The mechanism of action for ED pills is simple: They inhibit the PDE5 enzyme which regulates the signals responsible for the smooth muscle tissue. Medical consultations were also taken into consideration, as PDE5 inhibitors require a valid prescription from a licensed medical provider. It’s available in 50 mg, mg, and mg tablets. Why is it called generic Cialis? Some platforms have a digital pharmacy that ships the medication to your home, while others send an electronic prescription to your local pharmacy. Finally, we checked customer reviews to better understand user experiences with each platform. However, some states require a live video consultation.Viagra Most common PDE5 drug that lasts in your system for 4 – 6 hours. Cialis Most common fast-acting PDE5 drug that lasts in your system for up to 18 hours. Sildenafil PDE5 drug that lasts in your system for 4 – 6 hours. Tadalafil Fast-acting PDE5 drug that lasts in your system for up to 18 hours. Medication name Sildenafil 20mg. Tadalafil (Cialis) is a phosphodiesterase-5 enzyme (PDE-5) inhibitor. It works by blocking PDE This is a protein in your body that breaks down the molecules that normally cause an erection. When it blocks PDE-5, tadalafil (Cialis) helps an erection occur by allowing certain muscles in the penis to relax and the penis to fill with blood. Many providers sell Cialis online — learn about the safest and most discreet providers here. Cialis (tadalafil) is a prescription medication for those with erectile dysfunction.