What side effect is least commonly associated with hydralazine hydrochloride?

Hydralazine hydrochloride, a vasodilator used primarily for treating hypertension, can cause several side effects due to its pharmacological action. Among the options provided, anorexia is the least commonly associated side effect.

Headaches are a frequent occurrence with hydralazine use, often attributed to the sudden drop in blood pressure that the medication can cause. Dizziness is also commonly reported as a side effect, as it can occur when blood pressure decreases. Rash is another side effect that, although less frequent than headache or dizziness, can occur, particularly in the context of drug-induced lupus-like syndrome associated with long-term use.

Anorexia, while possible, is not a well-documented side effect related to hydralazine use, making it the least commonly reported of the options listed. This understanding supports the choice that anorexia stands out in this context.