Also tell them about any supplements you take. You can take it in a small dose daily or in a larger dose as needed. This applies, for example, when you want to take Tadalafil brand name Cialis instead of Viagra. Liver function: If you have poor liver function you may need lower doses of Viagra Sildenafil. If use of a nitrate-containing medication is considered medically necessary, you must wait 48 hours after the last dose of Viagra Sildenafil before taking a nitrate, and only under close medical supervision. All prescriptions are reviewed by a fully licensed pharmacist who carefully examines each and every prescription and patient medical file, ensuring the highest patient health and safety standards are met.What is Viagra? Viagra (Sildenafil) belongs to a group of medications called phosphodiesterase type 5 inhibitors. It is used for the treatment of Erectile Dysfunction . Erectile dysfunction refers to the inability of a man to get or maintain an erection firm enough for satisfying sexual activity. ED can have a negative impact on the emotional well-being of men and their partners as it can be tied to self-image and relationship difficulties. 50% of men will experience ED. It is the most common sexual problem in. What about medications like Viagra ® (sildenafil)? These medications (which also include tadalafil [Cialis ®] and vardenafil [Levitra ®]) help men who can’t get an erection because of problems with blood flow into the penis. They do not help increase sex drive, so they are not useful for treating low libido.