When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction. Pearlman says the availability of an easy-to-access treatment for men dealing with ED is welcome news. Cialis reaches its maximum effectiveness two hours after you take it. Generic versions of sildenafil, vardenafil and tadalafil are available. Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take.1. It Targets the Problem and Works Quickly. Being a topical means MED targets your penis directly and offers a “quick onset of action,” Dr. Pearlman . (1) One difference is that tadalafil (Cialis) is approved to treat both ED and BPH whereas sildenafil (Viagra) can only be used for ED. (2) Another difference is that . Cons can cause headaches and muscle aches must be swallowed whole can cause indigestion can make you appear flushed not available over-the-counter (OTC) .