This guide compares sildenafil, tadalafil, vardenafil and avanafil on the factors that actually shape the choice, so you can have a useful conversation with a prescriber. It is based on the UK Summaries of Product Characteristics and NICE, and is general information rather than personal advice; the right option is an individual decision.
The four options at a glance
The UK has four licensed PDE5 inhibitor tablets for erectile dysfunction: sildenafil (the active ingredient in Viagra and Viagra Connect), tadalafil (Cialis), vardenafil (Levitra) and avanafil (Spedra) 1235.
All four work the same way: they block the PDE5 enzyme to support the blood-vessel relaxation that allows an erection during sexual arousal 1. None of them works without stimulation, and none increases desire 1.
So the comparison is not really about which works 'best' in the abstract, but about which practical profile suits your circumstances 4. The main differences are onset, duration and the effect of food 12.
Because the choice is individual, this guide explains those differences rather than ranking the medicines, since one option suiting better than another is common 4.
How fast they work
Avanafil (Spedra) is the fastest, often working within 15 to 30 minutes5. That makes it appealing for spontaneity 5.
Sildenafil is usually taken about an hour before sex, and vardenafil about 25 to 60 minutes before 13. Tadalafil on demand is taken at least 30 minutes before, though its long duration means precise timing matters less 2.
If quick, on-the-spot use matters most to you, avanafil's speed stands out; if you prefer not to time things at all, tadalafil's long window may suit better 52. Sildenafil and vardenafil sit between the two 13.
Onset is one of the clearest practical differences, and for many men it is a deciding factor 4.
How long they last
Tadalafil is the long-acting one: a single on-demand dose can remain effective for up to about 36 hours, which is why it is called the 'weekend pill' 2. It can also be taken as a low daily dose for spontaneity 2.
Sildenafil, vardenafil and avanafil last a few hours each, suiting planned or on-demand use rather than a long window 135. They are taken before anticipated activity rather than to cover a whole day 1.
Duration shapes how the medicine fits your life: a long window suits less planning and more spontaneity, while a shorter-acting option suits occasional, planned use 21. Neither is better in the abstract 4.
The trade-off with a long-acting medicine is that side effects, if they occur, can also last longer 2. That is worth weighing alongside the convenience 4.
Considering treatment for erectile dysfunction? You can start an assessment with a Cloud Pharmacy clinician, who will review your medical history and confirm whether treatment is appropriate.
The effect of food
Sildenafil is the most affected by food: a heavy, high-fat meal can delay how quickly it works 1. So it is often best taken on a relatively empty stomach 1.
Tadalafil's onset is not significantly affected by food, which adds to its flexibility 2. Avanafil is affected less than sildenafil, and vardenafil can also be slowed by a heavy, high-fat meal 53.
If you often want to use an ED medicine around meals or socialising, the food effect is worth factoring in 12. Tadalafil's food-independence is part of its appeal for spontaneity 2.
These food differences are small but real, and they can tip the choice for someone who eats out often or does not want to plan around meals 12.
Side effects and tolerability
All four share a broadly similar side-effect profile, because they work the same way: headache, flushing, indigestion and nasal congestion are the common ones 1235. Most are mild 1.
There are small differences in emphasis: tadalafil is more associated with back and muscle pain, and because it is long-acting its side effects can last longer 2. Vardenafil has specific heart-rhythm cautions a prescriber considers 3.
Individual tolerability varies, so one option may suit someone better than another, which is a common reason for switching between them 4. If side effects are troublesome, a prescriber can adjust the dose or option 14.
Across all four, the serious red flags are the same: an erection lasting more than four hours, or sudden vision or hearing loss, need emergency care 1.
The safety rules that apply to all four
Some rules apply equally to every PDE5 inhibitor 1. The most important is that none may be combined with nitrates (such as GTN), nicorandil or 'poppers', because the combination can cause a dangerous drop in blood pressure; this is an absolute contraindication for all of them 1.
All four need caution with alpha-blockers and with some other medicines, and all are assessed for heart health before prescribing 13. A prescriber needs your full medicine and health history whichever you choose 14.
And all four work only with sexual stimulation and are not aphrodisiacs 1. These shared rules mean the safety framework is the same across the group 1.
Our guides on nitrates and alpha-blockers cover the key interactions that apply to all four 1.
How to choose
Choosing comes down to your priorities: if speed matters most, avanafil; if you want a long window and spontaneity, tadalafil; if you want a well-established, flexible on-demand option, sildenafil or vardenafil 5213. There is no single best choice for everyone 4.
Frequency also matters: for frequent activity, a low daily dose of tadalafil may suit, while for occasional use an on-demand tablet is simpler 2. Tolerability and your health, including heart conditions and other medicines, shape suitability too 13.
It is also common to try one and switch if it does not suit; that is a normal part of finding the right option, not a failure 4. A prescriber can guide this 4.
So the practical step is an assessment, where a clinician helps you weigh speed, duration, food, frequency and your health to pick the option most likely to suit you 14.
Getting any of them safely
Whichever you choose, all four are prescription-only (aside from the over-the-counter sildenafil and tadalafil options sold after a pharmacist check), so they should be obtained through a registered pharmacy after a proper assessment 12.
The MHRA warns that fake ED medicines are common online, so avoid unregulated sellers; a legitimate supply always comes with an assessment 62. The assessment also checks whether the ED needs further investigation, since it can signal an underlying condition 24.
If you would like help choosing, you can start an assessment with a clinician, who can compare the options for your circumstances 12. The fact that there are four means a medicine can usually be found to suit you 4.
Needing an ED medicine is common and nothing to be embarrassed about, and a confidential assessment is a routine, sensible part of getting one safely 24.
Trying one and switching is normal
One thing worth emphasising is that trying one PDE5 inhibitor and switching to another if it does not suit is a completely normal part of finding the right option 4. It is not a sign of failure, and many men settle on a different medicine from the one they started with 4.
A medicine might not suit because it does not work well enough for you, because the timing or duration does not fit your life, or because of side effects 41. Any of these is a reasonable reason to try a different option, and a prescriber can guide the change 4.
Because all four work the same way but differ in their practical profiles, there is usually an option that fits, even if the first choice was not ideal 42. That is the advantage of having four to choose from 4.
So if your first ED medicine has not been right, do not assume none will work; a different profile, or a dose adjustment, often makes the difference 41.
ED as a signal worth investigating
Whichever PDE5 inhibitor you consider, persistent ED can be an early signal of an underlying condition such as diabetes, high blood pressure or heart disease, because the blood-vessel health behind erections overlaps with cardiovascular health 24.
Psychological factors, stress, sleep, alcohol and some medicines can also contribute, so an ED tablet treating the symptom does not remove the value of understanding why the ED is happening 24. The NHS encourages reviewing persistent ED 2.
This is why an assessment matters whichever option you choose: it is a chance to look at your wider health, not just to authorise a prescription 24. Symptom relief and a proper look at the cause work best together 2.
So the four options give flexibility in treating the symptom, while an assessment makes sure the bigger picture is not overlooked 24. That combination, choice of medicine plus a proper look at the cause, is what good ED care looks like, and it is why the route you go through matters as much as the tablet you pick 24. If you would like help choosing, an assessment lets a clinician match the option to you 12. With four to choose from, there is usually one that fits, and switching if the first does not suit is a normal part of finding it 4.
Frequently asked questions
What are the four PDE5 inhibitors?
Sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra) and avanafil (Spedra) 1235. They work the same way but differ in onset, duration and the effect of food 4.Which works fastest?
Avanafil (Spedra) is the fastest, often working within 15 to 30 minutes 5. Sildenafil and vardenafil act within about an hour, and tadalafil at least 30 minutes before, though its long duration makes timing matter less 132.Which lasts longest?
Tadalafil, with an on-demand dose effective for up to about 36 hours, the 'weekend pill' 2. Sildenafil, vardenafil and avanafil last a few hours each 135.Do they have different side effects?
They share a similar profile (headache, flushing, indigestion, nasal congestion), with tadalafil more associated with back and muscle pain and vardenafil having heart-rhythm cautions 123. Individual tolerability varies 4.Do the same safety rules apply to all four?
Yes. None may be combined with nitrates (an absolute contraindication for all), all need caution with alpha-blockers, all are assessed for heart health, and all work only with stimulation 13.How do I choose between them?
By your priorities: speed (avanafil), a long window (tadalafil), or a flexible on-demand option (sildenafil or vardenafil), plus frequency, food and your health 521. There is no single best choice, and switching if one does not suit is normal 4.Your next step
The UK has four licensed PDE5 inhibitor tablets for erectile dysfunction: sildenafil, tadalafil, vardenafil and avanafil. They work the same way, so the differences that matter are practical: avanafil acts fastest (15 to 30 minutes), tadalafil lasts longest (up to about 36 hours), and sildenafil and vardenafil sit in between, while food affects sildenafil most and tadalafil least. All work only with sexual stimulation, and none may ever be combined with nitrates.
The right choice is personal, shaped by how fast you want it to work, how long you want it to last, the effect of food, how often you anticipate sex, your tolerability and your health, including heart conditions and other medicines. Trying one and switching if it does not suit is normal. Get any of them only through a registered pharmacy after a proper assessment, which also checks whether the ED needs further investigation. If you would like help choosing, you can start an assessment with a Cloud Pharmacy clinician.
Disclaimer
This guide is for general information only and does not constitute medical advice, diagnosis or treatment. The information here describes general clinical context based on UK regulatory sources cited above; it is not a recommendation for any specific medicine or treatment, which can only be made by a prescriber following individual assessment.
If you are considering treatment, speak to your GP or pharmacist, or arrange a consultation with a Cloud Pharmacy clinician. Prescription-only medicines are issued only after clinical assessment and where appropriate.
If you experience side effects from any medicine, you can report them through the Yellow Card scheme at yellowcard.mhra.gov.uk.
References
- Viagra (sildenafil) SmPC (PDE5 inhibitor for ED; ~1 hour before sex; food can delay onset; common side effects; nitrates absolute contraindication; alpha-blocker caution; works only with stimulation; priapism >4h, vision/hearing loss)
- Cialis (tadalafil) SmPC (up to ~36-hour duration; on-demand and daily; food not significant; back/muscle pain; nitrates contraindication)
- Vardenafil SmPC (~25-60 min onset; range 5-20 mg; heart-rhythm cautions; nitrates contraindication)
- NICE CKS erectile dysfunction (PDE5 inhibitor class; no single best option; choice individual; switching common; assessment)
- Spedra (avanafil) SmPC (fastest onset ~15-30 min; usual 100 mg, range 50-200 mg; food effect less than sildenafil; nitrates contraindication)
- MHRA #FakeMeds (fake ED medicines common online; buy only from registered pharmacies)
