Sildenafil Vs Tadalafil | Accurate Advice From A Clinician
Written By Kobi Nathan, Pharm.D., M.Ed., CDP, BCGP, AGSF
Sleep Disorders
December 6, 2023

Sildenafil vs Tadalafil: Which one should you use?

In my clinical experience, many men prefer tadalafil (Cialis) because it works faster, lasts longer, and can be taken with or without food, unlike sildenafil (Viagra), which must be taken on an empty stomach.

But, it is not for everyone, and some men still prefer sildenafil.

Read on to learn more…

If you have been diagnosed with an enlarged prostate or low testosterone, there is a high likelihood that you’re experiencing erectile dysfunction.

I encourage you to click the links above to read my in-depth articles on those topics.

I highly recommend you read them because they are not generic, vague posts often found on bigger websites.

My clinical experience is woven into these articles, and I believe you will benefit greatly from reading them.

Okay, back to the topic of this article…you may be wondering which medication is right for you: sildenafil or tadalafil.

Both drugs are popular choices for treating ED, and they work by increasing blood flow to the penis.

However, you should be aware of some important differences between the two.

Firstly, sildenafil is the active ingredient in Viagra, while tadalafil is the active ingredient in Cialis.

Both drugs belong to the same phosphodiesterase type 5 (PDE5) inhibitors class.

They work by relaxing the smooth muscles in the walls of the blood vessels in the penis, which allows more blood to flow into the area and helps you achieve and maintain an erection.

However, there are some differences in the onset time and duration of action between sildenafil and tadalafil, which we’ll explore further in this article.

Key Takeaways

  • Tadalafil and sildenafil are both medications used to treat erectile dysfunction by inhibiting phosphodiesterase type 5 (PDE5) and increasing blood flow to the penis.
  • Sildenafil starts to work in 30 to 60 minutes and lasts up to four hours, while tadalafil starts to work within 30 minutes and can be active for up to 36 hours.
  • Both medications can cause side effects such as headaches, nausea, and facial flushing.
  • Sildenafil must be taken on an empty stomach, while tadalafil can be taken with food.
  • Sildenafil is the active ingredient in Viagra, while tadalafil is the active ingredient in Cialis, and both can now be manufactured by other companies as well.

How tadalafil and sildenafil work for erectile dysfunction (ED)

You already know that sildenafil and tadalafil are both used for the treatment of erectile dysfunction (if you want to know all about ED and all of the treatments available for it, you can read my very detailed article here) by inhibiting phosphodiesterase type 5 and increasing blood flow to the penis.

But it’s important to note that this is how they work to help you achieve and maintain an erection during sexual stimulation.

When you become sexually aroused, your body releases nitric oxide, which then stimulates an enzyme called guanylate cyclase.

This enzyme produces cyclic guanosine monophosphate (cGMP), which relaxes the smooth muscle in the penis and allows blood to flow into the corpora cavernosa, creating an erection.

However, the body also produces an enzyme called phosphodiesterase type 5 (PDE5), which breaks down cGMP and causes the penis to return to its flaccid state. Sildenafil and tadalafil inhibit PDE5, allowing the cGMP to remain in the penis for longer periods of time.

This results in improved blood flow and a firmer, longer-lasting erection during sexual stimulation.

Differences between sildenafil and tadalafil

The duration of action for sildenafil and tadalafil differ significantly.

This difference in duration is a significant factor when choosing between the two medications, as it allows for a longer window of opportunity for sexual activity with tadalafil.

Here are three key points to keep in mind when considering the duration of action for sildenafil and tadalafil:

  1. Sildenafil is a short-acting medication; its effects typically last up to four hours after taking it.
  2. On the other hand, tadalafil is a longer-acting medication, and its effects can last for up to 36 hours after taking the medication.
  3. The longer duration of action for tadalafil means that it can provide a more spontaneous and natural sexual experience, as there is a longer window of opportunity for sexual activity.

Dosage of sildenafil and tadalafil


  • 50 mg tablet once daily as needed one hour before sexual activity (may be taken up to 4 hours before).
  • If adverse effects occur, decrease the dose to 25 mg once daily.
  • If you are experiencing incomplete dose-response, you may increase (with the doctor’s approval) the dose to 100 mg daily.


  • 10 mg as a single dose, once daily, at least 30 minutes prior to sexual activity.
  • Do not exceed more than 5 mg every 72 hours if you have reduced kidney function.
  • Do not exceed more than 10 mg if you have reduced liver function.

Adverse effects of sildenafil and tadalafil

One potential concern to remember when taking sildenafil or tadalafil is the possibility of experiencing side effects.

Although these medications are generally safe and well-tolerated, some individuals may experience adverse reactions.

Negative effects of both medications include:

  • Headaches.
  • Nausea.
  • Dizziness.
  • Facial flushing.
  • Blurred vision.
  • Priapism (erection that won’t go away – this must be treated as a medical emergency! – blood gets trapped in the penis, becomes de-oxygenated, and starves penile tissue of oxygen and nutrients, which then starts dying).

Other side effects seen specifically with tadalafil may include:

  • Nasal congestion (stuffy nose).
  • Indigestion.
  • Muscle pain.

These side effects are typically mild and go away on their own within a few hours.

However, if you experience severe or persistent side effects, you should seek medical attention right away.

In rare cases, sildenafil and tadalafil can cause more serious side effects, such as sudden vision loss (Non-arteritic ischemic optic neuropathy), hearing loss, or priapism, as mentioned above.

If you experience any changes in your vision or hearing while taking these medications, you should stop using them immediately and seek medical attention.

Additionally, these medications can interact with certain other drugs, so it’s important to inform your healthcare provider about all medications you are taking before starting treatment with sildenafil or tadalafil.

Overall, while the adverse effects of these medications are usually mild, it’s important to be aware of the potential risks and to seek medical attention if necessary.


The section below contains affiliate links. I may earn a small commission at no additional cost to you if you decide to purchase products using these links. Thank you for supporting my website and helping me post more practical content for you!

My alternative recommendations to sildenafil vs tadalafil

L-citrulline, an over-the-counter dietary supplement, may be an option to consider if you want to avoid prescription ED medications.

There is some clinical evidence to suggest that this supplement can help increase and maintain the rigidity of an erection and contribute to a satisfying sexual encounter.

L-citrulline gets converted to L-arginine in the kidneys, which indirectly increases nitric oxide, ultimately leading to an erection.

There is also evidence to suggest that L-citrulline may make the penile muscles release a substance called vascular endothelial growth factor (VEGF), which in turn may lead to the synthesis of more blood vessels (angiogenesis) in the penis.

If you want this dietary supplement, is an excellent company that produces clean supplements without unnecessary additives.

You can purchase their pure, additive-free L-citrulline product here.

Ingredient label for L-citrulline powder supplement

I use many of their products, including protein and creatine powders.

Relationship between mood and erectile dysfunction

The research is clear – multiple studies confirm a causal relationship between mood and erectile dysfunction.

If you are looking for a non-prescription option to maintain mental clarity and focus, Performance Lab products may help.

I use many of their products because I like their transparency and sound ethical practices.

Every ingredient is research-backed, and its dose is clearly listed on the product label.

And, there is no gimmicky “proprietary blend” nonsense commonly seen in other products.

I highly recommend their MCT Energy Oil and Mind Lab Pro.

Click the links to learn more and purchase directly from the company’s official website.

I highly recommend reading my detailed Mind Lab Pro review if you want to learn more.

Frequently Asked Questions

Are there any restrictions on taking sildenafil vs tadalafil with certain foods or beverages?

There are no restrictions on taking sildenafil or tadalafil with food or beverages, but heavy meals may delay the onset of action.

Alcohol consumption should be limited as it can increase the risk of side effects.

Can sildenafil or tadalafil be used to treat other medical conditions besides erectile dysfunction?

Sildenafil and tadalafil can also be used to treat pulmonary arterial hypertension (PAH), a condition that affects the blood vessels in the lungs.

They work by relaxing the blood vessels and improving blood flow.

How do sildenafil vs tadalafil compare to other treatments for erectile dysfunction, such as penile injections or vacuum pumps?

Penile injections and vacuum pumps are alternative treatments for erectile dysfunction.

They work by increasing blood flow to the penis.

However, they may cause pain, discomfort, or bruising, while sildenafil and tadalafil have fewer side effects and are more convenient to use.

Is there a difference in effectiveness between brand-name and generic sildenafil vs tadalafil?

There is no significant difference in effectiveness between brand-name and generic versions of sildenafil or tadalafil.

Both contain the same active ingredients and are regulated by the FDA to ensure safety and efficacy.

Are there any long-term health risks associated with taking sildenafil or tadalafil for extended periods of time?

Extended use of sildenafil and tadalafil for erectile dysfunction treatment does not pose any significant long-term health risks when taken as prescribed.

However, they may cause side effects like headaches, nausea, and facial flushing.

Consult with your doctor if you experience any adverse effects.

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