Avanafil Diarrhoea: Causes, Duration & What to Do

Avanafil and Diarrhoea: What You Need to Know

Published: 15 November 2026

Avanafil diarrhoea is an uncommon side effect that affects a small proportion of men taking this erectile dysfunction medicine, which is sold under the brand name Spedra in the UK. Most people tolerate avanafil well, but understanding why diarrhoea can occur and how to manage it can help you feel more confident about your treatment. This page explains how common the side effect is, what causes it, how long it typically lasts, and when you might want to consider an alternative ED medicine.

How Common Is Avanafil Diarrhoea?

Diarrhoea is classified as an uncommon side effect of avanafil, meaning it affects fewer than 1 in 100 men who take the medicine [6]. This makes it much less frequent than the more commonly reported side effects such as headache or flushing, which occur in around 1 in 10 men. Clinical trials of avanafil have shown that gastrointestinal symptoms, including diarrhoea, nausea, and indigestion, are generally mild when they do occur [11].

The likelihood of experiencing diarrhoea does not appear to increase significantly with higher doses of avanafil, though individual responses vary. Most men who take Spedra (the branded form of avanafil) do not report any digestive upset at all. If you do notice loose stools or diarrhoea after taking avanafil, it is worth keeping a record of when it happens and how severe it is, as this information can help your prescriber decide whether to adjust your dose or suggest a different treatment.

It is also important to distinguish between diarrhoea caused by the medicine itself and diarrhoea that might be due to other factors, such as anxiety about sexual performance, dietary changes, or an unrelated stomach bug. If you experience diarrhoea only occasionally and it resolves quickly, it may not be directly linked to avanafil. However, if it occurs consistently after taking the medicine, it is more likely to be a side effect.

Why Does Avanafil Cause Diarrhoea?

Avanafil belongs to a class of medicines called PDE5 inhibitors, which work by relaxing smooth muscle in blood vessels to improve blood flow to the penis during sexual stimulation [6]. However, PDE5 enzymes are not only found in the blood vessels of the penis; they are also present in other parts of the body, including the gastrointestinal tract. When avanafil inhibits PDE5 in the gut, it can sometimes affect the normal movement and function of the digestive system, leading to symptoms such as diarrhoea or loose stools.

Another possible reason is that PDE5 inhibitors can cause a slight drop in blood pressure, which may indirectly affect gut motility in some individuals. Additionally, some men may experience a degree of nervousness or anticipation before sexual activity, and this psychological response can also contribute to digestive upset. The combination of these factors means that diarrhoea, when it does occur, is usually the result of the medicine's broader effects on smooth muscle and blood flow rather than a direct toxic effect on the stomach or intestines.

It is worth noting that avanafil is generally well tolerated and has a relatively short duration of action compared to some other PDE5 inhibitors, which may reduce the overall exposure to side effects. If you are taking other medicines or have underlying digestive conditions, these can also influence how your body responds to avanafil.

Individual Variation in Response

Not everyone who takes avanafil will experience diarrhoea, and the severity can vary widely. Some men may notice only a single episode of loose stools, while others might experience more persistent symptoms. Factors such as your overall health, diet, hydration status, and whether you take the medicine on an empty stomach or with food can all play a role. If you find that diarrhoea is a recurring problem, it may be helpful to experiment with the timing of your dose or to take it with a light meal, though you should discuss any changes with your prescriber first.

How Long Does Avanafil Diarrhoea Last?

For most men who experience diarrhoea after taking avanafil, the symptom is short-lived and resolves within a few hours. Avanafil has a relatively rapid onset of action, typically working within 15 to 30 minutes, and its effects usually last for around four to six hours [6]. Because the medicine is cleared from the body fairly quickly, any side effects, including diarrhoea, tend to be temporary and should not persist beyond the period when the drug is active in your system.

If you notice that diarrhoea continues for more than 24 hours after taking avanafil, or if it is severe and accompanied by other symptoms such as abdominal pain, fever, or blood in your stools, it is important to seek medical advice. Prolonged or severe diarrhoea can lead to dehydration and may indicate an unrelated condition that requires investigation. In most cases, however, the symptom is mild and self-limiting, meaning it goes away on its own without the need for specific treatment.

Some men find that their body adjusts to avanafil over time, and side effects that were noticeable during the first few doses become less troublesome with continued use. If you are new to avanafil and experience diarrhoea, it may be worth giving your body a chance to adapt before deciding to switch to a different medicine. However, if the symptom is distressing or interferes with your quality of life, there are other effective ED treatments available that may suit you better.

Self-Care Tips for Managing Avanafil Diarrhoea

If you experience mild diarrhoea after taking avanafil, there are several practical steps you can take to manage the symptom and reduce discomfort. Staying well hydrated is the most important measure, as diarrhoea can lead to fluid loss. Drink plenty of water throughout the day, and consider using oral rehydration solutions if you feel dehydrated. Avoid alcohol and caffeine, as these can worsen dehydration and may also interact with the blood-pressure-lowering effects of avanafil.

Eating a bland, low-fibre diet for a day or two can help settle your stomach. Foods such as plain rice, toast, bananas, and boiled potatoes are gentle on the digestive system. Avoid spicy, fatty, or heavily processed foods, as these can aggravate diarrhoea. Some men find that taking avanafil with a light meal, rather than on an empty stomach, reduces the likelihood of gastrointestinal upset, though this may slightly delay the onset of the medicine's effect.

Over-the-counter anti-diarrhoeal medicines, such as loperamide, can be used to manage symptoms if needed, but you should not rely on them regularly without speaking to a healthcare professional. If diarrhoea is a recurring problem, it is worth keeping a diary of what you eat and drink around the time you take avanafil, as this may help identify any dietary triggers. Remember that stress and anxiety can also affect your digestive system, so relaxation techniques and open communication with your partner may help reduce overall symptoms.

When to Adjust Your Dose

Avanafil is available in three strengths: 50 mg, 100 mg, and 200 mg. If you are taking a higher dose and experiencing troublesome diarrhoea, your prescriber may suggest trying a lower dose to see if this reduces side effects while still providing the benefit you need. Conversely, if you are on a low dose and not experiencing significant side effects, there is no need to increase the dose unless your erectile function is not improving. Any dose adjustment should always be discussed with your prescriber during your online consultation or follow-up.

When to Seek Medical Help for Avanafil Diarrhoea

While mild, short-lived diarrhoea is usually not a cause for concern, there are certain situations where you should seek medical advice. If diarrhoea is severe, persistent (lasting more than 24 hours), or accompanied by symptoms such as high fever, severe abdominal pain, blood or mucus in your stools, or signs of dehydration (such as dizziness, dark urine, or a dry mouth), you should contact your GP or call NHS 111 for guidance. These symptoms may indicate a more serious condition that is unrelated to avanafil and requires prompt investigation.

You should also seek help if you experience any signs of an allergic reaction, such as a rash, swelling of the face or throat, or difficulty breathing, although these are very rare with avanafil. If you have any concerns about whether your symptoms are normal or if they are affecting your daily life, it is always better to speak to a healthcare professional rather than trying to manage the problem on your own.

If diarrhoea is mild but persistent and you feel it is affecting your confidence or willingness to use avanafil, discuss this with your prescriber. They can review your treatment and may suggest switching to a different PDE5 inhibitor, such as sildenafil or tadalafil, which have slightly different side-effect profiles and may be better tolerated. Remember that erectile dysfunction is common and treatable, and there are several effective options available, so you do not have to put up with side effects that are troublesome to you [1][2].

Alternatives to Avanafil If Diarrhoea Persists

If you find that diarrhoea continues to be a problem with avanafil, or if it is severe enough to discourage you from using the medicine, there are other effective treatments for erectile dysfunction that you can consider. All licensed oral ED medicines in the UK are PDE5 inhibitors, but they differ in their onset of action, duration, and side-effect profiles, so switching to a different one may help [3][4][5].

Sildenafil (the generic form of Viagra) is a well-established option that typically takes effect within about an hour and lasts for around four to five hours. Tadalafil (the generic form of Cialis) has a longer duration of action, with effects lasting up to 36 hours, which can offer more spontaneity. Tadalafil is also available as a low-dose daily tablet, which some men prefer as it allows for sexual activity at any time without the need to plan ahead. Vardenafil (the generic form of Levitra) is another alternative that works in a similar way to sildenafil and avanafil. Each of these medicines can cause side effects, but the specific symptoms and their severity vary from person to person.

At Cured Pharmacy, all prescription ED medicines are supplied following an online consultation reviewed by a UK-registered prescriber, who will take into account your medical history, current medicines, and any side effects you have experienced. If you have tried avanafil and found it unsuitable, your prescriber can help you find an alternative that is more comfortable for you. It is important not to stop or change your treatment without professional advice, as your prescriber needs to ensure that any new medicine is safe and appropriate for you.

Non-Oral Treatments

If oral PDE5 inhibitors are not suitable or well tolerated, there are other treatment options available. Eroxon is a topical gel medical device that can be purchased without a prescription and works by creating a cooling and warming sensation to stimulate blood flow. Vitaros is a prescription alprostadil cream applied to the tip of the penis, and Caverject is an alprostadil injection [7]. These alternatives work differently from PDE5 inhibitors and may be worth discussing with your GP or a specialist if oral medicines continue to cause troublesome side effects.

Scientific References

1. NHS. (n.d.). Erectile dysfunction (impotence). NHS website. https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ [accessed 15 November 2026]
2. National Institute for Health and Care Excellence. (n.d.). Erectile dysfunction. Clinical Knowledge Summaries. https://cks.nice.org.uk/topics/erectile-dysfunction/ [accessed 15 November 2026]
3. Joint Formulary Committee. (n.d.). Sildenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/sildenafil/ [accessed 15 November 2026]
4. Joint Formulary Committee. (n.d.). Tadalafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/tadalafil/ [accessed 15 November 2026]
5. Joint Formulary Committee. (n.d.). Vardenafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/vardenafil/ [accessed 15 November 2026]
6. Joint Formulary Committee. (n.d.). Avanafil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/avanafil/ [accessed 15 November 2026]
7. Joint Formulary Committee. (n.d.). Alprostadil. British National Formulary. NICE. https://bnf.nice.org.uk/drugs/alprostadil/ [accessed 15 November 2026]
8. National Institute for Health and Care Excellence. (2014). Erectile dysfunction: avanafil (ESNM45). https://www.nice.org.uk/advice/esnm45 [accessed 15 November 2026]

Information on this page is for educational purposes only and is not medical advice. Prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting or changing any medication.