Sildenafil and tadalafil

Sildenafil and Tadalafil: What Are They?

Sildenafil and Tadalafil are medications used to treat erectile dysfunction (ED) in men. Sildenafil is also known by its brand name, Viagra, while Tadalafil is commonly referred to as Cialis. Both medications belong to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. They work by increasing blood flow to the penis, allowing a man to achieve and maintain an erection.

How Do Sildenafil and Tadalafil Work?


Sildenafil works by inhibiting the action of an enzyme called phosphodiesterase type 5 (PDE5). This enzyme is responsible for breaking down a chemical called cyclic guanosine monophosphate (cGMP), which is produced when a man is sexually stimulated. cGMP is responsible for relaxing the blood vessels in the penis, allowing blood to flow in and causing an erection.

By inhibiting PDE5, sildenafil increases the levels of cGMP in the body, leading to increased blood flow to the penis and an erection.


Tadalafil works in a similar way to sildenafil, by inhibiting PDE5 and increasing levels of cGMP. However, tadalafil has a longer duration of action than sildenafil, meaning it can be effective for up to 36 hours compared to sildenafils 4-5 hour duration.

How Are Sildenafil and Tadalafil Used?

Both sildenafil and tadalafil are available as oral tablets, which are taken before sexual activity. Sildenafil is typically taken 30-60 minutes before sex, while tadalafil can be taken up to 36 hours before sex.


Sildenafil is available in three strengths: 25mg, 50mg, and 100mg. The recommended starting dose is usually 50mg, but this may be adjusted based on individual response and tolerability.


Tadalafil is available in two strengths: 10mg and 20mg. The recommended starting dose is usually 10mg, but this may be increased to 20mg based on individual response and tolerability.

Are There Any Side Effects?

Like all medications, sildenafil and tadalafil can cause side effects. Common side effects include:

- Headache

- Flushing

- Nasal congestion

- Dizziness

- Upset stomach

In rare cases, both medications can cause more serious side effects such as:

- Sudden vision loss

- Hearing loss

- Chest pain

- Fainting

- Priapism (a prolonged erection lasting more than four hours)

If you experience any of these side effects, seek medical attention immediately.

What Are the Differences Between Sildenafil and Tadalafil?

While sildenafil and tadalafil are both PDE5 inhibitors used to treat ED, there are some differences between the two medications.

Duration of Action

The most significant difference between sildenafil and tadalafil is their duration of action. Sildenafil has a duration of action of around 4-5 hours, while tadalafil can last up to 36 hours.

Onset of Action

Sildenafil typically takes around 30-60 minutes to take effect, while tadalafil can take up to 2 hours to work.

Food Interactions

Sildenafil may be affected by food intake, particularly high-fat meals, which can reduce its effectiveness. Tadalafil is less affected by food intake and can be taken with or without food.

Which Medication Should I Choose?

The choice between sildenafil and tadalafil will depend on individual needs and preferences. If you require a medication with a longer duration of action or are looking for greater flexibility with timing of sexual activity, tadalafil may be the better option. If you prefer a medication with a quicker onset of action or have concerns about food interactions, sildenafil may be more suitable.

It is important to speak with your healthcare provider before starting either medication to determine the most appropriate treatment plan for your individual needs.

The Bottom Line

Sildenafil and tadalafil are both effective treatments for ED. While they work in similar ways, there are some differences between the two medications. It is important to speak with your healthcare provider about the most appropriate treatment option for your individual needs.

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