In short: Tadalafil is a so-called PDE-5 inhibitor and one of the most extensively studied active ingredients for erectile dysfunction. Its hallmark is its long duration of action of up to 36 hours – and the option of taking it daily at a low dose. In this article, you will learn how tadalafil works, when it makes sense, and what you should know about side effects and interactions.
Erectile dysfunction is not a niche topic. It affects a large proportion of men during their lives – and becomes more common with age. Nevertheless, many people do not talk about it, even though there are now highly effective and safe treatments. One of the main active ingredients is tadalafil.
Important to note beforehand: This article is not a substitute for a medical consultation. Tadalafil is prescription-only, and whether it is suitable for you depends on your health, pre-existing conditions, and other medications.
What is tadalafil?
Tadalafil belongs to the group of phosphodiesterase-5 inhibitors (PDE-5 inhibitors for short). Sildenafil (known as Viagra) and vardenafil also belong to the same class of active ingredients. Tadalafil became well-known under the brand name Cialis; today there are numerous generics.
The active ingredient is primarily used for:
- Erectile dysfunction – i.e., erectile dysfunction of various causes
- Urinary symptoms due to benign prostatic hyperplasia (benign prostatic hyperplasia, BPH)
- Pulmonary arterial hypertension, a form of pulmonary hypertension (one of its brand names)
How does tadalafil work in the body?
An erection is essentially a blood flow process. During sexual arousal, the messenger substance nitric oxide (NO) is released in the penile tissue. Through several intermediate steps, this causes the smooth muscle in the corpora cavernosa to relax, allowing more blood to flow in.
An enzyme called phosphodiesterase-5 normally breaks down this reaction. This is exactly where tadalafil comes in: It inhibits PDE-5, so that the vasodilating effect lasts longer and an erection can be achieved and maintained more easily.
The crucial point is: Tadalafil only works during sexual arousal. It is not an “aphrodisiac” and replaces neither arousal nor libido. If there is no sexual stimulus, nothing happens.
The same mechanism also explains its effect on prostate symptoms: PDE-5 is also present in the muscles of the bladder, prostate, and supplying blood vessels. When the enzyme is inhibited, this tissue relaxes, which can relieve urinary symptoms (Yokoyama et al., 2015; Calogero et al., 2018).
The major difference: duration of action
Tadalafil differs from other PDE-5 inhibitors primarily due to its long half-life. While sildenafil usually works for 4 to 6 hours, tadalafil can be effective for up to 36 hours. This is why it is colloquially known as the “weekend pill.”
This results in two practical dosing options:
As-needed dosing
A higher dose is taken before planned sexual activity. Due to the long duration of action, there is no pressure to precisely time the “right moment” – sex can be enjoyed more spontaneously.
Daily dosing (low dose)
A small dose is taken once daily. This maintains a continuous therapeutic level, and an erection is possible at any time when aroused. This option is often chosen when prostate symptoms are also present, as it addresses both problems simultaneously (Yokoyama et al., 2015).
A major review comparing tadalafil and sildenafil directly concluded that both active ingredients are similarly effective – but that many men prefer tadalafil due to its flexibility and reduced dependence on timing (Gong et al., 2017).
How safe is tadalafil?
Tadalafil is considered well-studied and safe when used correctly. Like any medication, it can have side effects. The most common are:
- Headache
- Facial flushing
- Stuffy nose
- Digestive issues
- Back or muscle pain (more typical of tadalafil than other PDE-5 inhibitors)
These side effects are usually mild and temporary. More serious reactions are rare.
When tadalafil must not be taken
Especially important: Tadalafil must never be taken together with nitrates (for example for angina pectoris) or certain blood pressure medications from the alpha-blocker group without medical supervision. Both can dangerously lower blood pressure. Caution is also advised with certain cardiovascular diseases. Therefore, a medical consultation is required before starting any treatment.
Take erectile dysfunction as a warning sign seriously
One point that is often overlooked: Erectile dysfunction can be an early warning sign of vascular problems. Because the blood vessels in the penis are relatively small, atherosclerosis, high blood pressure, or metabolic disorders often become noticeable there earlier than in the heart.
Tadalafil therefore treats the symptom – not always the cause. It is just as important to rule out any underlying conditions. Sometimes there is also a testosterone deficiency behind it, which affects sexual function. You can read more about this in our article Potency, Libido, Testosterone and in Erectile Dysfunction: All in Your Head or a Health Warning Sign?
For further listening: In our podcast Men’s Health, PD Dr. Marco Randazzo discusses in the episode Erectile Dysfunction, Libido & Testosterone how closely these topics are interrelated.
Conclusion
Tadalafil is a proven, well-tolerated active ingredient for erectile dysfunction – with the special advantage of a long duration of action and the option of daily dosing. If prostate symptoms are also present, it can be doubly useful. However, because it is prescription-only and serious interactions exist, its use should be managed by a doctor. And: Erectile dysfunction is always also an occasion to have your vascular and hormonal health thoroughly checked.
FAQ
How quickly does tadalafil work?
With as-needed dosing, the effect usually kicks in after about 30 to 60 minutes and can last up to 36 hours. With daily low-dose dosing, a continuous therapeutic level is maintained.
Does tadalafil cause addiction?
No. Tadalafil does not cause physical addiction. However, some men develop psychological insecurity (“will it work without it?”) – an open conversation with a doctor can help.
Does tadalafil work without arousal?
No. The active ingredient only supports the natural erectile response during sexual stimulation. Without arousal, no erection occurs.
Is tadalafil the same as Viagra?
No. Viagra is the brand name for the active ingredient sildenafil. Tadalafil (known as Cialis) belongs to the same class of active ingredients but works significantly longer.