meclizine, sold OTC--as Ren pointed out--as Bonine, also Dramamine Less Drowsy Formula). Most people don't seem to get much help from it, though. (This is my nonscientific conclusion from years of reading a dizziness list.) Antivert did nothing for me.
(But don't minimize the dangers of sneezing... that's exactly how I lost the hearing in my left ear and got a big increase in my dizziness at the same time!! I'm not kidding!!)
If meclizine doesn't work for you, maybe Valium would?