Related Experiment Video
Updated: Jun 19, 2026

Measurement of Cyclic Guanosine Monophosphate (cGMP) in Solid Tissues using Competitive Enzyme-Linked Immunosorbent Assay (ELISA)
Published on: July 3, 2025
PDE5 inhibitors: in vitro and in vivo pharmacological profile
D Kouvelas1, A Goulas, G Papazisis
1Department of Pharmacology, School of Medicine, Aristotle University of Thessaloniki, Greece. kouvelas@auth.gr
Abstract:
PDE5 inhibitors have been clearly established as first-line therapy for the treatment of erectile dysfunction (ED). Three PDE5 inhibitors--sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis)--are currently approved by the FDA and the EMEA for use in ED, whereas sildenafil is also marketed under a different proprietary name (Revatio) for the treatment of pulmonary arterial hypertension (PAH). A forth PDE5 inhibitor, udenafil (Zydena), is currently marketed. In the present review the molecular basis and the mechanism of action of PDE5 inhibitors is discussed. In addition experimental and clinical data concerning their effects on different tissues, organs and systems is systematically reviewed and their possible beneficial action in numerous disorders is presented.
Related Concept Videos
Treatment for Pulmonary Arterial Hypertension: Phosphodiesterase Inhibitors
Among the PDE5 inhibitors, sildenafil (Revatio) stands out as a competitive and selective inhibitor. It operates by elevating cellular levels of cGMP and augmenting signaling through the cGMP-PKG pathway, promoting vasodilation. Upon oral...
Equivalence: In Vitro and In Vivo Bioequivalence
Drug Product Performance: In Vitro–In Vivo Correlation
Pharmacodynamic Models: Overview
Pharmacodynamic Models: Direct Effect Model and Indirect Response Model
Pharmacodynamics: Overview and Principles
Most drugs' effects result from their interactions with drug receptors or targets within the body. These interactions trigger specific responses at the cellular or systemic level. Drug receptors can be found on the surfaces of cells or within...

