I was taking Zantac alongside an asthma medication... Advair. I started feeling constantly fatigued, couldn't sleep, and in general very very off. If you'll check the Advair reactions part of this site, you'll see alot of people report similar side effects to it.
My stomach started acting up again so i decided to take the Zantac 150 again. First 2 days i was constantly fatigued; dizzy, trembling, nauseous. 3rd day I could not sleep for the life of me. I'm writing this in an insomniac haze, but all things considered I'm not going back on the Zantac again. It's possible taking it again brought up the reactions I'd had to the Advair... but now I wonder which drug it was that I reacted to.