Editing Antianginal (section)

===Calcium channel blockers===
[[Calcium]] [[ion]] (Ca<sup>++</sup>) antagonists ([[Calcium channel blocker]]s) are used in the treatment of chronic stable angina, and most effectively in the treatment of [[variant angina]] (directly preventing coronary artery vasospasm). They are not used in the treatment of unstable angina .

In vitro, they dilate the coronary and peripheral arteries and have negative [[inotropic]] and [[chronotropic]] effects - decreasing [[afterload]], improving myocardial efficiency, reducing [[heart rate]] and improving coronary blood flow.
''In vivo'', the vasodilation and [[hypotension]] trigger the [[baroreceptor]] reflex. Therefore, the net effect is the interplay of direct and reflex actions.

* Class I agents have the most potent negative inotropic effect and may cause heart failure.
* Class II agents do not depress conduction or contractility.
* Class III agent has negligible inotropic effect and causes almost no reflex [[tachycardia]].

Examples include Class I agents (''e.g.'', [[verapamil]]), Class II agents (''e.g.'', [[amlodipine]],<ref name="DailyMed 2019">{{cite web | title=NORVASC- amlodipine besylate tablet | website=DailyMed | date=14 March 2019 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=abd6a2ca-40c2-485c-bc53-db1c652505ed | access-date=19 December 2019|quote=Exertional Angina: In patients with exertional angina, NORVASC reduces the total peripheral resistance (afterload) against which the heart works and reduces the rate pressure product, and thus myocardial oxygen demand, at any given level of exercise.}}</ref> [[nifedipine]]), or the Class III agent [[diltiazem]].

[[Nifedipine]] is more a potent vasodilator and more effective in angina. It is in the class of [[dihydropyridine]]s and does not affect refractory period on SA node conduction.