Are you taking any of the following medications? - Any treatment for erectile dysfunction apart from Viagra (sildenafil), Levitra(vardenafil) or Cialis (tadalafil), Spedra(avanafil). - Medicinal nitrates such as glyceryle trinitrate, isosorbide mononitrate or isosorbide dinitrate and Nicorandil (including oral, transdermal and sublingual) - Recreational drugs prohibited by law (Class A, B or C). - Recreational nitrates such as amyl nitrate known as 'poppers' - Alpha blockers (used to treat high blood pressure or urinary symptoms associated with benign prostatic hyperplasia, and including tamsulosin, doxazocin, prazocin terazocin & indoramin). Medicines to treat high blood pressure - Warfarin - used to prevent heart attacks, strokes and blood clots. - Anti-virals including (Atazanavir, etravirine, fosamprenavir, indinavir, nelfinavir, ritonavir, saquinavir) - Anti-fungal medication such as Ketoconazole or itraconazole. -Quinidine/procainamide/amiodarone, Theophylline, Erythromycin/clarithromycin/cimetidine, phenobarbital, phenytoin and carbamazepine, (anticonvulsant medicines).