Examples of these drugs are: nicotine patches; some antacids. In many of the studies, of both fixed dose and titration designs, daily diaries were kept by patients. The following nonprescription or herbal products may interact with sildenafil: cimetidine Tagamet HB , St. Rarely reported side effects include: an erection that will not go away priapism. This leads to more blood flow to the penis, leading to stronger erections.Simon, this question is often asked on have a look there and there are recommended places both in Amsterdam and by /post to uk (which is the cheaper . Tax Refund Partner. The pharmacy of Airport Medical Services at Schiphol is open 24 hours a day, for your last-minute medication. Rarely reported side effects include: an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, priapism can permanently damage your penis. sudden vision loss .