Any reason you can think of to avoid the combination of cannabis and one of these drugs sildenafil, vardenafil, or tadalafil? For that matter, any reason you can think of to avoid any or all of the above?
There are no significative interactions described between use of cannabis and PDE-5 inhibitors as sildenafil, tadalafil or vardenafil. Both substances reduce blood pressure and, theoretically use of cannabis under these drugs could enhance this risk. But there are no scientific reports or published cases of this problem so the risk seems unlikely. Poppers are, in fact, the only drug dangerous in combination with these prescription drugs.