Answer: The short version? Psychological factors like stress, depression, or anxiety can also contribute. More serious side effects may include a drop in blood pressure or an erection that lasts longer than four hours. You can get it as both a weekend and a daily tablet. On the other hand, the generic and brand-name versions of Viagra tend to be cheaper. Generic vs.Using a mail-order pharmacy might help lower your cost for Cialis. Plus, you could get your medication without leaving home. Some Medicare plans may help cover the cost of mail-order drugs. Cialis works well for most men on the first or second attempt. In a study of men taking Cialis, on average 81% of men using the 20mg dose found it improved erections. This included: 86% of men who had mild ED; 83% of men who had moderate ED; and 72% of men who had severe ED. So if you take Cialis, the chances are high that it will work. tadalafil. erectile dysfunction (ED) benign prostatic hyperplasia, or BPH). Tadalafil (Cialis) is available both as brand-name and generic tablets. Common side effects of this medication include headache and indigestion. Tadalafil (Cialis) does interact with some medications.