Tadalafil may not be safe for people with certain medical conditions, including people who have had a stroke , have coronary heart disease or retinitis pigmentosa an eye disease. Cialis will be available by prescription only. You need a prescription from a doctor to buy tadalafil. The results showed the combination to be even more effective than either medication alone. Alternatively, Cialis may be prescribed as an as-needed treatment for ED, to be taken before sexual activity.Is there an over-the-counter version of Cialis? Cialis is only available with a prescription. Some online pharmacies can provide prescriptions if the customer does not already have one. シアリスの成分「タダラフィル」の効果. 陰茎の海綿体には多くのPDE-5（5型ホスホジエステラーゼ）が存在していますが、通常時に勃起していないのはこのPDE-5の働きによるものです。. しかし、何らかの原因でPDE-5が増え過ぎると、勃起したいときにでき. 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.