Which of the following is a common side effect of nitrates?

Nitrates are commonly used antianginal agents that work by relaxing the smooth muscles of blood vessels, leading to vasodilation. This action can result in various side effects, with headache being one of the most frequent one reported. The mechanism behind this side effect involves the dilation of cerebral blood vessels, which can lead to increased blood flow and may trigger a headache.

Since nitrates widen blood vessels, they can cause a decrease in blood pressure as well. This can prompt the body to respond with compensatory mechanisms such as tachycardia (an increased heart rate), but this is considered a less common and more indirect response compared to headache. Hypokalemia, which refers to low potassium levels in the blood, is not typically associated with nitrate use. Therefore, the predominant and commonly reported side effect of nitrates is indeed headache.