Final answer:
Nitrates are the medication group the nurse would recognize as increasing the risk associated with taking sildenafil (Viagra), due to their combined effects causing potentially severe hypotension.
Step-by-step explanation:
The patient who has high blood pressure and penile erectile dysfunction is inquiring about the safety of taking sildenafil (Viagra). Among the medications listed, the nurse would recognize that taking nitrates increases the risk associated with taking Viagra. This is because both nitrates and sildenafil affect the vasodilation signaling pathway; nitrates enhance the production of nitric oxide and cGMP, subsequently leading to vasodilation, while sildenafil works by inhibiting phosphodiesterase type 5 (PDE5), which prolongs the vasodilatory effect of cGMP within the penile tissues. Combining these medications can result in a significant and potentially dangerous drop in blood pressure.
Other antihypertensive medications such as beta-blockers, ACE inhibitors, and calcium channel blockers do not have the same pronounced interaction with sildenafil regarding systemic blood pressure. However, all patients with cardiovascular conditions should consult their physician prior to initiating sildenafil therapy due to potential cardiovascular risks.