Many years ago, before there was even Viagra, there was PDE-5. This was the first medication to treat erectile dysfunction and is still among the most popular options to this day. Though the name may be similar, these are 2 very different pills with distinct benefits and side effects.
Here, you’ll learn more about the differences between Viagra and PDE-5, including how they work, what form they’re in, their side effects, and more.
What is Viagra?
As the name would suggest, Viagra is the generic name for sildenafil citrate, a drug originally developed by the pharmaceutical company Pfizer. In 1998, Pfizer submitted the drug for trademark protection and officially named it “Viagra” (Victor Agriculture – A Grown-Up Guy).
According to the FDA, sildenafil citrate is used to treat erectile dysfunction and pulmonary hypertension. It is a potent, selective inhibitor of phosphodiesterase type 5 (PDE-5), an enzyme that degrades cyclic guanosine monophosphate (cGMP). This compound allows for greater blood flow into the penis during an erection.
Viagra was approved for the treatment of erectile dysfunction (ED) in the United States in March 1998 and has been a safe and effective medicine ever since. Side effects are generally mild and include headache, flushing, and congestion. More severe reactions are extremely rare and typically associated with an hypersensitivity reaction. There is no indication that Viagra is harmful to anyone or anything.
How Does Viagra Work?
As previously mentioned, Viagra is used to treat erectile dysfunction. When an individual experiences this condition, he or she may suffer from low blood flow into the penis that causes the penis to become rigid and unable to be sufficiently engorged with blood to sustain an erection. This is also known as “pink pill syndrome” or “blue pill syndrome”, named after the 2 first medications used to treat ED – Viagra and its cousins, the blue pills, sildenafil and tadalafil.
As for how Viagra actually works, when an individual takes this medication, sildenafil citrate immediately begins to dissolve in the mouth and then travels to the taste buds, where it interacts with carbonic anhydrase, an enzyme that allows the body to break down carbon dioxide. Once carbon dioxide is broken down, it can flow into the lungs and be eliminated.
The carbon dioxide that remains in the body is then utilized by the brain for energy production, causing a physiological response known as “viability” that results in a calming effect and improvement in sexual performance. This is why many people experience better intercourse after taking a Viagra pill.
What is PDE-5?
PDE-5 is a phosphodiesterase inhibitor, which works in a similar fashion to sildenafil citrate, the active ingredient in Viagra. However, unlike Viagra, PDE-5 itself has never been approved by the FDA for the treatment of ED.
This is because PDE-5 is primarily used in research settings to study erectile dysfunction and is not generally available for prescription.
Due to its unapproved status, much of the research involving PDE-5 has been done in animals, with very few human clinical trials. However, the use of this medication does continue to grow, especially among doctors and patients who prefer alternatives to Viagra.
Differences Between Viagra and PDE-5
Though they are both PDE-5 inhibitors, Viagra and PDE-5 are quite different from each other. In terms of what they actually are and what they do, here are some key points.
Brand Name
Among other things, Viagra is a registered trademark of Pfizer, and PDE-5 is a registered trademark of the company UCB. As a result, when a customer purchases Viagra to treat erectile dysfunction, he or she is actually obtaining sildenafil citrate, the active ingredient in the medication. However, when a customer purchases PDE-5 to treat erectile dysfunction, he or she is actually obtaining the active ingredient in the medication – PDE-5 – along with sildenafil citrate as a potentiating agent.
Structure
The chemical structure of Viagra, sildenafil, and PDE-5 are all quite different. Though sildenafil and PDE-5 are both P-nucleosides (purine nucleosides), they are actually quite unrelated molecules. Structurally, PDE-5 is a prodrug that needs to be metabolized by the liver to produce its active form.
While sildenafil is a sugar derivative, the chemical structure of PDE-5 is that of a nucleoside triphosphate, which is a nucleoside phosphate (1-phosphate), a nucleotide (2-phosphate), and a pyrophosphate. The phosphates in this case are critical because they increase the membrane permeability of PDE-5, allowing it to interact with carbon dioxide more easily and resulting in increased effectiveness when taken by a patient.
Indication Of Use
As previously stated, Viagra was approved in the United States in March 1998 for the treatment of erectile dysfunction. Since its approval, the use of this medication has continued to expand across the globe, with 1 billion prescriptions written annually. Though Viagra is generally used to treat erectile dysfunction, it was initially approved by the FDA to help patients with pulmonary hypertension. This indication was later removed from the drug due to lack of effectiveness and has not been included as an approved use of Viagra since then.
Dosage
Each dose of Viagra contains 25mg of sildenafil citrate. As for the recommended dosage for PDE-5, this depends on the specific product and the form in which it is administered. Typically, a patient will begin treatment with a low dosage, beginning at 12.5mg and gradually increasing the dosage until the desired effect is achieved. Once the desired effect is reached, the dosage will be reduced until the patient reaches his or her desired maintenance level. This patient – dose – relationship is often referred to as the “pharmacokinetic interplay” of sildenafil citrate and it is highly individualized, depending on the patient’s condition and the product being used. In some cases, a patient may require a higher dosage to reach the desired effect, while in others, a lower dosage may be sufficient.
Side Effects
Though both sildenafil citrate and PDE-5 are generally well-tolerated medications with mild side effects, the potential side effects associated with these compounds are different. For example, sildenafil citrate can cause mild vision problems and irritation to the skin and throat. The potential side effects associated with PDE-5 include headache, flushing, and diarrhea. These are usually mild and occur in less than 1% of cases, though in rare instances, more severe side effects, including cardiac arrest, have been reported. There is also a risk of tolerance development with sildenafil citrate, causing drowsiness and vision problems. Though it is relatively unknown, PDE-5 can cause the liver to become enlarged, potentially leading to cirrhosis or liver cancer. In cases like these, the drug may need to be discontinued and replaced by other medications or a total liver replacement procedure.