Tadalafil vs Sildenafil: Which ED treatment is right for you? 

DoktorABC editorial team

Accurate, up-to-date health information written by our editorial team and reviewed by UK-registered prescribers.

Key differences at a glance

Lets break down the key differences of the two medications, so we can understand where they differ, and what similarities exist between them. 

Sources: EMA Summary of Product Characteristics for sildenafil and tadalafil; NHS PrescQIPP bulletin on tadalafil once daily.

How tadalafil and sildenafil work

Both medicines belong to the same class of drugs: PDE5 inhibitors. Understanding the mechanism briefly helps explain both their effectiveness and their side effects.

During arousal, the body releases nitric oxide, which triggers the production of a chemical called cyclic GMP (cGMP). This relaxes the smooth muscle in the blood vessels of the penis, increasing blood flow and enabling an erection. PDE5 is an enzyme that breaks down cGMP, limiting the erection. Sildenafil and tadalafil both block PDE5, allowing cGMP to accumulate and sustain the blood flow needed for an erection.

Neither medicine creates an erection on its own. Sexual stimulation is still required. They simply make it easier for the body's natural response to arousal to work as it should.

The key pharmacological difference between the two medicines is selectivity. Tadalafil is highly selective for PDE5 over PDE6 (found in the retina) and PDE1 (found in vascular smooth muscle), which may contribute to a lower incidence of visual side effects compared to sildenafil. However, tadalafil does inhibit PDE11, found in skeletal muscle, which is thought to explain the back pain and muscle aches more commonly reported with tadalafil. 

Duration of efficacy: The most important practical difference

Duration of efficacy is where the two medicines diverge most significantly, and for most men it is the deciding factor.

Sildenafil has a quick onset of action of around 30 minutes after the initial dose, a duration of action of 4 to 6 hours, and a maximum duration of 12 hours. This means you need to plan around taking it. Many men find this works well when they know roughly when they are likely to be sexually active, but it can feel limiting if timing is unpredictable. 

Tadalafil has a half-life of approximately 17.5 hours, approximately four times longer than sildenafil. In practice, this means a single dose of tadalafil can support the ability to achieve an erection for up to 36 hours, which is why it is sometimes called the "weekend pill." You do not need to take it immediately before sexual activity, which removes much of the pressure around timing.

Neither medicine keeps you in a permanent state of arousal. The extended window of tadalafil simply means the drug remains present in the body at effective levels for longer, so an erection can occur in response to stimulation at any point within that window.

Dosage options

Sildenafil and tadalafil are available in different dose strengths, and tadalafil offers an additional daily dosing option that sildenafil does not. Understanding the options available helps you have a more informed conversation with your prescriber about what might work best for your circumstances.

Sildenafil

Sildenafil is available in three on-demand doses: 25 mg, 50 mg, and 100 mg. The standard starting dose for most men is 50 mg, taken approximately one hour before sexual activity. The dose can be increased to 100 mg or reduced to 25 mg depending on response and tolerability, under prescriber guidance. It should not be taken more than once in any 24-hour period.

Tadalafil

Tadalafil is available in two on-demand doses (10 mg and 20 mg) and two daily doses (2.5 mg and 5 mg). The on-demand dose is taken at least 30 minutes before sexual activity and can remain effective for up to 36 hours.

The daily dose option is a meaningful distinction. Taking 2.5 mg or 5 mg of tadalafil every day maintains a consistent level of the drug in the bloodstream, removing the need to plan around dosing at all. This is particularly appealing for men who have sex frequently, those who find the on-demand timing stressful, or those for whom spontaneity is important.

Food interactions: A practical consideration

The interactions with food are particularly relevant to daily life and require a pragmatic approach. 

Sildenafil's absorption is affected by food, particularly high-fat meals, which delay how quickly it is absorbed and can reduce peak blood levels. If you take sildenafil after a large dinner, it may take significantly longer to work, or feel less effective. For best results, it should be taken on an empty stomach or after a light meal. 

Conversely, tadalafil is not meaningfully affected by food. You can take it after a meal, with alcohol in moderation, or at any time without the same concern about reduced effectiveness. This makes it a more practical option for men who are likely to take it in the context of a meal out or a social occasion.

Side effect comparison

Because both medicines work through the same mechanism, their side effect profiles overlap significantly. The most common side effects of both include headache, facial flushing, nasal congestion, and indigestion.

The key differences are:

Sildenafil inhibits PDE6 in the retina more than tadalafil does, which is why some sildenafil users experience a bluish tinge to their vision or increased light sensitivity. Tadalafil inhibits PDE11 in skeletal muscle, which is thought to be responsible for the back pain and muscle aches more commonly associated with it.

Both medicines share the same serious contraindication: they must never be taken alongside nitrate medicines such as glyceryl trinitrate (GTN) spray or isosorbide mononitrate.

Because tadalafil has a longer half-life, side effects may last longer than those experienced with sildenafil. For most men this is a minor consideration, but it is worth bearing in mind.

Sildenafil vs Cialis: clarifying the confusion

This is a common source of confusion and worth addressing directly.

Cialis is simply the brand name for tadalafil, manufactured by Eli Lilly. Generic tadalafil contains exactly the same active ingredient at the same dose and has the same clinical effect. The same relationship exists between Viagra (the brand) and sildenafil (the generic).

Generic versions of both medicines have been available in the UK since 2013 (sildenafil) and 2018 (tadalafil), and both are significantly cheaper than their branded equivalents. There is no clinical reason to choose a branded version over a generic.

Which is better for whom?

Neither medicine is categorically better than the other. The right choice depends on your lifestyle, preferences, and individual response. The following is a practical guide, not a clinical recommendation; always discuss your specific circumstances with a prescriber.

Sildenafil may suit you better if:

• You have sex relatively infrequently and can plan around taking a tablet beforehand
• You prefer a shorter-acting medicine that clears your system more quickly
• Cost is a primary consideration (sildenafil is typically the cheaper of the two generics)
• You have tried tadalafil and experienced significant back pain or muscle aches

Tadalafil may suit you better if:

• Spontaneity is important to you and planning around a tablet feels stressful or disruptive
• You have sex frequently and would benefit from a daily low-dose option
• You regularly eat large meals or drink alcohol in the context of sexual activity, making food interactions a practical concern
• You experience visual side effects with sildenafil
• You also have symptoms of an enlarged prostate and would benefit from a single medicine addressing both

Price comparison in the UK

Both sildenafil and tadalafil are available as generics in the UK, which makes them considerably more affordable than their branded equivalents.

As a general guide:

• Generic sildenafil is typically the more affordable of the two and is the first-line prescribing choice on the NHS for most patients, on cost-effectiveness grounds
• Generic tadalafil is slightly more expensive but still accessible at reasonable cost from GPhC-registered private providers
• Daily tadalafil (2.5 mg or 5 mg) may work out cost-effectively for men who use it frequently, compared to on-demand dosing at higher strengths

Exact prices vary between providers. When comparing costs, always consider the total cost including consultation, dispensing, and delivery, not just the headline tablet price.

When to consult a prescriber

A medical assessment is required before starting either medicine for the first time. This is not a formality: it exists because both sildenafil and tadalafil interact with other medicines and can be contraindicated in certain cardiovascular conditions. A prescriber will review your medical history, current medications, and any underlying conditions before recommending the most appropriate option and dose.

You should also speak to your prescriber if:

• You have tried one medicine and found it ineffective or poorly tolerated
• You want to switch from one to the other
• You are considering moving from on-demand to daily tadalafil
• You experience any side effects that concern you
• Your circumstances change, such as starting a new medication that may interact

DoktorABC connects UK patients with licensed prescribers and GPhC-registered pharmacies, allowing you to complete a medical assessment and access treatment privately without a GP visit.

Final thoughts

Sildenafil and tadalafil are both effective, well-established treatments for erectile dysfunction. For most men, the choice comes down to two practical questions: how much do you value spontaneity, and how often are you likely to need the medication?

If you tend to plan ahead and have sex infrequently, sildenafil's shorter duration and lower cost make it a straightforward, effective option. If timing feels like pressure, or you would prefer not to think about it at all, tadalafil's extended window and daily dosing option offer a meaningfully different experience.

What neither medicine can do is work without arousal, work better at higher doses than prescribed, or be taken safely alongside nitrates. A consultation with a UK-registered prescriber is the best starting point for finding the right option for your circumstances.

FAQ

The DoktorABC medical advisory board

Dr. Roland Ruiken

Medical advisor, Norway

Dr. Viktor Simunovic

Medical advisor, Croatia

To the medical advisory board