Sikkerheden af sildenafil er ikke undersøgt hos følgende patientundergrupper, og dets anvendelse er derfor kontraindiceret: svært nedsat leverfunktion, nyligt overstået slagtilfælde eller myokardieinfarkt, svær hypotension (blodtryk < 90/ 50 mmHg) ved initiering.
The safety of sildenafil has not been studied in the following sub-groups of patients and its use is therefore contraindicated: severe hepatic impairment, recent history of stroke or myocardial infarction, severe hypotension (blood pressure < 90/ 50 mmHg) at initiation.