Sildenafil is an inhibitor of the cyclic GMP phosphodiesterase, originally developed as an antihypertensive agent, but now used for the treatment of erectile dysfunction.
Short term effects
Headache, flushing, nausea, vomiting and nasal congestion have all been reported.
Visual disturbance including abnormalities of colour vision and even blindness may occur due to optic neuropathy or retinal artery occlusion.
Cardiovascular features include palpitations, tachycardia and hyper- or hypotension.