Nasal congestion inhibitors

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. 

Most adverse effects of the phosphodiesterase inhibitors are nfild or moderate and self-limited, rarely reqniring treatment discontinuation. In usual doses the most common adverse effects are headache, facial flushing, dyspepsia, nasal congestion, and dizziness, all of which result from inhibition of phosphodiesterase isoenzyme type 5 in extragenital tissues. ... 

Respiratory Vasodilatation induced by PDE-5 inhibitors is responsible for common undesired effects, such as headache, flushing, and nasal congestion. The effect of sildenafil on nasal airways has been measured in 11 young normally potent volunteers using a double-blind crossover design Endonasal volume measured with a nasal telescope fell significantly after a dose of sildenafil, as has previously been shown with another technique in a few patients. 

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