The same applies to Sildenafil or Viagra. You can take it in a small dose daily or in a larger dose as needed. Sildenafil was invented back in the late s by scientists working for American pharmaceutical company, Pfizer. We also looked at additional services, such as access to digital pharmacies and home delivery options. The drug allows the blood vessels in the penis to relax and expand, boosting the blood flow to the area and making it easier to maintain a lasting erection.Sildenafil oral tablet is a prescription medication used to treat erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). Sildenafil can be taken . Cost: Consultation prices vary based on the prescriber; $5 generic prescriptions Medical Consultation Required: Yes Medications Prescribed: Viagra, Cialis, . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes .