Sildenafil and tadalafil are two widely used medicines for erectile dysfunction (ED). Both belong to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors, but they differ considerably in how long they remain active, how they are normally taken and how food may affect them.
This guide compares sildenafil and tadalafil so that the main practical differences are easier to understand. It is intended as general educational information and does not replace advice from a doctor or pharmacist.
Sildenafil vs tadalafil at a glance
| Feature | Sildenafil | Tadalafil |
|---|---|---|
| Medicine type | PDE5 inhibitor | PDE5 inhibitor |
| Used for erectile dysfunction | Yes | Yes |
| Typical timing before sexual activity | Approximately 1 hour | From approximately 30 minutes |
| Duration | Shorter acting | Effects may last up to 36 hours |
| Food effect | A meal, particularly a large or high-fat meal, can delay absorption | Absorption is not significantly affected by food |
| Daily treatment option | Not normally used as a once-daily ED treatment | Lower-dose daily treatment may be prescribed for suitable patients |
| Sexual stimulation required | Yes | Yes |
How do sildenafil and tadalafil work?
Both medicines inhibit the PDE5 enzyme. This helps blood vessels in the penis relax and allows increased blood flow when a person is sexually stimulated.
Neither medicine automatically produces an erection. Sexual stimulation is still necessary for the medicine to have its intended effect.
You can read more about the individual medicines in our Sildenafil Guide and Tadalafil Guide.
What is the main difference between sildenafil and tadalafil?
The most noticeable difference is the length of time for which the medicines can remain effective.
Sildenafil is generally used as an on-demand treatment before anticipated sexual activity. Tadalafil is longer acting and may remain effective for up to 36 hours after a dose.
This does not mean that tadalafil causes an erection for 36 hours. It means that during this period the medicine may make it easier to achieve an erection in response to sexual stimulation.
How quickly do they work?
Sildenafil
Sildenafil is commonly taken approximately one hour before sexual activity. The actual time before an individual notices an effect can vary.
Taking sildenafil with food can slow its absorption. A large or high-fat meal may therefore make the medicine take longer to have an effect than when it is taken in the fasted state.
Tadalafil
Tadalafil may be taken from around 30 minutes before anticipated sexual activity. Because it remains active considerably longer than sildenafil, the exact timing of sexual activity is generally less restricted by the dosing window.
Tadalafil can be taken with or without food because food does not have a clinically significant effect on its absorption.
Which lasts longer: sildenafil or tadalafil?
Tadalafil is the longer-acting medicine.
Its effects may remain available for up to 36 hours. This longer duration is one of the principal differences between tadalafil and sildenafil.
Sildenafil has a shorter treatment window and is therefore more closely associated with taking a dose in advance of anticipated sexual activity.
Longer duration does not necessarily mean that one medicine is more effective than the other. The most appropriate treatment depends on individual circumstances, health, other medicines and advice from a healthcare professional.
Does food affect sildenafil and tadalafil differently?
Yes. This is another important practical difference.
The absorption of sildenafil may be delayed when it is taken with food. This is particularly relevant after a substantial meal, when a person may notice that the medicine appears to take longer to work.
Tadalafil absorption is not significantly affected by food. It can therefore generally be taken with or without a meal.
Anyone experiencing inconsistent effects should not automatically increase the dose. Factors such as meal timing, alcohol, other medicines, health conditions and incorrect use should first be considered with a doctor or pharmacist.
Can tadalafil be taken every day?
Tadalafil has both on-demand and lower-dose daily treatment regimens.
For some people who anticipate frequent sexual activity, a healthcare professional may consider a once-daily lower dose appropriate. Daily treatment maintains a more consistent level of tadalafil in the body rather than requiring a larger on-demand dose before sexual activity.
Tadalafil 10 mg and 20 mg are generally intended for use before anticipated sexual activity rather than continuous daily use.
The appropriate dose and treatment schedule should be determined by a healthcare professional.
What side effects can occur?
Like all medicines, sildenafil and tadalafil can cause side effects, although not everyone experiences them.
Possible effects associated with PDE5 inhibitors can include:
- headache
- facial flushing
- indigestion
- nasal congestion
- dizziness
The side-effect profiles are not identical. Individual reactions also vary, so a medicine tolerated well by one person may not be as suitable for another.
Persistent or troublesome side effects should be discussed with a doctor or pharmacist.
Sildenafil, tadalafil and nitrate medicines
A particularly important safety issue concerns nitrate medicines used for conditions such as angina.
Sildenafil and tadalafil should not be combined with nitrates because the combination can cause a potentially dangerous fall in blood pressure.
This includes medicines such as glyceryl trinitrate (GTN). Recreational nitrites commonly known as “poppers” can present a similar danger.
Anyone taking medicines for chest pain, cardiovascular disease or blood pressure should obtain professional advice before using an ED medicine.
Alcohol and erectile dysfunction medicines
Excessive alcohol consumption can itself make achieving or maintaining an erection more difficult. It may also increase problems such as dizziness or low blood pressure when combined with ED medicines.
Drinking heavily in an attempt to improve confidence before sexual activity can therefore work against the intended effect of treatment.
Which medicine is better?
There is no single answer that applies to everyone.
Some people may prefer sildenafil because they want a shorter treatment window and intend to use medication only when required. Others may prefer tadalafil because its longer duration allows greater flexibility around timing.
Other considerations include:
- other medicines being taken
- cardiovascular health
- kidney or liver function
- possible side effects
- frequency of sexual activity
- previous experience with ED treatment
- whether a daily treatment schedule is medically appropriate
A healthcare professional can assess these factors when deciding which treatment and dose are suitable.
What if sildenafil or tadalafil does not work?
A single unsuccessful attempt does not necessarily mean that a PDE5 inhibitor is ineffective.
Possible factors include taking the medicine incorrectly, insufficient time before sexual activity, a heavy meal in the case of sildenafil, excessive alcohol, insufficient sexual stimulation, anxiety or an underlying medical condition.
The dose should not be increased beyond recommended or prescribed limits simply because the expected response did not occur.
If erectile dysfunction continues despite appropriate treatment, medical assessment is advisable.
Erectile dysfunction can be a wider health issue
Persistent ED can sometimes be associated with cardiovascular disease, diabetes, high blood pressure, hormonal disorders, medication side effects, psychological factors or lifestyle issues.
For that reason, treating erectile symptoms should not replace assessment of a possible underlying cause.
Our Erectile Dysfunction Knowledge Base contains additional information about ED treatments, medicine safety and related health considerations.
Explore sildenafil and tadalafil information
Frequently asked questions
Are sildenafil and tadalafil the same medicine?
No. They are different active ingredients, although both belong to the PDE5 inhibitor group and are used to treat erectile dysfunction.
Does tadalafil last longer than sildenafil?
Yes. Tadalafil may remain effective for up to 36 hours, which gives it a considerably longer treatment window.
Can sildenafil be taken after eating?
It can be taken with food, but food can delay its absorption. A large meal may therefore delay the expected effect.
Does food affect tadalafil?
Tadalafil can generally be taken with or without food because its absorption is not significantly influenced by meals.
Can sildenafil and tadalafil be taken together?
They should not be combined unless a qualified healthcare professional has specifically instructed otherwise. Using multiple erectile dysfunction medicines together may increase the risk of side effects and excessive lowering of blood pressure.
Do sildenafil and tadalafil increase sexual desire?
They are not medicines for increasing sexual desire. They support the physical erectile response when sexual stimulation is present.
Further official information
For independent medical information, see the NHS guidance on sildenafil, tadalafil and erectile dysfunction.
Medical disclaimer
This page provides general educational information and should not be used as a substitute for medical diagnosis or individual treatment advice. Speak with a qualified doctor or pharmacist before starting, changing or combining erectile dysfunction medicines.
