Sildenafil: Dosage, Uses, Side Effects & Drug Class

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

You may not have heard of sildenafil, but you have heard of it in other ways. In this lesson, find out what this drug is better known as, its uses, side effects, dosage information, and drug classification.

What is Sildenafil?

Have you ever heard of sildenafil? Probably not. What about its brand name of Revatio? Not as likely either. But you've definitely heard of its other brand name, Viagra, right? Well, good, because this lesson is partly about Viagra. Find out how and why as we go over sildenafil's drug class, uses, dosage information, and potential side effects in this lesson.

Drug Class

Sildenafil is a kind of phosphodiesterase type 5 (PDE5) inhibitor. Phosphodiesterase 5 is a type of enzyme in the body, a molecule that speeds up biochemical reactions. By inhibiting the action of this enzyme, sildenafil allows for the smooth muscles around our blood vessels to relax. This means the blood vessels vasodilate, or widen, as a result.


Sildenafil has two main uses. The first one deals with its use as the brand name drug Revatio. In this case, it's used to treat pulmonary arterial hypertension. In other words, high blood pressure within the arteries of the lungs. The blood pressure drops when the blood vessels expand.

Sildenafil's second use is as an oral medication you have definitely heard of, Viagra. In this context, sildenafil is used to treat erectile dysfunction, or impotence. Here, sildenafil allows for the corpus cavernosum to fill with blood, resulting in an erection. The corpus cavernosum is a sponge-like area of the penis that fills with blood during an erection.


For pulmonary hypertension, Revatio is given in one of the following ways:

  • As an injection, it's initially given as a 2.5 mg or 10 mg shot three times a day.
  • In its oral form, it's given at 5 mg or 20 mg three times a day, 4-6 hours apart.

For erectile dysfunction, Viagra is usually taken initially as a 50 mg dose, once a day, as necessary 1 hour before sexual activity. This could also be taken 30 minutes or 4 hours before activity.

Of course, always consult a doctor about this dosage information as it can vary from person to person! In addition, be sure to speak with your pharmacist or physician about drugs that may interfere with the effectiveness of these medications.

Side Effects

Taking the wrong dose can put you at greater risk of side effects. Side effects of this medication may include:

  • Heartburn
  • Diarrhea
  • Nosebleeds
  • Headache
  • Muscle aches
  • Vision changes, including sensitivity to light
  • Numbness in the arms or feet
  • Chest pain
  • Shortness of breath
  • An erection that last longer than 4 hours

You should call a doctor right away if you experience any of these or any other side effects.

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