Common side effects include headache, facial flushing, indigestion, and dizziness. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. This information is reviewed by a licensed practitioner who will assess your eligibility for the medication. Common ones include: Flushing of the skin. Those who don’t feel comfortable discussing ED with an in-person provider or lack time to visit a doctor’s office may find online ED prescriptions beneficial. Medicines that you take by mouth are called oral medicines.You should also avoid products you can buy online without a prescription that claim either to be generic forms of sildenafil or to contain sildenafil. (Sildenafil is the active drug in . When you buy from an unknown company, you run the risk of getting counterfeit medicines. By some estimates, more than half of all ED drugs sold online are fakes. Some of these . Generic Viagra (sildenafil): Starting at $24/month; Generic Cialis (tadalafil): Starting at $39/month; Generic Cialis Daily (tadalafil): Starting at $89/month; Branded Viagra: .