How Does Tadalafil Work?

Understanding how tadalafil works can help you use it more effectively and know what to expect when taking it. This article explains the medication’s mechanism of action in straightforward terms, without excessive medical jargon.

The Simple Explanation

Tadalafil helps blood vessels in the penis relax and widen, making it easier for blood to flow in when you’re sexually aroused. This increased blood flow makes it possible to get and maintain an erection.

The medication doesn’t create sexual desire or cause automatic erections. It simply improves the body’s natural erectile response when sexual stimulation occurs.

The Science: PDE5 Inhibition

To understand how tadalafil works, it helps to know a bit about the normal erectile process.

Normal Erection Process

When you’re sexually stimulated:

Your nervous system releases chemicals in the erectile tissue of the penis
These chemicals cause an enzyme called guanylate cyclase to increase levels of a substance called cyclic GMP (cGMP)
Cyclic GMP causes the smooth muscle in blood vessels to relax
Blood vessels widen (dilate), allowing more blood to flow into the penis
This increased blood flow causes an erection

Where Tadalafil Comes In

An enzyme called phosphodiesterase type 5 (PDE5) breaks down cyclic GMP. When cGMP levels decrease, the erection subsides.

Tadalafil works by blocking or inhibiting the PDE5 enzyme. When PDE5 is inhibited:

Cyclic GMP stays in the system longer
Blood vessels remain relaxed for a longer period
It’s easier to achieve and maintain an erection when sexually stimulated

This is why tadalafil and similar drugs are called “PDE5 inhibitors”.

Why Sexual Stimulation Is Still Required

A common misconception is that taking tadalafil will cause an automatic erection. This isn’t how the medication works.

Tadalafil makes the erectile response easier and more reliable, but it doesn’t initiate the process. You still need:

Sexual thoughts or stimulation
The initial release of chemicals that starts the erectile cascade
Arousal and desire

Without sexual stimulation, tadalafil alone won’t produce an erection. This is actually a safety feature, as it means the medication works with your body’s natural processes rather than overriding them.

Onset: When Does Tadalafil Start Working?

Tadalafil typically begins to work within 30 to 60 minutes of taking it. However, several factors affect how quickly it takes effect:

Individual Variation

Some men notice effects within 30 minutes, while others may not feel the full benefit for up to 2 hours. This variation is normal and can depend on your metabolism and overall health.

Food Effects

Unlike some other ED medications, tadalafil isn’t significantly affected by food. However:

Taking it with a very large meal may slow absorption
High-fat meals can delay the onset of action
For fastest results, taking it on an empty stomach may be beneficial

Alcohol

Small amounts of alcohol are generally acceptable, but excessive drinking can:

Delay the medication’s effects
Reduce the quality of erections
Increase the risk of side effects like dizziness

For more information, see our article on tadalafil and alcohol.

Duration: How Long Does Tadalafil Last?

One of tadalafil’s distinguishing features is its long duration of action.

The 36-Hour Window

Tadalafil can remain effective in your system for up to 36 hours. This is significantly longer than other ED medications:

Sildenafil (Viagra): 4-6 hours
Vardenafil (Levitra): 4-5 hours
Avanafil (Spedra): 4-6 hours

This extended duration is why tadalafil is sometimes called “the weekend pill” – a single dose taken on Friday evening could potentially be effective through Sunday.

What “36 Hours” Means

It’s important to understand that this doesn’t mean you’ll have a constant erection for 36 hours. Rather, during this window:

You’ll be able to achieve erections when sexually stimulated
Multiple erections are possible
You don’t need to time sexual activity as precisely
The medication remains in your system at effective levels

Half-Life

The half-life of a drug is the time it takes for half of it to be cleared from your body. Tadalafil has a half-life of approximately 17.5 hours.

This relatively long half-life explains why:

Effects last much longer than other ED medications
Daily dosing at lower strengths is practical and effective
You need to be aware of interactions for a longer period

For more details on dosing and duration, see our article on tadalafil dosage and how long it lasts.

Different Dosing Approaches

Because of how tadalafil works and its long duration, it can be used in two distinct ways.

On-Demand Dosing

Higher doses (typically 10mg or 20mg) are taken roughly 30-60 minutes before anticipated sexual activity. This approach is suitable for men who:

Have sex less than twice a week
Prefer to take medication only when needed
Want flexibility due to the long duration

Learn more in our guide to tadalafil 10mg and 20mg on-demand treatment.

Daily Dosing

Lower doses (2.5mg or 5mg) are taken at the same time each day, regardless of sexual activity plans. This creates a steady level in your system and may suit men who:

Have sex more than twice a week
Prefer spontaneity without planning around tablet-taking
Also have BPH symptoms that benefit from daily treatment

Read about tadalafil 5mg daily treatment for more information.

Factors That Affect How Well Tadalafil Works

The effectiveness of tadalafil can be influenced by several factors:

Overall Health

Your general health significantly affects how well ED medications work:

Cardiovascular health: Good circulation is essential for erectile function
Diabetes: Can affect blood vessels and nerves involved in erections
Hormonal balance: Low testosterone can reduce the effectiveness of PDE5 inhibitors
Neurological conditions: Can interfere with the signals needed for erection

Other Medications

Some medications can interact with tadalafil or affect erectile function:

Blood pressure medicines: Some types may interact; others may contribute to ED
Antidepressants: Can affect sexual function
Prostate medications: May have synergistic or interaction effects
Other drugs: Always inform your prescriber of all medications you take

This is why a thorough medical assessment is essential before starting tadalafil.

Psychological Factors

Mental and emotional state also plays a role:

Anxiety: Performance anxiety can interfere with the medication’s effectiveness
Stress: Can reduce sexual desire and make erections more difficult
Relationship issues: May need addressing alongside medication
Expectations: Understanding what the medication can and can’t do is important

Lifestyle Factors

Daily habits affect how well tadalafil works:

Smoking: Damages blood vessels and reduces effectiveness
Excessive alcohol: Can interfere with erectile function
Exercise: Regular physical activity improves circulation
Diet: A healthy diet supports overall vascular health
Sleep: Poor sleep can affect sexual function

Why Medical Supervision Matters

Tadalafil affects the cardiovascular system, which is why medical supervision is essential.

Pre-Treatment Assessment

Before prescribing tadalafil, a healthcare professional needs to check:

Your heart health and blood pressure
Other medications that might interact
Conditions that might make tadalafil unsafe
Recent cardiovascular events (heart attack, stroke)
Whether you’re healthy enough for sexual activity

Ongoing Monitoring

Even after starting treatment, periodic reviews are important to:

Ensure the medication is still working effectively
Monitor for side effects or new health issues
Adjust the dose if needed
Review any new medications you’re taking
Check that underlying conditions are being managed

For information about using tadalafil over extended periods, see our article on tadalafil long-term use and safety.

When Tadalafil Might Not Work

Tadalafil is effective for many men, but it doesn’t work for everyone. Potential reasons include:

Inadequate Dose

Sometimes the initial dose isn’t sufficient. Your prescriber might recommend:

Trying a higher dose
Ensuring you’re taking it correctly
Giving it adequate time to work (may need to try it 4-6 times)

Underlying Conditions

Some health issues can prevent tadalafil from working effectively:

Severe vascular disease
Significant nerve damage
Very low testosterone levels
Anatomical problems

These might need to be addressed before ED medication can be effective.

Medication Interference

Other medications you’re taking might reduce tadalafil’s effectiveness or create safety concerns.

Psychological Barriers

Sometimes psychological factors are the primary issue and may benefit from counselling or therapy alongside medication.

Tadalafil’s Effects Beyond Erectile Function

While tadalafil is primarily used for ED, its mechanism of action affects other areas:

BPH Symptoms

By relaxing smooth muscle in the prostate and bladder, tadalafil can help with urinary symptoms related to an enlarged prostate. Some men take it specifically for this reason or benefit from improvement in both ED and BPH symptoms.

See our article on tadalafil for BPH and other conditions.

Blood Pressure Effects

Tadalafil can cause a mild reduction in blood pressure, which is why it must be used carefully with blood pressure medications and is absolutely contraindicated with nitrates.

Read more in our guide on tadalafil and blood pressure.

Frequently Asked Questions

How is tadalafil different from other ED pills?

The main difference is duration. Tadalafil lasts up to 36 hours compared to 4-6 hours for most other ED medications. See our comparison articles for detailed information.

Can I take tadalafil every day?

Yes, if prescribed for daily use. Daily tadalafil involves lower doses (2.5mg or 5mg) taken at the same time each day. This approach requires a prescription specifically for daily dosing.

Does tadalafil increase sex drive?

No. Tadalafil improves erectile function but doesn’t directly affect libido or sexual desire. If low sex drive is an issue, this should be discussed with your healthcare provider as it may indicate low testosterone or other issues.

What if it doesn’t work the first time?

Tadalafil may not work optimally on the first attempt. Healthcare professionals often recommend trying it at least 4-6 times before concluding it’s ineffective. Factors like anxiety, timing, and stimulation level can all affect results.

Can I take more than the prescribed dose?

No. Taking more than prescribed won’t make it work better and will increase the risk of side effects. If your current dose isn’t effective, speak to your prescriber about adjusting it rather than self-adjusting.

Does tadalafil prevent pregnancy or STIs?

No. Tadalafil only addresses erectile function. You still need to use appropriate contraception and protection against sexually transmitted infections.

Summary

Tadalafil works by inhibiting the PDE5 enzyme, which allows blood vessels in the penis to remain relaxed longer, making it easier to achieve and maintain erections when sexually stimulated.

Key points to remember:

Sexual stimulation is still required for tadalafil to produce an erection
It typically begins working within 30-60 minutes
Effects can last up to 36 hours
It can be used on-demand or as a daily medication
Medical supervision is essential for safe and effective use
Many factors influence how well it works, including overall health, other medications, and lifestyle

For more comprehensive information about tadalafil treatment in the UK, see our main guide to tadalafil.