In 1998, the FDA approved sildenafil — branded as Viagra — and changed the conversation around erectile dysfunction overnight. The success story continued in 2005, when it received a second approval, under the name Revatio, to treat pulmonary hypertension, a serious cardiovascular condition. Sildenafil remained a household name for ED, but the breakthrough ultimately raised a broader question: how do these medications act throughout the body?
Sildenafil and tadalafil (Cialis) belong to a class of drugs called PDE-5 inhibitors, which work by relaxing the smooth muscle in blood vessel walls, improving circulation. What was originally designed to restore erectile function appears to benefit the cardiovascular system, support brain health, improve exercise tolerance, and more. Here's what the science shows.
Heart and Vascular Health
Because PDE-5 inhibitors work directly on blood vessels, their cardiovascular effects have been studied extensively. Sildenafil has been shown to improve left ventricular ejection fraction — a measure of how effectively the heart pumps blood — in patients with heart failure. It also reduces pulmonary vascular resistance, meaning the heart doesn’t have to work as hard to push blood through the lungs. In patients with heart failure secondary to pulmonary hypertension, sildenafil use was associated with lower hospitalization rates.
Tadalafil tells a similar story. In men with elevated cardiovascular risk, chronic tadalafil use significantly improved endothelial function — the health and responsiveness of the cells lining your blood vessels. What makes that finding notable is that the improvement persisted for at least two weeks after the medication was stopped, suggesting the benefit isn’t purely mechanical. In patients with type 2 diabetes, where blood vessel damage from elevated blood sugar is a serious long-term concern, sildenafil helped restore vascular function that had been compromised by the disease.
Lung Function and Exercise Capacity
The lungs are rich with the same PDE-5 enzyme these medications target, and sildenafil is already FDA-approved to treat pulmonary hypertension under the brand name Revatio. In that context, it reduces pressure in the pulmonary arteries, improves oxygenation, and has been shown to lower mortality in pediatric pulmonary hypertension. It also reduces inflammation and fibrin buildup in lung tissue — effects that go beyond simple vasodilation.
The downstream effect on exercise is meaningful. Both sildenafil and tadalafil improve exercise performance in patients with heart failure and pulmonary conditions — measured by oxygen uptake, walk distance, and overall functional capacity. In one study of healthy mountain climbers, sildenafil improved maximum exercise capacity at high altitude by lowering pulmonary artery pressure under low-oxygen conditions. These aren’t performance-enhancing effects in otherwise healthy people — they reflect how improving vascular function gives the body more room to work with.
Brain Health
This area is earlier-stage, but it’s worth paying attention to. Research has shown that sildenafil improves how blood vessels in the brain respond to stress — a marker of cerebrovascular health. In animal models of ischemic stroke, sildenafil improved recovery and appeared to stimulate the growth of new nerve cells in brain tissue adjacent to the stroke damage. The mechanism is consistent with what we see elsewhere in the body: better blood flow supports better tissue health and repair. Clinical trials in humans are still needed, but the direction of the research is promising.
Prostate Health
Tadalafil is FDA-approved not only for erectile dysfunction but also for the treatment of lower urinary tract symptoms caused by benign prostatic hyperplasia (BPH) — an enlargement of the prostate that’s common in older men. The benefit appears to come from its effect on smooth muscle in the bladder and prostate, reducing symptoms like urinary frequency, urgency, and weak stream. For men managing both ED and BPH, tadalafil can address both conditions with a single daily medication.
Sexual Wellness Beyond Erections
Research on daily low-dose tadalafil has shown meaningful improvements in sexual self-confidence, spontaneity, and overall relationship satisfaction — for both the patient and their partner. The shift from on-demand dosing to a daily regimen removes the need to plan sexual activity around a pill, which for many couples is a source of psychological pressure that compounds the physical issue. In preference studies, a significant majority of both men and their partners preferred the daily approach for exactly this reason — it restores a sense of normalcy rather than reinforcing the idea that sex requires medical preparation.
The Bottom Line
Sildenafil and tadalafil started as treatments for erectile dysfunction, but the science has moved well past that single application. Their ability to improve vascular function throughout the body has opened doors in cardiology, pulmonology, neurology, and urology — and research continues. If you’re considering ED medication, or if you’re already taking one and want to understand its broader effects, the best next step is a conversation with a qualified provider who can evaluate your full health picture and help you make an informed decision.