Ondansetron
"I started taking this for "morning sickness" during my 3rd pregnancy.  In the past I had dealt with extreme nausea and vomiting the first trimester which made me so dehydrated I was hospitalized several times.  This time around I was at my wits end and tried all the anti-nausea medicines except this.  After taking it, the nausea completely disappeared.  Like another user I felt dizziness and headache at first but that soon was gone and I was normal.  Can't say enough about this!  A lifesaver for anyone who knows what it's like to throw up for weeks on end."