Adverse effects of PDE5 inhibitors for erectile dysfunction

Adverse effects of PDE5 inhibitors are dose-dependent. Common effects include facial flushing, headache, dyspepsia, nasal congestion and dizziness. Less common events include disturbance in colour vision (with sildenafil and vardenafil) and back pain (with tadalafil).

The most serious adverse effect of PDE5 inhibitors results from their interaction with nitrates. This produces a profound hypotensive response that may be fatal. Therefore, PDE5 inhibitors must not be used in people taking nitrates or who use the recreational vasodilator drug, amyl nitrite.

Note: Phosphodiesterase type 5 inhibitors are absolutely contraindicated in people taking nitrates due to a risk of fatal hypotension.

Short-acting and long-acting nitrates should not be taken for at least 24 hours after taking sildenafil or vardenafil, or 5 days after taking tadalafil or avanafil; avanafil has a wide range of reported half-lives but they extend to 17 hours and it should therefore be managed similarly to tadalafil. Clearance of PDE5 inhibitors may be delayed in those who:

For males taking antihypertensive therapy (particularly alpha blockers), advise on how to minimise postural hypotension, and check postural blood pressure changes when prescribing a PDE5 inhibitor.