What is the primary therapeutic use of the drug sildenafil?

Sildenafil is primarily prescribed to treat erectile dysfunction, a condition where a man has difficulty achieving or maintaining an erection suitable for sexual intercourse. The medication works by inhibiting an enzyme called phosphodiesterase type 5 (PDE5), which leads to increased blood flow to the penis in response to sexual stimulation. This enhanced blood flow is essential for achieving and sustaining an erection.

While sildenafil can have effects on blood pressure due to its vasodilatory properties, its main indication is specifically for erectile dysfunction. The other options, such as reducing anxiety or managing heart failure, do not align with sildenafil's pharmacological effects or approved uses. Thus, the correct answer accurately reflects the drug's primary therapeutic application.