Cialis and Viagra: Not That Kind of Performance Enhancement!

projectblueoptimiz

Oct 7

7 min read

Phosphodiesterase type 5 inhibitors were designed as heart drugs. They became famous for an entirely different organ. That origin story is not trivia. It is the reason a class of medications most people associate with a late-night commercial is now being discussed, with a straight face, in longevity clinics, cardiology journals, and podcasts that treat 5 mg of tadalafil like a morning vitamin.

The question is not whether sildenafil (Viagra) and tadalafil (Cialis) do something beyond erectile function. They do. Both are FDA-approved for pulmonary arterial hypertension. Tadalafil 5 mg daily is approved for lower urinary tract symptoms from benign prostatic hyperplasia. The interesting question is whether the same nitric-oxide / cGMP plumbing that relaxes vascular smooth muscle also moves the needle on aging, cancer, cognition, or hair, and whether healthy people should take them for those reasons.

Short version: the cardiovascular signal is the strongest part of the story. Almost everything else is earlier, messier, or both. Nobody should start a prescription longevity stack because a database study looked impressive on a slide.

How these drugs actually work

PDE5 breaks down cyclic GMP, the second messenger that lets nitric oxide relax blood vessels. Block PDE5 and cGMP lasts longer. Smooth muscle relaxes. Blood flow improves. That is the entire party trick, applied wherever PDE5 is expressed: corpus cavernosum, pulmonary arteries, prostate and bladder neck, systemic endothelium, and, to a more limited extent, cerebral vessels.

Tadalafil lasts longer than sildenafil, a half-life of roughly 17 hours versus 3 to 5, which is why daily low-dose tadalafil (2.5–5 mg) is the formulation longevity circles keep circling. Continuous, low-level endothelial exposure is a different pharmacologic object than a 50 mg tablet taken on a Saturday.

The claim with the best evidence: heart and death

This is the part of the conversation that has earned a place in the medical literature rather than just the comment section.

A 2024 systematic review and meta-analysis in the European Heart Journal, Cardiovascular Pharmacotherapy pooled 16 studies and more than 1.25 million people, nearly all men, followed a median of 4.3 years. PDE5 inhibitor use was associated with a 22% lower risk of major adverse cardiovascular events and a 30% lower risk of all-cause death.

That is not a one-off. Kloner’s claims analysis of tadalafil-exposed men found lower rates of unstable angina, coronary revascularization, cardiovascular death (about 55% lower), and all-cause mortality (about 44% lower), with a suggestion of a dose–response: more exposure, fewer events. A 2025 TriNetX analysis in The American Journal of Medicine (Jehle and colleagues) looked at more than 500,000 men with erectile dysfunction and over a million with lower urinary tract symptoms. Tadalafil and sildenafil were both associated with lower all-cause mortality, myocardial infarction, stroke, venous thromboembolism, and dementia; tadalafil generally looked stronger. Earlier work in men with type 2 diabetes and in Swedish men after myocardial infarction pointed the same direction.

Before anyone prints a T-shirt: these are observational studies. Men who get a PDE5 inhibitor prescription tend to be men who still have a sex life, a doctor, insurance, and enough vascular reserve to be offered the drug. Matching and propensity scores help. They do not invent a randomized trial. Healthy-user bias is the ghost in every one of these datasets. The signal is consistent enough that it should not be dismissed. It is not yet a mandate to put tadalafil in the water supply.

Mechanistically, the story is at least coherent. PDE5 inhibitors improve endothelial function and flow-mediated dilation. They are mild vasodilators. Some data suggest anti-inflammatory effects. Daily tadalafil 5 mg has been shown, in a small randomized study, to increase abdominal lean mass and improve endothelial measures over two months in non-obese men with mild erectile or urinary symptoms — an interesting finding, not a body-composition protocol.

The brain: a loud first paper, then a more complicated chorus

In 2021 a Cleveland Clinic analysis of insurance claims on more than seven million people reported that sildenafil users had about a 69% lower incidence of Alzheimer’s disease over six years. That number did what large, surprising numbers do. It traveled.

Follow-up has been less cinematic. A 2024 UK primary-care cohort in Neurology (Adesuyan et al.) of 269,725 men with erectile dysfunction found an 18% lower adjusted risk of Alzheimer’s among PDE5 inhibitor initiators, and a larger association among men with more than 20 prescriptions. The American Journal of Medicine analysis above also reported lower dementia rates. A later meta-analysis of several observational studies again found lower Alzheimer’s incidence.

Then there is the study that used a better comparison group. The NIH-supported DREAM analysis compared PDE5 inhibitor initiators with endothelin-receptor antagonist initiators among patients with pulmonary arterial hypertension, two drug classes used for the same disease, and found no reduction in Alzheimer’s or related dementia across four analytic approaches designed to beat common biases. Cell assays in that paper also failed to show a clean Alzheimer’s-protective phenotype for sildenafil. Mendelian randomization work has similarly not confirmed a causal link.

Small human studies show modest changes in cerebral blood flow; they do not show that cognitively healthy adults get smarter on these drugs. Animal data are friendlier than human data usually are. Bottom line: the brain story is a hypothesis with mixed human evidence, not a prevention strategy.

Cancer: two stories that refuse to be one story

People claim PDE5 inhibitors both cause cancer and treat it. The literature, unhelpfully, contains versions of both.

On the “maybe helpful” side: a Swedish analysis of men with colorectal cancer found post-diagnostic PDE5 inhibitor use associated with lower cancer-specific mortality and lower metastasis risk, especially after open surgery. Preclinical work has long suggested immune effects, less myeloid-derived suppressor cell activity, more cytotoxic function. In 2026, a Cancer Research paper reported that PDE5A inhibition traps cholesterol in lysosomes via a cGMP–NPC1 interaction, impairing cancer-cell migration. Combining sildenafil with a statin looked additive in models, and electronic health records in that program associated sildenafil use, particularly with statins, with better survival among cancer patients. A large propensity-matched pan-cancer look at TriNetX also reported better overall survival in exposed patients. These are signals, not adjuvant-therapy guidelines.

On the “maybe harmful” side: several observational studies and a meta-analysis reported a small increase in melanoma and basal cell carcinoma among PDE5 inhibitor users. The more careful analyses have argued this is confounding by sun exposure, men using these drugs also generate more solar keratoses and basal cell cancers, which is what you would expect if they spend more time outdoors, not if the pill is mutagenic. There is no good evidence of a dose–response that would make a pharmacologic story tidy.

Net: do not take Cialis to treat cancer. Do not stop a needed prescription because of a melanoma headline. If you have a personal or family melanoma history, mention the drug class to the clinician who is actually managing your skin.

Hair loss: the claim that did not survive contact with dermatology

This one can be retired quickly. A systematic review of phosphodiesterase inhibitors for alopecia found most of the human data on topical caffeine (a non-selective PDE story) for androgenetic alopecia or telogen effluvium, plus scattered work on topical sildenafil for pediatric alopecia areata and oral apremilast (a PDE4 inhibitor) for alopecia areata. That is not Cialis. The evidence-based treatments for male-pattern hair loss remain topical minoxidil and 5-alpha-reductase inhibitors. If someone on the internet is selling you tadalafil as a hair protocol, they are selling you a protocol.

What else gets claimed

Approved, not speculative. Pulmonary arterial hypertension and, for tadalafil 5 mg daily, BPH/LUTS. Those are labeled uses with trial programs behind them.

Plausible but secondary. Mild blood-pressure reduction (a few mmHg). Improved exercise tolerance in some cardiac populations. High-altitude pulmonary hemodynamics in small studies. None of that makes tadalafil an endurance ergogenic at sea level.

Mostly noise. General “anti-aging,” skin quality, athletic “pump” as a training adaptation, and broad metabolic reset. Endothelial health is relevant to aging. That does not make PDE5 inhibition a senolytic, an epigenetic reprogrammer, or a substitute for VO2 work, sleep, and not eating like a chaotic person.

Should you take them?

If you have an approved indication — erectile dysfunction, BPH symptoms, or pulmonary hypertension — the longevity conversation is a bonus hypothesis attached to a drug you may already have a reason to use. Daily tadalafil 5 mg is often the cleaner regimen for men who also have urinary symptoms.

If you are a healthy athlete looking for a healthspan edge, the honest answer is: maybe interesting, not ready. There is no large randomized trial of low-dose tadalafil for primary prevention in people without erectile dysfunction or BPH. The mortality associations come from men who already had a reason to be prescribed the drug. Women are almost absent from the outcome literature that longevity Twitter quotes.

Safety is not theoretical. The combination with any organic nitrate — nitroglycerin, isosorbide, amyl nitrite / “poppers” — can produce profound hypotension. That is an absolute contraindication, and tadalafil’s long half-life means the washout is measured in a couple of days, not a couple of hours. Caution also applies with riociguat, some alpha-blockers, recent unstable coronary syndromes, and severe hypotension. Common effects are pedestrian: headache, flushing, nasal congestion, dyspepsia, back pain or myalgia. Rare visual or auditory events exist in the label. This is a real drug, not a supplement with a PDF.

Project Blue’s bias is the same one we bring to every shiny molecule: measure the physiology first. Endothelial function, blood pressure, lactate, VO2, sleep, and the boring metabolic labs still explain more of a 45-year-old athlete’s trajectory than a 5 mg tablet. If a clinician and a patient decide daily tadalafil is reasonable, approved indication, clean medication list, no nitrates, follow-up planned, that is medicine. If the plan is “Bryan Johnson takes it, therefore I will,” that is cosplay.

The grown-up summary

PDE5 inhibitors are old, cheap, reasonably well understood vasodilators with a consistent observational association with fewer cardiovascular events and lower mortality in men who were prescribed them for other reasons. The dementia signal is mixed. The cancer literature points both ways and is not ready for the clinic. The hair-loss claim is a category error. Anti-aging, as a marketing noun, is doing more work than the trials.