Tadalafil and Sildenafil may appear similar and that's because they are in many ways. However, there are also a few differences that you should be aware of.
This article will help you delve deeper into the differences and similarities of these two drugs. We will look at how long they take to work, how long they last, and their different strengths and how to take them.
Tadalafil vs. Sildenafil
Sildenafil was released to the market in 1998 and has become one of the most-prescribed medicines in human history. Millions of people have taken it, including those looking to treat erectile dysfunction (ED) (1).
Tadalafil came along in 2003. Eli Lilly, a major drug company, marketed it under the name Cialis, and it later became a generic medication, lowering the cost.
Tadalafil and Sildenafil are both types of medication used to treat problems with achieving an erection, or erectile dysfunction (ED). Both are active ingredients known as phosphodiesterase type 5 (PDE5) inhibitors and both work in a broadly similar way; by improving blood flow to the penis to help achieve an erection and helping to maintain the erection by keeping the blood there.
Tadalafil is available in its generic form, or in its branded form, Cialis. The generic form acts in the same way as Cialis, but usually costs a lot less. Likewise, Viagra is the branded form of Tadalafil.
The choice of Buying Tadalafil or Sildenafil tablets depends on the individual. As well as considering other medical implications, factors such as how often it is required, how long a patient wants the effects to last, and cost, are also considered.
Doctors often recommend Sildenafil and Tadalafil interchangeably. But their differences mean that you may prefer one to the other.
Comparing Tadalafil and Sildenafil
As both medications are in the same category, they have some similarities. Neither causes spontaneous erections; both require sexual stimulation to achieve and sustain an erection. However, there are some differences.
Here are some of the key differences between the two drugs:
Time they take to start working
Sildenafil and Tadalafil take a similar amount of time to work.
For most people, Sildenafil begins to act within 30 to 60 minutes, with peak effects reached at around one hour. (Taking the medicine with or after a high-fat meal can mean it takes longer to act, but it will still have an effect).
Tadalafil works similarly, within 30 to 60 minutes, but can take up to two hours to reach a peak. Food doesn't affect its absorption as much, so it can be more predictable.
Practically speaking, time-to-onset differences are minimal when considering Sildenafil vs Tadalafil. Taking either will work in a similar way.
How long they last
The primary difference between Sildenafil and Tadalafil is how long their effects last. This is why Eli Lilly developed the drug in the first place.
Sildenafil's effects last from 4 to 6 hours, so sexual activity can occur during that window. After that, the drug will wear off and may not produce noticeable effects.
Tadalafil is different. Its effects can last up to 36 hours (a day and a half), which is why some individuals call it "the weekend pill." Taken Friday night, the effects can last until Sunday morning.
You can take Tadalafil daily as a 5mg tablet which allows for continuous effects (i.e. spontaneous sex at any time of day or night). The drug takes around a week to build up in the body, at which point it permanently improves penile blood flow.
Dosing Schedules
The dosing schedules for Sildenafil and Tadalafil are slightly different, given their side-effect profiles and how they work once they enter the body.
Sildenafil dosing
You should take Sildenafil when you anticipate sexual activity.
Most people take between 50 and 100mg around 30 to 60 minutes before sex. If you have never used Sildenafil before, you must start with 50mg.
You should only take one tablet daily, even if you feel its effects wearing off.
It is recommended that Sildenafil is taken up to four hours before its results are needed.
Tadalafil dosing
Tadalafil can be taken "as needed" or daily.
If you take it as needed, a typical dose is 10 to 20 mg taken 30 to 60 minutes before sexual activity (similar to Sildenafil). Again, you should only take this a maximum once per day(2).
If you take Tadalafil daily, you will take 5 mg at the same time every day. After around a week, levels of the medication will build up in the body sufficiently to allow erections at any time. As such, you won't need to plan the medication timing.
What are the dosages of Tadalafil and Sildenafil?
Sildenafil is available in dosages ranging from 25mg to 100mg. A 50mg dosage is usually advised, taken as required, with no more than one tablet taken per day.
Tadalafil comes in strengths of 2.5mg, 5mg, 10mg and 20 mg. The usual dosage is 10mg taken as needed; for regular use, a smaller, daily dose may be recommended by your healthcare professional.
Is 20mg Cialis equal to 100mg Viagra?
In terms of largest available dosage for ED, 20mg of Cialis (Tadalafil) is equal to 100mg Viagra (Sildenafil). Your prescriber will recommend a dosage based on previous experience (if any) of taking the drug and other health indications. Usually, a lower dosage will be recommended (50mg Sildenafil or 10mg Tadalafil for occasional use); your prescriber may then recommend that this dosage is reduced or increased as required.
What happens when you take Tadalafil and Sildenafil together?
You should not take Tadalafil and Sildenafil together. Combining the drugs (which work in similar ways to increase blood flow to the penis) leads to increased risks.
For example, there is a higher likelihood of side effects like low blood pressure. Sildenafil and Tadalafil can cause lightheadedness and dizziness, sometimes leading to fainting(2,3).
Long and painful erections lasting more than four hours could be a problem. These require emergency medical attention to prevent permanent damage to the penis.
Other common side effects, such as flushing, nasal congestion, and headaches, could also become more likely. These symptoms are typical among people taking PDE5 inhibitors but could become worse if they are taken together.
There is no clear evidence that taking these medications together offers any benefits. As such, most medical practitioners believe combining them brings risks that outweigh the benefits. These drugs may have unknown interactions with each other or other medicines you are taking and could lead to potentially dangerous drops in blood pressure.
If you are considering taking Tadalafil or Sildenafil, speak to us. If you are having trouble with one treatment, we may recommend trying the other.
It's normal for a medicine to not work the way you want sometimes. If this happens, we can give you our free, expert guidance.
What happens when you take Tadalafil and Sildenafil together?
You should not take Tadalafil and Sildenafil together. Combining the drugs (which work in similar ways to increase blood flow to the penis) leads to increased risks.
For example, there is a higher likelihood of side effects like low blood pressure. Sildenafil and Tadalafil can cause lightheadedness and dizziness, sometimes leading to fainting(2,3).
Long and painful erections lasting more than four hours could be a problem. These require emergency medical attention to prevent permanent damage to the penis.
Other common side effects, such as flushing, nasal congestion, and headaches, could also become more likely. These symptoms are typical among people taking PDE5 inhibitors but could become worse if they are taken together.
There is no clear evidence that taking these medications together offers any benefits. As such, most medical practitioners believe combining them brings risks that outweigh the benefits. These drugs may have unknown interactions with each other or other medicines you are taking and could lead to potentially dangerous drops in blood pressure.
If you are considering taking Tadalafil or Sildenafil, speak to us. If you are having trouble with one treatment, we may recommend trying the other.
It's normal for a medicine to not work the way you want sometimes. If this happens, we can give you our free, expert guidance.
Tadalafil or Sildenafil: which is better?
Whether you should take Tadalafil or Sildenafil depends on your medical history and current requirements. Mostly, their effectiveness is similar, so they are equally good at helping you maintain erections. However, individual responses may be different. You may find that Sildenafil works better than Tadalafil for you, or vice versa.
The time they take to work is also similar. Sildenafil and Tadalafil start acting on penile tissue within 30 to 60 minutes. However, Tadalafil may work slightly better if you eat food at the same time. As such, it could be a better option if you anticipate sexual activity after a large meal.
Duration is quite different, with Sildenafil lasting 4 to 6 hours and Tadalafil around 36 hours. As such, the latter may be a better choice for some people.
Whether to take Sildenafil or Tadalafil will usually be left to your prescriber's discretion, based on your circumstances, physical health and needs. If you anticipate using ED medication more than twice a week, Tadalafil in a smaller dose may be recommended. Likewise, because Tadalafil tends to last longer, it allows for more sexual spontaneity, so if you anticipate having sex more than once in 36-hour period, it may be the right option for you.
Ultimately, Tadalafil and Sildenafil are not the same. However, there is no universally "better" choice for everyone, which is why both drugs are still on the market. Many people begin with sildenafil and then move to tadalafil if necessary, but not always.
Choosing the right medication depends on a host of factors, which is why at Oxford Online Pharmacy our prescribers will ask you a range of questions so that they can determine the best medication to meet your needs and lifestyle.
Simply choose the medication that you think will be best for you, then complete the online consultation, giving as much accurate information as possible before you add the medication to your basket. Your prescriber will then issue a prescription and approve your purchase or advise you on a more suitable treatment.
References
Connelly D. Three decades of Viagra. The Pharmaceutical Journal. 2017 [cited 2025 Mar].
Tadalafil 10mg film-coated tablets - Summary of Product Characteristics (SmPC) - (emc) [Internet]. [cited 2025 Mar].
Sildenafil 100 mg film-coated tablets - Summary of Product Characteristics (SmPC) - (emc) [Internet]. [cited 2025 Mar].