Nitrates are the one absolute no; other heart drugs need care
In men on isosorbide mononitrate, 50mg of sildenafil dropped standing blood pressure by 52/29 mmHg against 25/15 on placebo. Against amlodipine it added about 8/7.
What the study found
Nitrates are banned outright; other heart drugs only need care
In men on isosorbide mononitrate for angina, 50mg of sildenafil dropped standing blood pressure by 52/29 mmHg, against 25/15 on placebo. Against amlodipine, an ordinary blood-pressure drug working by a different route, it added about 8/7. That is the difference the ban is drawn on.
The caveat · Only 31 men, all with stable angina
Thirty-one men in total across two crossover trials, all with stable angina, so the exact size of the fall need not transfer to anyone else. Blood pressure was what these trials counted, not faints, heart attacks or deaths, and a trial counting those in people on nitrates will never be run.