MCQ on antianginal agents: Page-4

Amyl nitrite or sodium nitrite followed by sodium thiosulphate can be used for treating cyanide poisoning. Amylnitrite or sodium nitrite will increase the binding of cyanide by converting hemoglobin to methemoglobin to which cyanide binds strongly. On the other hand, sodium thiosulphate converts cyanide into sodium thiocyanate which is less toxic than cyanide.

Ivabradine is a new drug that blocks sodium-potassium channels in pacemaker potential thereby decreases automaticity. Hence it can be used instead of betablockers.

Organic nitrates are not acting on receptors. They act by release of nitric oxide by interacting with thiol groups in enzymes. This released nitric oxide increases activity of cGMP leading to vasodilatation. Hence any modification of these leads to tolerance. Decreased release of NO, depletion of thiol groups and alteration of cGMP activity.

Verapamil decreases refractory period hence contraindicated in re-entry type arrhythmias like WPW.

Nitroglycerine sublingual tablets has fast onPage of like 2 min but short acting with duration as 30 min. Hence they can be used for symptomatic relief. Nitroglycerine sustained release tablets are given orally and they can act for 4 to 8 hr producing long term action.