One medicine that is known to increase sleepiness is called Clonidine. It is a patch that is sometimes used to reduce high blood pressure. I took it for 3-4 months and sleepiness was really bad. Doctor finally switched me to Metoprolol which has been effective in reducing my b.p. and not making me as sleepy. Also, I recently learned that I have a paralyzed diaphragm on one side which may reduce my blood oxygen levels, especially at night. Sleep study at Mayo (Rochester) is not until mid May.