CENTRAL  SOUTH  DAKOTA MEDICAL NEWS
The Clinical View
by P.E. Hoffsten, M.D.
10/4/2001

MEDICAL USES OF NITROGLYCERIN

             Almost 150 years ago, nitroglycerin was invented as an explosive that is still used in dynamite.  At the time it was first discovered it was known that it caused a terrible headache if a person touched a little of it to the tongue.  Ten years later,  it was learned that nitroglycerin placed under the tongue would stop chest pain that was caused by the heart disease called angina pectoris.  It was learned that the person could use the nitroglycerin repeatedly, about 5 minutes apart if the chest pain didn’t resolve with the first dose.  If it didn’t work after 3 pills, the person needed to be seen as possibly having a heart attack.  Side effects of nitroglycerin included a drop in blood pressure,  sometimes associated with fainting if the person used it standing up or in the sitting position.

            It wasn’t until almost 100 years later that it was learned how nitroglycerin worked.  It turns out that our blood vessels are equipped with a chemical called nitrous oxide that is generated in the blood vessel wall and relaxes the smooth muscle that is in the blood vessel.  This nitrous oxide system is one of the major regulators of blood pressure.  Thus, nitroglycerin given under the tongue does two things to help a person with angina pectoris.  First, it dilates the blood vessels to the heart so that the heart gets more blood and second, it lowers the blood pressure all over the body so the heart has less work to do in pumping blood out.

            Nitroglycerin now comes in at least five different forms.  One of these is the small pill that is put under the tongue and allowed to dissolve there when a person has chest pain from angina pectoris.  The second form is the long acting nitrates which are called isosorbide dinitrate (Isordil,  Sorbitrate) or isosorbide mononitrate (Ismo, Imdur). These products have the advantage of acting over hours each day.  The advantage of Imdur and Ismo is that they are very long acting and only have to be taken once a day or twice a day.  Another way that nitroglycerin can be given is with the a skin patch or with a paste that is applied locally to the chest wall.  These patches can be placed for about 12 hours a day.  If they are left on longer than that, they become ineffective even if there is good nitroglycerin left in the patch, as the liver lacks the substances necessary to activate the nitroglycerin.  In addition, nitroglycerin can be used as a spray that may work slightly faster than the pill under the tongue.  Finally in the 1980’s, it was discovered that nitroglycerin given intravenously could be used to prevent an impending heart attack when chest pain was persistent.  There are thus five different ways nitroglycerin can be given.

            In the 1980’s, it was discovered that nitroglycerin had a use other than treating chest pain.  It was found that nitroglycerin given intravenously or with a long acting pill could decrease the amount of work that the heart had to do and thereby, give a failing heart a rest.  Now nitroglycerin is used frequently to bring blood pressures down into the normal range predictively, effectively, and quickly.

            An additional use of nitroglycerin is to dilate the blood vessels to one part of the body such as the feet.  People who have disease of the blood vessels to the feet such as diabetes can use a nitroglycerin paste in their feet at night, dilate the blood vessels and thereby improve the blood supply to the feet and stopping the aching, burning sensation that sometimes occurs.

            While nitroglycerin has wonderful therapeutic effects, it does have potential problems because it is so effective.  A recent development was the discovery that Viagra potentiates the effectiveness of nitroglycerin.  Thus, if a person uses Viagra, whatever nitroglycerin preparation they are using becomes much, much more effective and can cause very severe low blood pressures.  Therefore, any person who is using nitroglycerin has to be very careful if Viagra is to be used.

            Optimizing the use of nitroglycerin and the best route to administer it can be arranged through the providers at your local clinic.  It is ironic that such a destructive product as nitroglycerin can have such wonderful medical uses.