Which statement regarding hydralazine hydrochloride's mechanism of action is correct?

Hydralazine hydrochloride is a vasodilator that primarily acts by directly relaxing the smooth muscles of blood vessels, particularly arterioles. This action reduces peripheral vascular resistance, leading to a decrease in blood pressure. The drug's mechanism of action allows for greater dilation of arterioles compared to veins, ultimately resulting in less resistance for blood flow and reducing the workload on the heart.

The significance in selecting this statement lies in understanding that hydralazine's primary effect is on the arterioles, which contribute more significantly to systemic vascular resistance compared to veins. Thus, by targeting arterioles, hydralazine effectively lowers blood pressure and can help treat conditions such as hypertension and heart failure.

Other statements do not accurately reflect hydralazine's pharmacological properties. For instance, suggesting it affects only large blood vessels misrepresents its mechanism since its primary action is on arterioles, which are smaller. Furthermore, categorizing it solely as a sympathomimetic agent overlooks its unique properties as a direct vasodilator, which differs fundamentally from sympathomimetics that typically enhance sympathetic nervous system activity.