Viagra (Sildenafil) — evidence‑based review (general information, not medical advice)

Quick summary

• Viagra is the brand name for sildenafil, a medicine primarily used for erectile dysfunction (ED).
• Strong evidence shows it improves erections for many men when sexual stimulation is present.
• It works by increasing blood flow to the penis; it does not increase sexual desire.
• Common side effects are usually mild; serious risks are uncommon but real.
• It can interact dangerously with some heart medications, especially nitrates.

What is known

What Viagra is and how it works

Viagra contains sildenafil, a drug that belongs to a group called
phosphodiesterase‑5 (PDE‑5) inhibitors. During sexual arousal, the body releases
nitric oxide in penile tissue. This triggers a chain reaction that relaxes blood
vessels and allows more blood to flow into the penis. Sildenafil slows the
breakdown of this signal, making it easier to achieve and maintain an erection.

Importantly, Viagra does not cause an erection on its own and does not act
as an aphrodisiac. Sexual stimulation is still required.

Effectiveness for erectile dysfunction

Large randomized controlled trials and decades of real‑world use show that
sildenafil improves erectile function for a substantial proportion of men with
ED. Benefits have been demonstrated in ED related to diabetes, spinal cord injury,
psychological factors, and age‑related vascular changes, although response rates
vary.

Timing and duration

Evidence indicates that sildenafil typically starts working within about
30–60 minutes and lasts for several hours. A heavy or high‑fat meal may delay its
onset. These effects are well described in regulatory documents and clinical
guidelines.

Safety profile and common side effects

The most frequently reported side effects include headache, facial flushing,
nasal congestion, indigestion, and visual color tinge (blue‑green). These effects
are usually mild to moderate and temporary.

Rare but serious adverse events have been reported, such as sudden vision or
hearing loss and prolonged erections (priapism). Causality is not always clear,
but these events warrant immediate medical attention.

Drug interactions and contraindications

Strong evidence shows that sildenafil can cause dangerous drops in blood pressure
when combined with nitrate medications (used for angina) or certain recreational
drugs containing nitrates. Caution is also required with some alpha‑blockers and
potent CYP3A4 inhibitors.

What is unclear / where evidence is limited

• Long‑term outcomes beyond sexual function: While long‑term use
  appears generally safe for many patients, data on outcomes unrelated to ED are
  limited.
• Use in women: Sildenafil has been studied for several female
  sexual or vascular conditions, but results are inconsistent and it is not
  approved for these uses.
• Cardiovascular protection or harm: Although ED can signal
  cardiovascular disease, evidence does not support using Viagra to prevent heart
  problems.
• Non‑medical or enhancement use: Benefits for people without ED
  are uncertain, and risks may outweigh any perceived advantage.

Overview of approaches

Viagra is one of several PDE‑5 inhibitors available for ED. Others include
tadalafil and vardenafil, which differ mainly in duration of action and side‑effect
profile.

Typical dosing ranges and administration instructions are defined by regulators
and manufacturers and should be followed exactly as described in official
materials. For reference only (not prescribing), see:
FDA‑approved Viagra label
and
UK NHS sildenafil guidance.

Non‑drug approaches—such as managing cardiovascular risk factors, addressing
psychological stress, and lifestyle changes—are commonly discussed alongside
medication in clinical guidelines.

Statement	Confidence level	Why
Viagra improves erections in many men with ED	High	Supported by multiple large randomized trials and guideline reviews
Viagra increases sexual desire	Low	Mechanism targets blood flow, not libido; studies do not support this claim
Side effects are usually mild and temporary	High	Consistent findings across trials and post‑marketing surveillance
Viagra prevents heart attacks	Low	No conclusive evidence for cardiovascular prevention

Practical recommendations

• General safety: Use sildenafil only if prescribed or approved
  by a qualified healthcare professional.
• When to see a doctor: If ED is new, worsening, or accompanied
  by chest pain, shortness of breath, or other systemic symptoms.
• Prepare for consultation: List current medications, past
  heart or eye conditions, and any side effects experienced.
• Seek urgent help: For erections lasting longer than four
  hours, sudden vision loss, or severe dizziness.

For related health topics, see our Sex & men’s health overview,
general health articles (Без рубрики), and recent posts in our
Blog.

Sources

• U.S. Food and Drug Administration (FDA). Viagra (sildenafil) prescribing information.
• National Health Service (NHS), UK. Sildenafil/Viagra patient guidance.
• European Association of Urology (EAU). Guidelines on Sexual and Reproductive Health.
• American Urological Association (AUA). Erectile Dysfunction Guideline.
• Mayo Clinic. Sildenafil (oral route) overview.