Science and Research

Sildenafil Citrate vs. Sildenafil: What's The Difference?

May 3, 2021

Medically reviewed by

David Culpepper, MD

Sometimes a brand name is so popular that it becomes synonymous with an item.

Chapstick instead of lip balm, Jacuzzi instead of hot tub, and Crock Pot instead of slow cooker. 

Another example of this phenomena is Viagra®. Viagra is the brand name for the medication and active ingredient sildenafil citrate. Viagra is just one oral medication option among many that can treat erectile dysfunction. 

The differences between sildenafil citrate (Viagra) and the generic sildenafil are few in terms of effectiveness, but many in terms of branding.

The History of Sildenafil Citrate, AKA Viagra  

In the late 1980s, Pfizer chemists were researching a new potential treatment for high blood pressure called sildenafil. Initially it looked as though sildenafil could be a good match for treating angina, a form of chest pain, but they found results in humans were not particularly promising. 

What they did discover was how effective sildenafil could be at producing erections in men.

After a few more years of research and clinical trials, Pfizer successfully patented sildenafil, and two years later it would be approved by the Food and Drug Administration as an effective treatment for erectile dysfunction, in 1998.

Viagra hit the shelves, and the world was never the same. While sildenafil can still be used to treat high blood pressure (more on that later) it’s primarily used to help men achieve and maintain erections strong enough for sexual intercourse. Things would change in 2017 as the patent for Viagra expired, allowing for the sale of generic sildenafil at much lower prices. Generic drugmakers flooded in from 2017 to 2020, and today a variety of companies manufacture generic sildenafil. 

Most generic sildenafil products are simply labeled as “sildenafil,” but there are some manufacturers that use other names. 


What is Sildenafil and How Does It Work? 

Sildenafil is technically a phosphodiesterase type 5 (PDE5) inhibitor, which means that it helps to block the PDE5 enzyme that affects certain muscles in the penis and the heart. PDE5 can restrict blood flow to blood vessels located in the spongy penis tissue known as the corpus cavernosa. This is the tissue that helps the penis to become erect when aroused. During arousal, the corpus cavernosa fills with blood, creating an erection in much the same way air inside a balloon slowly enlarges the balloon.  

PDE5 is essentially the body's natural braking system on erections, helping to slow and reduce erections after orgasm or ejaculation.

Sildenafil and other similar medications help to stop PDE5 from restricting blood flow into these blood vessels and relax the muscles in the penis. As a result, the penis gets the blood it needs to maintain an erection. 

Typically, a dose of sildenafil will be 25mg, 50 mg, or 100 mg depending on the degree of the erectile dysfunction. Pills are to be taken within an hour of sexual activity for maximum effectiveness and will stay in the body for three to five hours. 

Other Uses For Sildenafil 

Viagra is specifically marketed to treat erectile dysfunction, but sildenafil has another use. 

Individuals that suffer from pulmonary arterial hypertension sometimes use sildenafil to treat their condition. Revatio, also made by Pfizer, is a branded medication that has the same active ingredient (sildenafil) as Viagra but is used to treat hypertension. Pulmonary arterial hypertension can cause smooth muscles in the lungs to become irritated and inflamed, which restricts blood flow to certain lung arteries. Revatio is used to relax and widen blood vessels in the lungs to reduce pulmonary blood pressure to the heart and therefore improve its function. This reduction in blood pressure helps the individual to become more active and improve their heart and lung health. 

Another stark difference between Revatio and Viagra is the size of the dose and when it’s taken. Revatio is a smaller dose than Viagra at 20mg or less, but is taken up to three times daily, whereas Viagra is only to be taken when needed. In addition, Revatio can be taken as an oral tablet, a liquid, or an injection while Viagra is strictly available in pill form. 

The Key Differences Between Viagra and Sildenafil 

For the most part, there are no differences between Viagra (sildenafil citrate) and sildenafil. The active ingredients are identical and the only differences are due to marketing. 

That’s not to say that there are no differences between sildenafil versions, however:

  • Viagra (25, 50, 100 mg) is approved to treat erectile dysfunction, while 20 mg sildenafil (Revatio) can be prescribed to treat pulmonary arterial hypertension in addition to erectile dysfunction.
  • Viagra is famous as the "little blue pill” and is diamond shaped. Sildenafil in tablet form varies in appearance by generic manufacturer, typically off-white or white in color.
  • The price is probably the most important difference to the consumer. Branded Viagra is much more expensive than generic versions of sildenafil. Despite essentially being the same thing, the brand name and recognition of Viagra means it can be sold at much higher prices. 

Ways To Maximize The Effectiveness of Sildenafil 

Viagra and sildenafil both last for three to five hour, but depending on dose can last longer. There are a few additional factors that can influence sildenafil's effectiveness, which include:


For the greatest effect, Viagra and sildenafil should be taken on an empty or light stomach, or in the absence of a high-fat meal. Eating a large, heavy, or high-fat meal prior to taking sildenafil can dramatically increase the time it takes for the body to absorb and deploy the medication. High-fat meals can make sildenafil less effective.

Stop Smoking and Avoid Alcohol 

Smoking is incredibly bad for your health in general, and this is just another reason to quit. The nicotine that’s found in tobacco is known to reduce blood flow and cause vasoconstriction, and smoking causes significant damage to the heart, lungs, blood vessels, and nerves. All of these are crucial to the process of achieving an erection. 

Alcohol in small doses is acceptable but moderate-to-heavy chronic drinking can make it much more difficult to get an erection over time. When taking Viagra or sildenafil, it’s best to avoid alcohol altogether. The combination can end up lowering your blood pressure too far, resulting in dizziness, lightheadedness, or headaches as well as making it more difficult to get an erection.

Get In The Mood 

There are many misconceptions about Viagra and how it works. People may think it’s as simple as popping a pill and getting an erection, but it’s more complex than that. 

For starters, Viagra does not work unless you are or get sexually aroused. It may take some time before it's broken down and the drug begins to kick in, but if you don't have any sexual stimuli, it generally won’t work. Foreplay and other methods of stimulation are important to how effective the medication will be.

Are There Any Side Effects? 

For the most part there are few serious side effects from taking Viagra or generic sildenafil. The most common side effects reported are headaches, indigestion, and flushing of the face or body, but even these are not frequent. 

Some possible side effects can be:

  • Headaches
  • Indigestion
  • Flushing
  • Nausea
  • Dizziness
  • Rash
  • Low blood pressure
  • Nasal congestion
  • Back pain
  • Abdominal pain
  • Blurred vision or blue tinted vision
  • Priapism (erection lasting longer than four hours)

It’s also extremely important to note that you should talk with your doctor about other medications that you may be taking before taking Viagra or sildenafil in any form. It can potentially impact these other medications and cause serious health issues. 

If you meet any of the following criteria, you should generally talk to a doctor, and sildenafil or other PDE5 inhibitors may not be appropriate:

  • Are over 65 years old
  • Take nitrates such as nitroglycerin
  • Having an existing heart condition
  • Take alpha blockers for high blood pressure
  • Have been diagnosed with Peyronie’s disease
  • Have tinnitus
  • Have liver or kidney disease
  • Have sickle cell anemia

The Takeaway

Overall the only difference between sildenafil citrate and sildenafil is related to manufacturing and marketing. Sildenafil is the active ingredient in Viagra, as well as generic forms of Viagra with the same dose, purpose, and FDA label.

From a chemical composition and scientific point of view, there are no differences between Viagra and sildenafil. The key differences are related to how it’s presented, what it can be used for, and price. 

Choosing Viagra over other forms of generic sildenafil will not necessarily help to relieve erectile dysfunction any better, but there will be a price difference. Learn more about getting ED meds delivered with Rex MD by clicking here.