Navigating Cialis Side Effects on the Heart: What You Need to Know https://powpill.com/2023/08/04/what-are-the-side-effect-specifics-cialis/ Cialis is prescribed primarily to treat ED by increasing blood flow to the penis during sexual stimulation, leading to a firmer and longer-lasting erection. It achieves this by inhibiting the enzyme PDE5, which is responsible for breaking down a chemical called cGMP that relaxes the smooth muscles in the penile blood vessels, allowing increased blood flow.