Phosphodiesterase type 5 (PDE5) inhibitors are a group of medications most commonly used to treat erectile dysfunction (ED). Their ability to improve symptoms of ED was discovered accidentally while researchers were examining their potential use for high blood pressure and angina.

ED is often considered the most common form of sexual dysfunction in men, and it becomes more common with age. It’s estimated that anywhere between 30 million to 50 million men in the United States deal with ED.

PDE5 inhibitors are often the first treatment option for people with ED caused by poor blood flow to the penis.

In this article, we break down the most common types of PDE5 inhibitors on the market. We also take a look at how they work, what they’re used for, and how much they cost.

Types of PDE5 Inhibitors

ED can be caused by psychological or physiological factors. PDE5 inhibitors are only effective at treating ED caused by physiological factors.

Psychotherapy or counseling are treatment options for the psychological cause of ED, such as stress or anxiety.

The four major types of PDE5 inhibitors available include:

• sildenafil (Viagra);
• tadalafil (Cialis);
• vardenafil (Levitra or Staxyn);
• avanafil (Stendra).

Let’s take a look at each.

Sildenafil (Viagra)

Sildenafil was the first extensively researched PDE5 inhibitor, and it was FDA-approved in 1998 under the name Viagra to treat ED in men. Sildenafil usually takes action within an hour. Like with other PDE5 inhibitors, you’ll only achieve an erection once sexually aroused.

How long it lasts

Viagra’s effects usually last about 4 hours but can last as long as 12 hours. It’s typically taken in doses between 25 to 100 milligrams (mg) per day.

Common side effects

Common side effects include:

• headaches;
• flushing;
• indigestion;
• nasal congestion;
• cold-like symptoms.

Cost

The exact price of sildenafil varies based on where you buy it. Brand-name Viagra often sells for more than $50. However, sildenafil has been sold under its generic name since 2017. Generic brands are often a fraction of the price.

Tadalafil (Cialis)

Tadalafil has been on the market since 2003 to treat ED. It usually takes effect within 20 minutes and should be taken at least half an hour before intercourse.

Tadalafil is also FDA-approved to treat benign prostate hyperplasia (BPH).

How long it lasts

Tadalafil has the longest action of any available PDE5 inhibitor at 24 to 36 hours. A typical daily dose varies from about 2.5 to 20 mg.

Common side effects

Common side effects include:

• headache;
• flushing;
• indigestion;
• nasal congestion;
• cold-like symptoms;
• back pain;
• muscle pain.

Cost

The cost of Cialis varies between pharmacies and depends on the strength of the medication. Larger 20-mg tablets cost upwards of $70. Like sildenafil, Cialis is also sold under its generic name (tadalafil) for a fraction of the price.

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Vardenafil (Levitra or Staxyn)

Vardenafil has been approved since 2003 for treating ED. It has the shortest onset of any PDE5 inhibitor and takes effect within 10 minutes.

How long it lasts

Vardenafil usually lasts for 5 to 7 hours but may last up to 12 hours. A typical dose of vardenafil is 5 to 20 mg per day.

Common side effects

Side effects include:

• headaches;
• flushing;
• indigestion;
• nasal congestion;
• cold-like symptoms.

Cost

Staxyn tends to be cheaper than Levitra, and you can expect to pay upward of $40 per tablet. Generic brands are also available.

Avanafil (Stendra)

Avanafil is the newest PDE5 inhibitor on the market and has been available since 2012. It generally takes effect within 30 to 45 minutes.

How long it lasts

Avanafil has a longer duration of effect than vardenafil and sildenafil but shorter than tadalafil with a half-life of around 5 hours. Avanafil is typically taken in a dose of 50 to 200 mg per day.

Common side effects

Common side effects include:

• headache;
• flushing;
• indigestion;
• nasal congestion;
• cold-like symptoms.

Cost

Stendra generally sells for more than $70 per 100-mg tablet, but prices fluctuate between pharmacies. There are currently no generic brands of avanafil available in the United States.

How do PDE5 inhibitors work?

PDE5 inhibitors have a vasodilating effect on the penis, meaning they help the blood vessels relax and increase blood flow.

The science behind an erection

The process of achieving an erection is complex. When you become sexually aroused, your parasympathetic nervous system becomes activated. This neural activity leads to a release of a molecule called nitric oxide (NO) that increases the production of another molecule called cyclic GMP.

Cyclic GMP relaxes the smooth muscles inside the blood vessels of your penis and increases blood flow by 20 to 40 times.

An enzyme called PDE5 breaks down cyclic GMP molecules and reverses the erection process. However, PDE5 inhibitors are similar in structure to cyclic GMP and bind to PDE5 to block this breakdown. This action enhances the action of NO and helps promote blood flow.

What about supplements?

PDE5 inhibitors naturally occur in some herbs. These herbs are often sold in supplement form and marketed to treat ED or enhance male vitality.

The FDA warns against dietary supplements for treating ED because many of these products contain undisclosed ingredients that may be harmful. The safety and effectiveness of these supplements also haven’t been adequately studied.

The takeaway

PDE5 inhibitors are a group of medications usually used to treat ED. These medications are effective for ED caused by physiological factors, such as poor circulation. However, they aren’t effective for treating ED caused by psychological factors, such as stress or anxiety.

For any additional questions, please get in touch with our experts and get consulted for free.