How Does Viagra (Sildenafil) Work?

To fully understand Viagra’s mechanism of action, we need to understand the following:

How an erection works

1. When you are sexually stimulated, the brain sends signals to the nerves in the penis
2. This releases Nitric oxide (to relax penile blood vessels) and cGMP (to relax penile smooth muscle).
3. This causes blood vessels to widen and fill with blood, causing an erection

How erectile dysfunction happens

1. We know that nitric oxide and cGMP cause the penis to fill with blood
2. An enzyme called PDE5 breaks down cGMP, so the penis cannot fill with blood
3. ED is caused when there is too much PDE5, breaking down the chemicals which are needed for an erection

How Viagra works

1. We know that PDE5 breaks down the chemicals that are needed for an erection
2. Viagra works by blocking PDE5
3. This means more cGMP is able to circulate freely, increasing blood flow to the penis

Viagra (Sildenafil) helps improve erectile function by increasing blood flow to the penis. Its effects are only triggered during sexual stimulation. More specifically, Viagra:

• Improves the ability to achieve an erection
  By enhancing blood flow, Viagra makes it easier to get an erection firm enough for penetration.
• Helps maintain the erection throughout sexual activity
  It supports consistent blood flow, so the erection is less likely to soften prematurely.
• Enhances firmness and rigidity
  Erections typically feel stronger and more stable because of better vascular response.
• Reduces performance anxiety for many men
  Knowing it is easier to get an erection can reduce stress, which itself is a common contributor to ED.
• Supports natural sexual response
  Viagra works with your body’s normal arousal process, helping, not replacing, the physiological mechanisms that lead to an erection.
• Allows more reliable sexual performance
  It improves success rates when an erection has been difficult to achieve or maintain.

Despite its benefits, Viagra has clear limitations.

It does not:

• Increase sexual desire or libido
  It has no effect on hormones, arousal drive, or psychological interest in sex.
• Cause an erection without sexual stimulation
  You must be mentally or physically aroused; Viagra cannot create an erection on its own.
• Work instantly
  It normally takes 30–60 minutes to start working and may take longer after a heavy meal.
  Further reading: How long does Viagra take to work?
• Make the penis permanently larger
  Any increased size during erection simply reflects improved blood flow, not permanent growth.
  Further reading: Does Viagra make your penis bigger?
• Improve stamina or help you last longer
  Viagra does not delay ejaculation or treat premature ejaculation.
  Further reading: Can Viagra make you last longer?
• Guarantee success every time
  Effectiveness can vary depending on factors like alcohol intake, stress, timing, dosage, and underlying health conditions.
• Replace medical treatment for the causes of ED
  Conditions like diabetes, hypertension, obesity, low testosterone, or psychological issues may still need separate management.
• Work well after heavy meals or excessive alcohol
  High-fat foods can delay absorption, and alcohol can impair the body’s ability to get an erection even with Viagra.
• Cure erectile dysfunction permanently
  It treats the symptoms, not the underlying cause, and must be taken before sexual activity each time.

Here’s how Viagra works step-by-step:

1. Sexual arousal triggers nitric oxide release in the penis.
2. This increases levels of cGMP, a chemical that relaxes blood vessels.
3. Viagra blocks the enzyme PDE5, which normally breaks down cGMP.
4. With higher cGMP levels, blood vessels widen, allowing more blood to enter the penis.
5. This makes it easier to achieve and maintain an erection during sexual stimulation