What is a common side effect of nitroglycerin due to its rapid onset?

The correct answer highlights a well-known side effect of nitroglycerin, which is its propensity to cause headaches. Nitroglycerin acts as a vasodilator, relaxing the smooth muscles of blood vessels and leading to an increase in blood flow. This vasodilation can trigger headaches, particularly in patients who are not accustomed to the medication. The headaches often stem from increased cerebral blood flow and can manifest as a common side effect soon after administration.

While tachycardia and hypotension can occur with nitroglycerin use, they are generally considered less common side effects directly linked to its rapid onset. Tachycardia might result from compensatory mechanisms due to hypotension but does not consistently present as a direct effect. Conversely, cyanide toxicity is not associated with nitroglycerin; it is more relevant with the use of sodium nitroprusside, which can release cyanide ions in the body. Thus, the unique association of headache with the rapid vasodilation induced by nitroglycerin underscores the importance of recognizing this side effect in clinical practice.