Nitroglycerin must be protected from heat and light because it deactivates. Which forms are available for administration?

• A. Oral tablets only
• B. Topical ointment
• C. IV, transdermal, sublingual
• D. Inhaled powder

Answer: (C)

Nitroglycerin is highly unstable when exposed to heat and light, so it must be delivered in forms that are protected from degradation and that provide predictable, rapid or steady delivery without passing through the liver first.

Sublingual administration provides rapid absorption through the oral mucosa, delivering relief quickly for acute angina without the delay and variability of oral gut absorption. IV delivery offers immediate and precisely controllable drug levels in hospital settings, which is crucial during acute episodes or perioperative management. Transdermal administration (patches) provides a steady, continuous release over many hours, which is ideal for prophylaxis and preventing angina.

Oral tablets suffer extensive first-pass metabolism in the liver, resulting in poor and unpredictable bioavailability, so they are not suitable for rapid or reliable control. Inhaled powder is not a standard, widely used route for nitroglycerin in clinical practice, unlike the clear options of sublingual, IV, and transdermal routes.

Thus, the administration forms that are actually used for nitroglycerin are IV, transdermal, and sublingual.