Amplification of the vasodilatory effects of Nitroglycerin Transdermal Systems by sildenafil may result in severe hypotension. The time course and dose dependence of this interaction have not been studied. Appropriate supportive care has not been studied, but it seems reasonable to treat this as a nitrate overdose, with elevation of the extremities and with central volume expansion.
The benefits of transdermal nitroglycerin in patients with acute myocardial infarction or congestive heart failure have not been established. If one elects to use nitroglycerin in these conditions, careful clinical or hemodynamic monitoring must be used to avoid the hazards of hypotension and tachycardia.
A cardioverter/defibrillator should not be discharged through a paddle electrode that overlies a nitroglycerin transdermal patch. The arcing that may be seen in this situation is harmless in itself, but it may be associated with local current concentration that can cause damage to the paddles and burns to the patient.
There is currently no manufacturer warning information available for this drug.
Transdermal nitroglycerin is indicated for the prevention of angina pectoris due to coronary artery disease. The onset of action of transdermal nitroglycerin is not sufficiently rapid for this product to be useful in aborting an acute attack.
Nitroglycerin is 1,2,3-propanetriol, trinitrate, an organic nitrate whose structural formula is:
and whose molecular weight is 227.09. The organic nitrates are vasodilators, active on both arteries and veins.
The nitroglycerin transdermal system is a flat unit designed to provide continuous controlled release of nitroglycerin through intact skin.
The rate of release of nitroglycerin is linearly dependent upon the area of the applied system; each cm2 of applied system delivers approximately 0.026 mg of nitroglycerin per hour. Thus, the 4 cm2, 8 cm2, 16 cm2 and 24 cm2 systems deliver approximately 0.1 mg, 0.2 mg, 0.4 mg and 0.6 mg of nitroglycerin per hour, respectively.
The remainder of the nitroglycerin in each system serves as a reservoir and is not delivered in normal use. After 12 hours, for example, each system has delivered approximately 11% of its original content of nitroglycerin.
The nitroglycerin transdermal system comprises two layers as shown below. Proceeding from the visible surface towards the surface attached to the skin, these layers are: 1) a polyolefin film backing layer that is impermeable to nitroglycerin and is printed with the name of the drug and strength; 2) nitroglycerin in an acrylic pressure sensitive adhesive. Prior to use, a peelable polyester release liner, which is coated on one side with silicone, is removed from the adhesive surface. Each unit is sealed in a foil-lined pouch.
Cross section of the system: