Vardenafil PDE6 inhibition

Adverse effects are short-lived, dose-related, and comprise headache, flushing, nasal congestion and dyspepsia. High doses can inhibit PDE6 which is needed for phototransduction in the retina, and some patients report transient colour vision disturbance. (The more recently developed PDE5 inhibitors, cialis and vardenafil, appear less likely to cause visual upset.) Priapism has been reported. 

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