Drugs used in coronary artery disease

Describe how nitrates are used in management of angina

Angina happens when not enough blood gets through to the cardiac muscle. Nitrates dilate resistance vessels, including the coronary arteries supplying the heart, thus increasing the blood supply to the heart. The two main nitrates are glyceryl trinitrate (GTN) and isosorbide dinitrate. They are converted to nitric oxide via organic nitrate ester reductase, and the nitric oxide produced goes onto cause relaxation of vascular smooth muscle.

GTN and isosorbide mononitrate differ in terms of their pharmacokinetics. GTN has very high first-pass metabolism, meaning that if you try to give it orally, it will be broken down by the liver and you won't get much use out of the drug. Therefore, GTN is usually given by sublingual spray or transcutaneous patch, or by IV in severe cases. Isosorbide mononitrate has a lower first-pass clearance and can be given orally.

Another thing to keep in mind with nitrates is that they can lose their effectiveness quickly. If nitrates are used constantly over 24 hours, they lose their effect- a process called "tachyphylaxis." Therefore, if people are using transcutaneous GTN patches, the patches need to be taken off overnight.

Describe how antiplatelet agents, beta adrenoreceptor blockers, thrombolytics and anticoagulants are used in the context of ischaemic heart disease

This lecture basically covered emergency situations ("acute coronary syndromes"), including unstable angina, non-ST elevation acute myocardial infarction, and ST-elevation acute myocardial infarction (STEMI). (ST-elevation refers to a feature of the ECG tracing.)

Antiplatelet agents

Antiplatelet agents are drugs that block various actions of platelets. I've covered them here. Aspirin and clopidogrel (an ADP receptor antagonist) are good for inhibiting platelet aggregation on coronary plaques.

Beta-adrenoceptor blockers

Beta-blockers, as discussed here, reduce the contractility and rate of the heart. In turn, this reduces the heart's demand for oxygen so that it can make do with less oxygen than before. In acute coronary syndromes, beta-blockers help to limit the size of the infarct and reduce pain.

Thrombolytics

Thrombolytics (a.k.a. profibrinolytics) are good when urgent thrombolysis is needed (i.e. you need to get rid of a blood clot NOW, not prevent them from happening in the future). I have discussed them here.

Anticoagulants

Anticoagulants are good for preventing clots from happening in the future. One of the main ones that is used is low molecular weight heparin, which can prevent thrombotic and embolic complications of heart attacks. I have discussed these here.