Sildenafil belongs to the group of phosphodiesterase-5 inhibitors. It has a vasodilatory effect and is used to treat erectile dysfunction (erectile dysfunction). Originally developed as a treatment for angina pectoris, the drug is also used to treat pulmonary arterial hypertension. Preparations containing sildenafil are usually administered as tablets and are available only on prescription in Germany, Austria and Switzerland.

Drugs with Sildenafil

Drug Substance(s) Authorisation holder
Vizarsin 100 mg film-coated tablets Sildenafil Krka, D.D., Novo Mesto
Vizarsin 50 mg film-coated tablets Sildenafil Krka, D.D., Novo Mesto
Vizarsin 25 mg film-coated tablets Sildenafil Krka, D.D., Novo Mesto
VIAGRA 100 mg film-coated tablets Sildenafil Pfizer Limited
VIAGRA 50 mg film-coated tablets Sildenafil Pfizer Limited



Sildenafil is an inhibitor of the enzyme phosphodiesterase-5. Phosphodiesterase causes a breakdown of the neurotransmitter cGMP. This substance causes a slackening of the muscles at the erectile tissue of the penis and promotes the inflow of blood. Thus, if PDE-5 is inhibited, the rate of degradation of cGMP decreases (levels of cGMP remain elevated) and the erection can be better maintained.


Sildenafil is rapidly absorbed from the gastrointestinal tract and reaches its maximum blood concentration 30-60 minutes after ingestion. Sildenafil is approximately 96% protein bound and has a half-life of approximately 3-5 hours. Sildenafil is broken down in the cells of the liver by enzymes of the CYP450 family. It is then mostly excreted in the stool.

Drug interactions

It may interact with drugs that are also metabolized by the CYP450 enzyme system. These include ketoconazole, itraconazole, sequinavir, erythromycin, and cimetidine. The potent CYP3A4 inhibitor ritonavir may result in excessive plasma levels of sildenafil. When taken concomitantly, life-threatening side effects are the possible consequence.


Side effects

Possible side effects are flushing, dizziness, headache, dyspepsia, nasal congestion and visual disturbances. In case of overdose, similar side effects may occur, but they are usually more severe.

There is no evidence that sildenafil is carcinogenic or genotoxic. Sildenafil should be administered to pregnant women and nursing mothers (for the treatment of pulmonary arterial hypertension) only in extreme emergencies.

Chemical & physical properties

ATC Code C02KX06, G04BE03
Formula C22H30N6O4S
Molar Mass (g·mol−1) 474,58
Physical State solid
Melting Point (°C) 187–189
PKS Value 5.99
CAS Number 139755-83-2
PUB Number DB00203
Drugbank ID DB00203

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All information used for the content comes from verified sources (recognised institutions, experts, studies by renowned universities). We attach great importance to the qualification of the authors and the scientific background of the information. Thus, we ensure that our research is based on scientific findings.
Markus Falkenstätter, BSc

Markus Falkenstätter, BSc

Markus Falkenstätter is a writer on pharmaceutical topics in Medikamio's medical editorial team. He is in the last semester of his pharmacy studies at the University of Vienna and loves scientific work in the field of natural sciences.

Mag. pharm. Stefanie Lehenauer

Mag. pharm. Stefanie Lehenauer

Stefanie Lehenauer has been a freelance writer for Medikamio since 2020 and studied pharmacy at the University of Vienna. She works as a pharmacist in Vienna and her passion is herbal medicines and their effects.

The content of this page is an automated and high-quality translation from DeepL. You can find the original content in German here.


Drugs that contain Sildenafil

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