DRUGS FOR ANGINA: NITRATES
The three main classes of drug used are nitrates, beta-blockers, and calcium antagonists:
Nitrates
The main effect of nitrates is on the large veins, causing blood to pool in them. Less blood returns to the heart at one time so the pressure created inside the heart as it fills is less. This reduces wall tension in the heart, lowering the “preload.” The muscle does less work and therefore needs less oxygen.
Nitrates also open up the smaller arteries in the periphery of the body, the arms and legs for instance; the heart muscles can pump blood more easily through wider bore vessels. By decreasing the “afterload,” the heart muscle again does less work and needs less oxygen.
By dilating collateral channels, nitrates appear to distribute the blood that enters the coronary circulation to areas that may have been deprived during angina attacks. In all three ways, these medicines help return the supply-demand equation normal.
Nitrates can be fast-acting or long-acting. Fast-acting ones such as sublingual nitroglycerine are used to stop angina attacks once they have begun. As soon as the attack begins, stop what you’re doing, sit down, place one fresh tablet under your tongue, and allow it to dissolve unswallowed. If the pain is not relieved in three to five minutes, repeat the medicine. The strength of the tablets and the number used before seeking medical help is determined by your doctor. Your doctor might order the medicine in the form of a spray rather than a tablet.
If you are able to anticipate an angina attack because you know that a particular level of activity leads to pain, you may be able to premedicate yourself with a tablet or spray before you start and avoid an attack altogether. You can make such a plan with your doctor.
Long-acting nitrates are used to prevent attacks throughout the day. These include isosorbide dinitrate, isosorbide mononitrate, and sustained-release nitroglycerine preparations in the form of an ointment or a transdermal patch. These avoid the side effects of headache, dizziness, or nausea that you might encounter with short-acting nitrates, but they also can lead to reduction of the beneficial effects as well. A period of eight to ten hours a day without these medicines is necessary to maintain their effectiveness. Remember that if you begin to need more and more nitrates to control your angina, your condition may be getting worse and you need to consult your doctor.
You will probably want to change the location of ointment or patch each day to avoid skin irritation. The medicine works just as well on hairless skin of the arm, side, or abdomen as it does on the chest.
*90\86\8*
