Antianginal Drugs : Definition, Pharmacology, Mechanism of action, Classification, Examples, List, Uses, & Side Effects
- Antianginal drugs are those that prevent, abort or terminate attacks of angina pectoris.
- All organic nitrates share the same action; differ only in time course.
- The only major action is direct nonspecific smooth muscle relaxation.
Short acting Long acting Nitroglycerine / Glyceryl trinitrate (GTN) Isosorbide dinitrate
- These drugs do not dilate coronaries or other blood vessels.
- They act by reducing cardiac work and O2 consumption (decreased heart rate, inotropic state and mean BP). This is marginal at rest.
- More importantly, β-blockers limit increase in these modalities that occurs during exercise or anxiety (due to anti-adrenergic action on heart).
- All β-blockers are nearly equally effective in decreasing frequency and severity of attacks and in increasing exercise tolerance in classical angina, but cardioselective agents (atenolol, metoprolol) are preferred over nonselective β1 +β-2 blockers (e.g. propranolol), which may worsen variant angina due to unopposed a receptor mediated coronary constriction that may accentuate the coronary spasm.
3. Ca++ channel blockers (CCBs)
- The problem of rebound worsening of angina on withdrawal after chronic use is less with CCBs than with β-blocker.
4. K+ channel opener
- There are multiple types of K+ channels, e.g. voltage dependent, Ca2+ activated, receptor operated, ATP sensitive, Na+ activated and cell volume sensitive which serve diverse functions and exhibit different sensitivities to drugs.
- As such, K+ channel openers exhibit considerable diversity in action.
- The most prominent action of K+ channel openers is smooth muscle relaxation-vascular as well as visceral: their potential clinical applications are primarily based on this property.
5. Na+ channel blockers
- E.g. Ranolazine
- Used to abort or terminate attack- GTN, Isosorbide dinitrate (sublingually)
- Used for chronic prophylaxis – All other drugs