My brother felt dizzy and had for a time (until he took meds by doctors) had his heart beating in excess of 200 beats per minute.

After a while the doctors decided to take the drip (meds) off of him and he stood up and felt dizzy and his pulse began rising rapidly.

He has been working more hours than usual and is stressed a bit due to a new job.
He has no history of illness.
question - What could this possibly be?

sounds like a heart or low blod presure problem
he needs the doctor to deside what is wrong
that is to fast of a heart rate
it should be about 50 to 99