PDE5 Inhibitors: Mechanism, Uses, and Side Effects

Published : Jun 05, 2024

Last Updated : Nov 21, 2024

PDE5 inhibitors are a class of medicines that block the degradation of cGMP in smooth muscle cells, promoting relaxation and healthy penile function. Drugs like Sildenafil, Tadalafil, and Vardenafil are widely recommended for treating erectile dysfunction (ED) and other issues like premature ejaculation. Their high effectiveness makes them the preferred choice for managing erectile function.

In this article, you will explore some of the well-known PDE5 inhibitors and find out how they work and other details about them.

Quick Intro: What are PDE-5 inhibitors?

PDE5 inhibitors target the enzyme Phosphodiesterase type-5, found in smooth muscles lining blood vessels, to improve blood flow necessary for erections. Initially developed for cardiovascular conditions, they are now widely used to treat erectile dysfunction (ED) and sometimes premature ejaculation.

Doctors prescribe PDE5 inhibitors based on patient needs. Still, they may be less effective for individuals with nerve or blood vessel damage, often caused by conditions like prostate surgery, cardiovascular disease, or diabetes. In such cases, other treatments may be required for ED management.

Where are PDE5 enzymes located?

PDE5 enzymes degrade cGMP and are distributed throughout the body, functioning in various tissues. They are found in the smooth muscle of the corpus cavernosum, skeletal muscle, cerebellar and pancreatic tissues, vascular and visceral smooth muscle, platelets, kidneys, and lungs.

How do PDE-5 inhibitors work?

PDE5 inhibitors improve blood flow to the penile area, essential for erections.

The enzyme cGMP relaxes and widens blood vessels, but in erectile dysfunction, PDE5 breaks down cGMP, restricting blood flow. PDE5 inhibitors block this enzyme, allowing cGMP to increase blood flow, resulting in firmer, improved erections.

PDE5 inhibitors are FDA-approved to treat the following conditions:

Erectile Dysfunction (ED): Widely used by men worldwide, PDE5 inhibitors effectively treat ED, helping achieve and sustain erections.
Benign Prostatic Hyperplasia (BPH): These drugs address prostate gland enlargement, which causes urination problems, affecting 70% of US males in their 60s.
Pulmonary Hypertension (PH): Certain PDE5 inhibitors treat PH, a severe condition involving high blood pressure in lung arteries. Symptoms include shortness of breath, chest pain, rapid heartbeat, and fatigue, requiring early treatment.

How do you take PDE5 inhibitors?

Take PDE5 inhibitors like Viagra, Cialis and Levitra as directed, 30-60 minutes before sex. Don’t take more than one in 24 hours. While Cialis has a daily low-dose option, high-fat meals can delay Viagra and Levitra. It can be taken with or without food, but limit alcohol to avoid reduced efficacy or side effects. Don’t take PDE5 inhibitors with nitrates or certain blood pressure meds. Always consult your doctor for the correct dose and instructions so it’s safe and effective.

What is the Best PDE5 inhibitor?

PDE5 inhibitors, introduced in the late 1990s, are effective prescription drugs for treating erectile dysfunction (ED), benign prostatic hyperplasia (BPH), and pulmonary hypertension.

Below, we have listed the best PDE5 inhibitors available in the market:

Viagra

Viagra, the first FDA-approved PDE5 inhibitor for erectile dysfunction (ED), remains the leading ED medication. Viagra dosage are available in 25mg to 100mg tablets; it should be taken 30 minutes to 4 hours before sexual activity. Effects typically begin within 30 minutes to 1 hour and last 4 to 5 hours. Viagra requires sexual stimulation to work and is available as both a brand name and a lower-cost generic option(Generic Viagra).

Revatio

Revatio, containing Sildenafil, is approved to treat pulmonary arterial hypertension (PAH), a condition causing high blood pressure in vessels connecting the heart and lungs. While Revatio and Viagra share the same active ingredient, they are not identical.

The typical adult dose is 20mg, up to 80mg, thrice daily. Revatio is the only approved PDE5 inhibitor for children, with dosage based on body weight. Generic options offer a more affordable alternative.

Cialis

Cialis, with its generic Tadalafil, is FDA-approved to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BPH). It lasts longer than other PDE5 inhibitors and is ideal for daily use or spontaneous sexual activity.

Dosage Options:

Daily: 2mg to 5mg, once a day.
As Needed: 5mg to 20mg, taken 30 minutes before sexual activity, as Cialis lasts for 36 hours.

For BPH, the typical dose is 5mg daily, which can also address ED. Cialis is available as a brand name or generic at a lower cost. Its long-lasting effects make it a top choice for BPH and urinary symptom relief.

Adcirca

Adcirca, containing Tadalafil, treats pulmonary arterial hypertension (PAH) in adults by relaxing blood vessels between the heart and lungs. While it shares the same active ingredient as Cialis, the two are not identical.

Adcirca lasts longer than Revatio, requiring less frequent dosing. The typical dose is 40mg once daily, as brand-name and generic options.

Vardenafil

Vardenafil, an FDA-approved PDE5 inhibitor for erectile dysfunction, is available in generic form and under the brand names Levitra and Staxyn.

It comes as oral or orally disintegrating tablets for those with difficulty swallowing. Typical doses range from 5mg to 20mg, taken 1 hour before sexual activity.

Vardenafil works faster than Viagra and Cialis, starting within 15 minutes (with sexual arousal) and lasting about five hours.

Stendra

Stendra (Avanafil), a newer FDA-approved PDE5 inhibitor, treats erectile dysfunction and works faster than Sildenafil and Tadalafil.

Available in tablet form, its typical dosage ranges from 50mg to 200mg, taken 15 minutes before sexual activity. 100mg or higher doses act within 15 minutes, while 50mg takes about 30 minutes.

Stendra is only available as a brand-name medication.

What are the Side effects of PDE5 inhibitors?

PDE5 inhibitors are generally well-tolerated but may cause side effects, including:

Nasal congestion
Headaches
Dyspepsia
Facial flushing
Cold-like symptoms
Back or muscle pain

Consult a doctor if side effects persist or worsen.

What are the Precautions to take while using PDE5 inhibitors?

Consult a Doctor: Always get approval and use the prescribed dosage. Avoid doubling or exceeding the dose.
Avoid Nitrates: Do not combine PDE5 inhibitors with nitrates, as this can cause severe hypotension.
Medical Conditions: Inform your doctor about heart issues, kidney/liver disease, or high blood pressure before taking PDE5 inhibitors.
Monitor Blood Pressure: PDE5 inhibitors can lower blood pressure. Avoid combining them with alpha-blockers or blood pressure medications.
Diet: Avoid heavy, fatty meals before use, which may delay absorption and effects.
Grapefruit and Alcohol: Steer clear of grapefruit juice and alcohol to reduce side effects and ensure effectiveness.

Do you know?

PDE5 inhibitors were discovered in the late 1980s while researching treatments for angina, and sildenafil (Viagra) was approved in 1998 for erectile dysfunction, revolutionising ED treatment.

Summary

PDE5 inhibitors effectively treat conditions like ED, BPH, and pulmonary hypertension, but results vary by individual. The best option depends on your age and medical condition.

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