The only
drug interactions on his list of medications is that Prevacid may reduce effectiveness of Plavix. Vertigo is a known adverse reaction for Carvedilol. Dizziness is a fairly common adverse reaction listed for many medications including Furosemide, Diovan, Pravastatin, and Carvediolol. So it seems he is experiencing known side effects for these drugs, but not because they are interacting with each other.