Where this idea came from
Sildenafil is the active drug in Viagra. Viagra is a pill made by the drug company Pfizer. The FDA (the U.S. agency that approves medicines) cleared it in 1998 for erectile dysfunction, or ED. ED means a man has trouble getting or keeping an erection.
Sildenafil works by blocking an enzyme called PDE5. Blocking PDE5 relaxes blood vessels and lets more blood flow into the penis. Over the years, scientists noticed that PDE5 also shows up in other places in the body, including inside some tumors and in parts of the immune system. That made them ask a simple question: could blocking PDE5 do anything to cancer?
What lab and animal studies found
The best-known early work was done in mice. In 2006, a research team published a study in the Journal of Experimental Medicine. They found that sildenafil weakened a type of immune cell that cancer uses to hide. These cells are called myeloid-derived suppressor cells. When those cells were turned down, the mouse immune system attacked tumors harder, and tumors grew more slowly.
Other lab studies have looked at cancer cells in a dish. Some found that sildenafil or similar drugs made certain cancer cells more sensitive to chemotherapy. These are interesting results. But a mouse or a dish is not a person. Many drugs that work in mice never work in humans. So these studies are a starting point, not proof.
What human studies suggest
The strongest human data so far comes from colorectal cancer, which is cancer of the colon or rectum. In 2020, researchers in Sweden published a large study in the journal Nature Communications. They looked at thousands of men who had surgery for colorectal cancer. Men who used a PDE5 drug like sildenafil after surgery had a lower chance of the cancer spreading and a lower chance of dying from it.
Another study, published in Cancer Prevention Research in 2020, looked at records from U.S. veterans. Men who had taken PDE5 drugs seemed less likely to be diagnosed with colorectal cancer in the first place.
These are observational studies. That means scientists looked back at medical records. They did not give some men the drug and others a sugar pill. So we cannot say sildenafil caused the better outcomes. Men who take ED drugs might simply be healthier, see doctors more often, or differ in other ways. Only a randomized controlled trial, which is the gold standard, can answer that. A few small trials are testing sildenafil alongside cancer treatment, but results are early and not final.
What this does NOT mean
Sildenafil is not a cancer treatment. No health agency has approved it for cancer. Nobody should take it hoping to prevent or treat cancer. Anyone with cancer should follow their oncologist's plan.
It also does not mean sildenafil is risky for people with cancer. There is no good evidence that it raises cancer risk. If a man with a cancer history needs ED treatment, that is a normal conversation to have with a doctor.
What sildenafil is actually proven to do
Sildenafil has strong evidence for one job: treating ED. In the clinical trials that led to FDA approval, most men who took it reported better erections compared with placebo. It usually starts working in 30 to 60 minutes and lasts about 4 hours. Tadalafil, the drug in Cialis, is a cousin that lasts up to 36 hours.
Common side effects include headache, flushing, stuffy nose, and upset stomach. Sildenafil must never be mixed with nitrate heart medicines like nitroglycerin, because the combination can drop blood pressure dangerously. That is why a licensed clinician should review your health history before prescribing it.
How Zen IV Spa can help
Zen IV Spa does not treat cancer. But if ED is affecting your life, Zen IV Spa's ED program starts at $129 per month. It begins with a free video visit with a licensed clinician. If treatment makes sense, the clinician prescribes generic sildenafil or tadalafil, the same active drugs found in Viagra and Cialis, and ships it to your home in New York or New Jersey. If you want a fuller picture of your health, a nurse can also come to your home to draw labs. Learn more at zenivspa.com/sexual-wellness/ or call (332) 239-2005.
Common Questions
Does Viagra cure cancer?+
No. There is no evidence that sildenafil cures cancer. Some early research hints it might help the immune system, but that has not been proven in people.
Is it safe to take sildenafil if I had cancer?+
For most men, yes, but it depends on your overall health and other medicines. Talk with your doctor or a licensed clinician first.
Which cancer has the most research with sildenafil?+
Colorectal cancer. Two large record-based studies in 2020 linked PDE5 drug use with lower risk and less spread. These studies cannot prove cause and effect.
Should I ask my oncologist about sildenafil?+
You can ask, but do not expect it to be part of your cancer plan. Clinical trials are still testing the idea.
Does Zen IV Spa prescribe brand-name Viagra?+
Zen IV Spa prescribes generic sildenafil and generic tadalafil, which contain the same active drugs as Viagra and Cialis. A free video visit comes first.
Sources: FDA prescribing information for Viagra (sildenafil); Serafini et al., Journal of Experimental Medicine 2006; Huang et al., Nature Communications 2020 (Swedish colorectal cancer cohort); Sutton et al., Cancer Prevention Research 2020.
All treatments are medical services. Every guest is screened, and every treatment is prescribed by a licensed provider. Nothing on this page is medical advice for you personally, and the opinions summarized here belong to the doctors named, not to Zen IV Spa. Talk to a provider before starting or stopping anything.
