Phosphodiesterase 5
Also known as: PDE5
Enzyme that degrades cyclic GMP in corpus cavernosum smooth muscle and pulmonary vessels. It is the target of sildenafil, tadalafil and vardenafil.
Combining PDE5 inhibitors with nitrates (nitroglycerin, isosorbide) causes severe, potentially fatal hypotension, by potentiating nitric oxide; they also potentiate hypotension with alpha-blockers and riociguat.
Substrates: cyclic GMP.
Inhibitors: sildenafil, tadalafil, vardenafil.
Inducers: not applicable.
Absolute contraindication: PDE5 inhibitors + nitrates (any form); also avoid with riociguat. Sildenafil and vardenafil are metabolised by CYP3A4 (interaction with ketoconazole, ritonavir, clarithromycin).
DailyMed/FDA (NIH/NLM) — approved labels (sildenafil, tadalafil); EMC-UK (MHRA) — SmPC
