At a glance
- PDE-5 inhibitors are active ingredients that are primarily used to treat erectile dysfunction.
- These drugs include sildenafil (e.g. Viagra), tadalafil (e.g. Cialis), vardenafil (e.g. Levitra), and avanafil (e.g. Spedra).
- PDE-5 inhibitors require a prescription in the USA.
What are PDE-5 inhibitors?
Phosphodiesterase-5 inhibitors, PDE-5 inhibitors for short, refer to drugs that are used in particular to treat erectile dysfunction. In addition, they have a blood pressure-lowering effect and are therefore used for high blood pressure in the lungs.
The best-known representative of this group of active ingredients is Sildenafil, which came onto the German market in 1998 under the brand name Viagra.
The effectiveness of PDE-5 inhibitors in erectile dysfunction has been confirmed in numerous studies. The active ingredient tadalafil is also approved for the treatment of benign prostatic hyperplasia (BPH, benign enlargement of the prostate).
How do PDE5 inhibitors work?
The blood vessels of the penis are constricted in the non-erect state, so the erectile tissue contains little blood. During sexual arousal, a messenger substance called cyclic guanine monophosphate (cGMP) is released into the muscle cells. This causes the vascular muscles to relax and more blood to flow into the erectile tissue – the penis becomes stiff.
Erectile dysfunction is usually caused by not enough blood getting to the cavernous bodies of the penis. An erection is then, despite sexual arousal, difficult or even impossible. PDE-5 inhibitors help by relaxing the vascular muscles and thus increasing blood flow.
PDE-5 inhibitors work by blocking the enzyme phosphodiesterase-5 (PDE-5 for short). This is responsible for the breakdown of cGMP and thus influences erectile function. By taking PDE-5 inhibitors, the concentration of the messenger substance increases, and a long-lasting erection occurs.
Since cGMP is only released when there is sexual stimulation, PDE-5 inhibitors only show an effect when there is sexual arousal. The drugs have no positive effect on the patient’s sexual desire.
PDE 5 inhibitors: differences between the drugs
The various active ingredients can differ in the following points:
- Dosage (mg per tablet)
- Duration until the full effect
- Duration of action (half-life)
Overview of the effects of prescription sexual enhancers
|active ingredient||dosages||duration of action||onset of action||effectiveness|
|Avanafil||50 / 100 / 200 mg||approx. 6 hours||after 15 – 30 minutes||up to 59%|
|sildenafil||20 / 25 / 50 / 75 / 100 mg||approx. 4 hours||after approx. 25 minutes||up to 80%|
|Tadalafil||5 / 10 / 20 mg||24 – 36 hours||after approx. 30 minutes||up to 80%|
|Vardenafil||5 / 10 / 20 mg||approx. 4 hours||after 25 – 60 min.||up to 80%|
PDE-5 inhibitors: what side effects can occur?
Like almost every drug, PDE5 inhibitors can also have side effects.
The most common include :
- Reddening of the skin (the so-called flush symptoms)
- visual disturbances
- Stuffy nose
- back and muscle pain
- permanent erection
A detailed description and frequency of the respective side effects can be found in the information leaflet for the relevant medication.
Who shouldn’t take PDE5 inhibitors?
Patients who are already taking other medications to treat high blood pressure or heart disease should consult a doctor before taking a PDE-5 inhibitor.
A combination of nitrate-containing medicines in particular can cause life-threatening circulatory crises.
Patients suffering from serious cardiovascular diseases such as heart failure, stroke, or cardiac arrhythmia should be particularly careful. Due to the increased physical exertion during sexual intercourse, there is a significant health risk.
The drugs are not approved for the treatment of women or minors.
Can you buy PDE5 inhibitors without a prescription?
PDE-5 inhibitors such as Viagra, Cialis, Levitra, Spedra or corresponding generics can legally only be purchased with a prescription.
Buying over-the-counter preparations on the Internet is strongly discouraged. These are often counterfeit medicines that can cause significant damage to health.