Phosphodiesterase-5 (PDE-5) inhibitors: Uses, Side Effects

Phosphodiesterase-5 (PDE-5) inhibitors: Uses, Side Effects
Published : Jun 05, 2024

PDE-5 inhibitors, or Phosphodiesterase-5 inhibitors, are a class of medicines that relax blood vessels and smooth muscles in different areas of the body. They are well-known for treating various medical conditions, such as erectile dysfunction. However, PDE-5 inhibitors can also treat pulmonary hypertension and benign prostatic hyperplasia.

What are PDE-5 inhibitors?

PDE5 inhibitors target PDE-5, an enzyme known as Phosphodiesterase type-5. This enzyme is present in the smooth muscles that line your blood vessels and is responsible for narrowing them. You need to know that PDE-5 inhibitors play a vital role in controlling blood flow, which is necessary for attaining an erection.

Primarily, PDE5 inhibitors were developed for cardiovascular conditions treatments such as chest pain and hypertension. Nowadays, PDE5 inhibitors are used across the world by men to treat erectile dysfunction disorder.

Apart from ED, some PDE-5 inhibitors are also effective in providing relief from premature ejaculation- which is another common form of male sexual dysfunction. Depending on patient preference and medical needs, a doctor advice the ideal dose of PDE5 Inhibitors for you.

But note that PDE5 inhibitors are not very effective in people who have sustained damage to the nerves or blood vessels of the penis. Especially people with conditions like prostate surgery, cardiovascular disease, and diabetes can have nerve damage. These complications can make it harder for PDE5 inhibitors to work effectively, such as you might need other surgical methods to get effective management for ED.

Types of PDE-5 inhibitors

The first PDE5 inhibitors were introduced in the late 1990s due to their effectiveness in treating certain conditions in clinical trials. Nowadays, several PDE5 inhibitors are available as prescription drugs for treating ED, benign prostatic hyperplasia, and pulmonary hypertension.

In this article, you will learn about the different types of PDE-5 inhibitors:


The FDA approves Viagra and its generic Sildenafil to treat erectile dysfunction. The first PDE-5 inhibitor approved for ED was Viagra, which is still the number one ED medicine today. It is available in tablet form.

Viagra dose ranges from 25mg to 100mg and should be taken 30 minutes to 4 hours before planned sexual activity. You can experience the effects of this medicine within 30 minutes to 01 hours after administration. At the same time, Viagra’s effect might last in the body for 4 to 5 hours. To let Viagra or other PDE5 Inhibitors work for you, you need sexual stimulation on your own to improve your erectile function. You can find Viagra in the market as a brand-name medicine and a lower-cost generic.


Revatio and its generic, Sildenafil, are approved medications for treating pulmonary arterial hypertension (PAH). PAH leads to high blood pressure in the blood vessels that carry blood from the heart to the lungs. You should know that Revatio and Viagra both contain Sildenafil, but they are not identical.

For PAH, the typical dose of Revatio for adults is 20mg, and the maximum dose is 80mg, three times a day. To treat pulmonary arterial hypertension in children, Revatio is the only approved PDE-5 inhibitor. The dosage of this medicine for children depends on their body weight. By choosing the lower-cost generic, you can avail the best price for Revatio.


Cialis and its generic, Tadalafil, are FDA-approved to treat erectile dysfunction and benign prostatic hyperplasia (BPH). Compared to other PDE-5 inhibitors, the Cialis pill lasts longer in the body.

You can take this medicine every day for treating ED instead of as required before sexual activity. People who love to indulge in spontaneous sexual intercourse can take Cialis as it is the most suitable option for them. Cialis is available in tablet form. The typical dosage of Cialis for ED depends on whether you have been recommended to take it daily or as medical needs:

Daily: Cialis daily dosage is available from 2mg to 5mg, once a day

As required: Cialis as the required dosage is available from 5mg to 20mg, taken 30 minutes before the sexual activity.

The effects of Cialis, as needed, last for 36 hours, giving you enough time to meet all your sexual desires. For BPH, the average Cialis dose is 5mg once a day. A 5mg dose is best if you take Cialis to treat BPH and ED conditions. Due to its long-lasting effects, Tadalafil is among the best choice for BPH to lower urinary tract symptoms.

You can find both Cialis as a brand-name medicine and a lower-cost generic at licensed pharmacies.


Adcirca and its generic Tadalafil are effective in treating PAH in adults. It works like Revatio by relaxing the blood vessels from the heart to the lungs. Both Cialis and Adcirca contain Tadalafil, but they are not identical.

When compared to the Revatio pill, Adcirca is taken less frequently because its effects last longer in the body. The typical dose of Adcirca is 40mg once a day. You can find Adcirca as brand-name and generic.


Vardenafil is another PDE5 inhibitor approved by the FDA for improving erectile function during ED. Although generic versions of Vardenafil are only available nowadays, it was also available under the brand names Levitra and Staxyn.

Vardenafil is available in oral tablet form. However, if you have a problem swallowing the pills, you can take an orally disintegrating tablet. The typical dose of Vardenafil ranges from 5mg to 20mg, taken 1 hour before the sexual activity.

When compared to Viagra and Cialis, Vardenafil works faster. It starts to work fast within 15 minutes but can take one hour under your sexual arousal. However, its effects last for 5 hours. 


Stendra (Avanafil) is the new PDE5 inhibitor approved by the FDA to treat erectile dysfunction in men. When compared to Sildenafil and Tadalafil, Stendra works faster. It is available in tablet form.

The typical Stendra dosage is 50mg to 200mg and should be taken almost 15 minutes before sexual intercourse. Dosages that are 100mg or higher start to work within 15 minutes. However, the 50mg Stendra dose starts to work within 30 minutes.

Unlike other PDE5 inhibitors for ED, Stendra is available only as a brand-name medicine.

How do PDE-5 inhibitors work?

To achieve an erection, men require an excellent and smooth flow of blood in the penile area. An enzyme called cGMP helps relax and widen blood vessel muscle to allow good blood flow.

During erectile dysfunction, another enzyme known as PDE5 breaks down cGMP because proper blood flow into the male sexual organ is blocked.  

The primary role of PDE5 inhibitors is to decrease the action of the PDE5 enzyme. Once the action of PDE5 is inhibited or decreased by the PDE5 inhibitors, cGMP enables increased blood flow to the male sexual organ, further resulting in stiffer and better erections.

Uses of PDE-5 inhibitors

Though PDE-5 inhibitors have several uses, currently, the US Food and Drug Administration has approved PDE5 inhibitors to treat the following medical conditions:

Erectile dysfunction

PDE5 inhibitors are highly effective in treating erectile dysfunction problems in men. When a man is unable to achieve or sustain a hard erection for sexual activity, he has erectile dysfunction. Several men across the world use PDE5 inhibitor medicines to treat ED.

Benign prostatic hyperplasia (BPH)

Benign prostatic hyperplasia, or BPH, is a disorder that leads to enlargement of the prostate gland. This further causes problems in urination. This condition affects 70% of males in the United States in their 60s.

Pulmonary hypertension (PH)

Some types of PDE5 inhibitors are effective at treating a condition called pulmonary hypertension. PH or pulmonary hypertension is a form of high blood pressure that affects arteries in your lungs. PH may include life-threatening risk factors for a person and must be addressed at the earlier stages.

Some common symptoms of pulmonary hypertension include shortness of breath, fast heart rate, chest pain, and tiredness.

Side effects of PDE5 inhibitors

When used as recommended by the doctor, PDE5 inhibitors are easily tolerated by the body. However, like other medicines, they can sometimes cause side effects.

Some common side effects of PDE5 inhibitors include:

  • Nasal congestion

  • Headaches

  • Dyspepsia

  • Facial flushing

  • Cold-like symptoms

  • Back or muscle pain

It is essential to consult a doctor immediately if you find that any adverse effects persist or worsen.

Precautions to take while using PDE5 inhibitors:

Follow the below-listed precautions while taking any of the above-given PDE5 inhibitors:

Consult a healthcare professional: Before you use any PDE5 Inhibitors, make sure your doctor approves them for you. Use them in the prescribed dosage, and avoid doubling the dose or taking a higher dose than the recommended one.

Avoid Nitrates: If you are taking medicines like Nitrates, avoid taking any PDE5 Inhibitor with it. Drug interactions among these medicines can lead to the risk of severe hypotension.

Certain medical conditions: If you have any medical problems other than ED, you must be cautious. For example, suppose you have heart problems like heart failure, a heart attack or stroke, kidney or liver disease, or high blood pressure. In that case, you must inform your doctor about your medical condition and take medicine accordingly as prescribed.

Blood Pressure: Monitor your blood pressure, as PDE5 inhibitors can cause hypotension. Avoid taking PDE5 inhibitors with alpha-blockers and other drugs used to treat high blood pressure.

Diet: Using PDE5 Inhibitors after heavy, fatty meals may delay their rate of absorption. In such a case, this anti-ED drug might take a little longer to kick in.

Avoid Grapefruit and Alcohol: Avoid using grapefruit juice and alcohol while using PDE5 Inhibitors. Combined use of these substances can increase the risk of side effects and may impair the ability to get erections.


Therefore, PDE5 inhibitors are effective in treating various medical conditions, but their results differ from person to person. The right option for you will depend on your age and the condition that needs to be treated.

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