PDE-5 Inhibitors

PDE-5 inhibitors are medications that are prescribed to men who suffer from erectile dysfunction. They are usually taken orally, although other forms, such as creams, are also available.

  1. Treat erectile dysfunction.
  2. Various types available, including Viagra and Cialis.
  3. Increase blood flow to the penis. 

If you have any concerns relating to erectile dysfunction, you can speak with one of our GPhC-registered clinicians by using our online video consultation service. Our clinicians are available for appointments between 9.30am-4.30pm, Monday to Friday. 

  • UK prescribers
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Product information

What are PDE-5 inhibitors?

PDE-5 inhibitors are medications that are prescribed to treat erectile dysfunction. The most well-known of these are Viagra (sildenafil) and Cialis (tadalafil). They are available in different forms, although oral tablets are the most common. They work by allowing blood to flow more freely to the penis, helping to trigger and maintain erections during sexual activity.

What is erectile dysfunction?

Erectile dysfunction (ED) which is also known as impotence, is a common condition in the UK and globally. It’s most common in men over the age of 40. Although any man can experience it at any point in their lives, if it continues to present over a long period of time it may be due to emotional or physical issues that will need to be addressed. 

What symptoms can erectile dysfunction cause?

Symptoms of erectile dysfunction include being unable to achieve or maintain an erection, despite sexual activity. The most common causes are consumption of alcohol, stress, fatigue and anxiety. The chances of it occurring are also increased if you are a smoker, have an unhealthy diet or do not get enough exercise.

How is erectile dysfunction diagnosed?

Your GP can offer advice and medication and, where necessary, they may recommend that you visit a sexual health clinic. Most sexual health clinics do not require an appointment. 

During your assessment at the clinic, you will be asked about your lifestyle, including your relationship status. Your prescribing doctor will also take blood tests and examine your genitals in order to rule out any physical issues that may be causing the problem.

How is erectile dysfunction treated?

Treatment for erectile dysfunction depends on what’s triggering it. If the cause is physical in nature, it will require specific treatment. For example, hormonal issues are treated with hormone replacement therapy, while high blood pressure, which can narrow the blood vessels and prevent you from achieving an erection, can be treated with statins to lower cholesterol or various medications to help lower blood pressure.

If psychological problems are triggering ED, such as anxiety, your prescribing clinician may recommend a talking therapy, such as cognitive behavioural therapy (CBT). Emotional distress may require psychotherapy. 

Medication for ED has improved significantly over the last few decades, and there are now many different types of PDE-5 inhibitors available. The most common treatments are sildenafil (Viagra), tadalafil (Cialis) avanafil (Spedra) and vardenafil (Levitra). Viagra Connect is also available, and can be purchased over the counter. Other treatments include alprostadil (Caverject) and a combination of aviptadil and phentolamine mesilate (Invicorp). 

ED can be well managed with medication, and with so many different treatments available, the vast majority of men can find a suitable medication without experiencing any major side effects. 

If you would like to discuss ED and treatment for the condition with one of our registered clinicians, you can book an appointment with one of them via our online video consultation service, between 9.30am-4.30pm, five days a week. Our clinicians can also provide referrals to specialists for treatment and fit notes, where suitable. 

Page last reviewed:  20/07/2020
Side effects and warnings

What side effects can PDE-5 inhibitors cause? 

All medications come with some risk of side effects, and you should be aware of specific side effects for your treatment prior to use. You can discuss any potential side effects with your prescribing clinician, and refer to the patient information leaflet that comes with your treatment for details.

Because there are many different forms of PDE-5 inhibitors, the following information may not be accurate for your specific treatment. 

The following side effects relate to tadalafil (Cialis). You should discontinue use and seek medical attention immediately if you experience: allergic reactions; chest pain (do not use nitrates); priapism; a prolonged and possibly painful erection which lasts for more than 4 hours; sudden loss of vision; sudden reduction in or loss of hearing.  

Other side effects include: 

Common (between 1 and 10 patients): headaches, back pain, muscle aches, discomfort in the limbs, flushing, blocked nose and indigestion.

Uncommon (1-10 in every 1,000 patients): giddiness, stomach pain, nausea, vomiting, acid reflux, sight problems, pain in the eyes, problems breathing, blood in the urine, prolonged erection, thumping heartbeat, rapid heartbeat, hypertension, decreased blood pressure, nose bleeds, tinnitus, swollen hands or feet and fatigue. 

Rare (1-10 in every 10,000 patients): loss of consciousness, fits, memory problems, swelling of the lids of the eyes, reddened eyes, sudden loss of hearing, severe rash, blood from the penis, traces of blood in semen and sweating. 

The following side effects have also been reported but were not seen in trials: migraines, swelling, allergic reactions, rashes, affected blood flow to the eyes, palpitations, angina and sudden cardiac death. 

Can PDE-5 inhibitors interact with other medications? 

If you are currently or have recently taken any other medications, you should inform your doctor before starting treatment. Because all drugs have the potential to interact with others, this is the only way in which your prescribing clinician can provide you with safe treatment.  

The following information relates to tadalafil: you should avoid using tadalafil if you are taking nitrates. 

The following medications may affect how well tadalafil works and your doctor may consider an alternative treatment: alpha blockers, medicines to treat high blood pressure, alpha reductase inhibitors, ketoconazole tablets, protease inhibitors, phenobarbital, phenytoin, carbamazepine, rifampicin, erythromycin, clarithromycin, itraconazole and other treatments for erectile dysfunction.

Warnings and precautions when using PDE-5 inhibitors 

If you have any health issues, it’s important that you tell your prescribing clinician before they issue you with PDE-5 inhibitors. This includes any conditions that you are prone to.

It’s particularly important that you make your prescribing doctor aware of any of the following conditions: sickle cell anaemia, multiple myeloma, deformations of the penis, serious liver problems and severe kidney problems.

Tadalafil may not be effective if you have had pelvic surgery or part or all of your prostate gland removed.

What types of PDE-5 inhibitors are available?

There are many different types of PDE-5 inhibitors available in a variety of forms. Typically, PDE-5 inhibitors are tablets that are swallowed with water, but there are also creams and orodispersible (treatments that melt in the mouth) tablets that you can use. 

Some PDE-5 inhibitors may be available as sprays or suppositories.

Popular examples of PDE-5 inhibitors include sildenafil (Viagra), tadalafil (Cialis), avanafil (Spedra) and vardenafil (Levitra). 

Is it safe to take PDE-5 inhibitors if you are pregnant? 

PDE-5 inhibitors are suitable for men only. If you are a woman and are having sexual health issues, there are many sexual health clinics available that you can attend without having made an appointment. You can also book an appointment to see your GP.

Page last reviewed:  20/07/2020
Questions and Answers

Is it safe to drink alcohol whilst taking PDE-5 inhibitors?

Because alcohol can lower your blood pressure, you should only consume it in moderation whilst taking PDE-5 inhibitors, as it can lead to dizziness. 

Can PDE-5 inhibitors affect your ability to drive? 

While the risk of dizziness whilst taking PDE-5 inhibitors is not high, it has been reported, so it’s important that you understand how this medication affects you before operating any heavy machinery.

Can PDE-5 inhibitors cause allergic reactions? 

Allergic reactions to PDE-5 inhibitors are rare, but they can occur. If you are aware of any allergies you have, it’s essential that you tell your prescribing clinician before starting treatment. You can also refer to the patient information leaflet that comes with your medication, which lists the ingredients in the treatment. 

Can I buy PDE-5 inhibitors over the counter? 

The only PDE-5 inhibitor currently available to buy over the counter is Viagra Connect. All other PDE-5 inhibitors are available on prescription only.  

How can I buy PDE-5 inhibitors online?

You can discuss PDE-5 inhibitors and erectile dysfunction with one of our GMC-registered clinicians via our online video consultation service. They are available from 9.30am-4.30pm, Monday to Friday. They can also issue fit notes and referrals to specialists for treatment, where appropriate. 

Page last reviewed:  20/07/2020

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