Antiangina

Antianginal Drugs

Dr Laith M Abbas Al-Huseini
M.B.Ch.B, M.Sc., M.Res., Ph.D.

Myocardial Preconditioning

Single or multiple brief periods of ischemia result in a marked reduction in infarct size when the hearts are exposed to a more prolonged period of ischemia.
Has 2 phases:Acute and Delayed PC
Acute phase lasts 1-2 Hours
Delayed phase lasts 24-72 Hours
Nitrogycerin(GTN) produces delayed PC in animal and clinical studies.
This effect persists even in the presence of tolerance to its vasodilator effects


" Decrease in the effect of a drug
when administered in a long-acting form"
NITRATESTOLERANCE
Develops with all nitrates

Is dose-dependent

Disappears in 24 h. after stopping the drug

Tolerance can be avoided

- Using the least effective dose
- Creating discontinuous plasma levels

NITRATES

CONTRAINDICATIONS
Previous hypersensitivity
Hypotension ( < 80 mmHg)
AMI with low ventricular filling pressure
1st trimester of pregnancy


WITH CAUTION:
• Constrictive pericarditis
• Intracranial hypertension
• Hypertrophic cardiomyopathy

ß-ADRENERGIC BLOCKERS

CONTRAINDICATIONS
Hypotension: BP < 100 mmHg
Bradycardia: HR < 50 bpm
Chronic bronchitis, ASTHMA
Severe chronic renal insufficiency

Reasons for Using Nitrates and Beta Blockers in Combination in Angina

Beta Blockers prevent reflex tachycardia and contractility produced by nitrate-induced hypotension.
Nitrates prevent any coronary vasospasm produced by Beta Blockers.
Nitrates prevent increases in left ventricular filling pressure or preload resulting from the negative inotropic effects produced by Beta Blockers.
Nitrates and Beta Blockers both reduce myocardial oxygen consumption by different mechanisms.
Nitrates and Beta Blockers both increase subendocardial blood flow by different mechanisms