Suhagra 25 mg contains Sildenafil, and after you take it, it works in a very specific way in the body and bloodstream. Where it acts in the bloodstream: Once absorbed from the stomach and intestines, sildenafil enters the systemic bloodstream, meaning it circulates throughout the entire body. However, its main functional action is not evenly spread everywhere—it targets a specific enzyme in certain tissues. Primary site of action: The drug mainly acts on blood vessels in the penile erectile tissue (corpus cavernosum). Here, it inhibits the enzyme phosphodiesterase type 5 (PDE5), which is present in the smooth muscle of these blood vessels. By blocking PDE5, it increases levels of cGMP, a chemical that relaxes blood vessel walls and improves blood flow. What this means in the bloodstream: In the bloodstream, sildenafil is simply the transport medium carrying the drug to tissues. It does not “work” inside blood cells, but rather on blood vessel walls after reaching target tissues. It also has some PDE5 activity in other vascular areas (like lungs and retina), which explains some side effects.