Kidney disease that needs to be treated with dialysis. Both options require valid medical documentation, but some online services only require a health questionnaire to be filled out and reviewed for approval—meaning no face-to-face video interaction is needed. This boosts blood flow and helps you get an erection from sexual activity. These medicines are called PDE5 inhibitors. That’s not to say there aren’t just as many illegitimate sites. The four main medicines taken by mouth for erectile dysfunction are: Avanafil Stendra. Viagra is always taken as needed, usually an hour before having sex.Pros and cons at a glance Below are some advantages and disadvantages of tadalafil. Pros available in a generic form, which is cheaper than brand-name drugs . Tadalafil (Cialis). This medication is taken with or without food an hour before sex. It works for up to 36 hours. You can take it in a small dose daily or in a larger . The major difference is that Cialis lasts longer and can be taken daily, giving you erections on demand. Viagra is always taken a few hours before it’s needed and .