening angina or M.I. ( The β –blockers withdrawal syndrome ).

Oxprenolol and Pindolol have partial agonist (intrinsic sympathomimetic activity ) and
therefore ;tend to cause less bradycardia .

Propranolol ; needed high doses because extensive first pass effect ,beside it lipid soluble
can cross the BBB and cause side effects like nightmares ,drowsiness .

Other possible side effects of beta blockers ; exacerbate cardiac failure and peripheral
vascular diseases ;provoke bronchospasm in patients with obstructive airway disease .

blockers

channel

–

4) Calcium

Mode of action by inhibiting the slow current of calcium ions to the smooth muscles of
arteries and myocardium lead to reduce myocardial contractility and reduce blood pressure
and this decrease the oxygen demand of heart and therefore; useful in coronary spasm e.g.
Amlodipine ; Nifedipine And Nicardipine ;cause reflex tachycardia counteract by using β –
blockers ;while Diltiazem and Verapamil useful in patient not used β –blocker because they
inhibit conduction through AV node and cause bradycardia .

effects :

Side

Calcium channel blockers reduce the heart contractility and may precipitate heart failure
,peripheral edema ,flushing ,headache , dizziness .

4) Potassium –channel activators e.g. Nicorandil ; has venous dilatation and arterial

dilatation without tolerance as seen with nitrate .

For treatment of angina ; low dose of Aspirin +GTN sublingually + β –blocker ; then added
calcium channel blocker or long acting nitrate .