Phosphodiesterase type V (PDE5) inhibitors are used in the treatment of erectile dysfunction. They are also used in the management of pulmonary hypertension.

Mechanism of action

PDE5 inhibitors cause vasodilation through an increase in cGMP leading to smooth muscle relaxation in blood vessels supplying the corpus cavernosum.

Adverse effects

  • visual disturbances e.g. blue discolouration, non-arteritic anterior ischaemic neuropathy
  • nasal congestion
  • flushing
  • gastrointestinal side-effects
  • headache


  • patients taking nitrates and related drugs such as nicorandil
  • hypotension
  • recent stroke or myocardial infarction (NICE recommend waiting 6 months)