Hi Tom,

Between 2012 and 2014 I got knocked down twice by vestibular dysfunction caused by a viral infection. Both times it came on ridiculously fast. I knew it wasn't a stroke (several years as a medic and pretty okay at it) but I was alarmed nonetheless. Anyway, the first time an ER doc (wife (former nurse) insisted on ER) put me on a prescription antihistamine (plus IV for fluids) that worked quite well.

The second time I was out of town with my wife when it suddenly hit. I was able to get a generic 50mg benadryl and an over the counter nausea suppressant on board before I got too wiped out by the spinning. With those two drugs in my system I managed to tough it out to morning until I could hit up a local doc in the box for a prescription of the aforementioned antihistamine.
Sadly, I can't remember the name of the particular med right now but I can check and post the info later Mon. morning, if you like. It may be of some help to you. It definitely helped me.

All in all everything had calmed down within a couple weeks and I was back on my bike within three weeks at the latest.

Hope it helps. It's an unpleasant state to be in.