Methandienone Anabolic Steroids

What Is It?

Sildenafil (Viagra®) is a medication used primarily for treating erectile dysfunction (ED) in men and, more recently, for pulmonary arterial hypertension (PAH).
When taken orally, it relaxes the smooth muscle lining blood vessels, allowing increased blood flow to specific tissues.

• Erectile dysfunction: Enhances penile erection by increasing blood inflow into the corpora cavernosa during sexual stimulation.
  
• Pulmonary arterial hypertension: Dilates pulmonary arteries, reducing resistance and improving oxygenation.

How Does It Work?

Sildenafil is a selective phosphodiesterase‑5 (PDE‑5) inhibitor:

1. Sexual stimulation → NO release from endothelial cells in the penis.
   
2. NO activates guanylate cyclase → increased cyclic GMP (cGMP).
   
3. cGMP causes smooth‑muscle relaxation, allowing blood to fill the corpora cavernosa.
   
4. PDE‑5 normally degrades cGMP