Eh. This is obviously an opinions question, and also slightly dependant on protocols. Our protocols say no nitro without an IV line, and nothing below 90 systolic. If it's 90, yes. If it's 88, then no. Since I'll typically give a nitro before I get an EKG, my first "To give or not to give" is based solely on BP.
In either case, we'll administer fluid to a patient with a BP of <90 systolic, at this point I'll grab my EKG, and per protocols will administer nitro when the pressure reaches or exceeds 90, excepting cases where a diagnostic EKG can reveal acute right sided compromise, or the historian (pt or otherwise) can reveal chronic right sided compromise. Protocols here say no nitrates for people who are preload dependant. Same for morphine.
As far as to what happens when you do give nitro to RVI patients, yes. It's been my experience that if bottoms them out fairly quickly. I'll typically pucker my buttcheeks and squeeze the IV bag as hard as I can. For chonic patients this drop seems to be less dramatic, and I've noticed that most patients who are chronically preload dependant are typically hypertensive to begin with.