Doctors need to be very cautious when dosing patients in different age groups. What may be considered the standard dose for people in their late teens up through the 60 y/o range, but that same dose should never be given to people under 18 years of age or folks in their 70's and beyond.
The sedative affect is different for everyone, so I can't give you a definite answer as to when your body will adjust to the new dose. But while you are feeling this sedative effect, it would be best if you didn't drive or do anything that could put you at risk. Try to think of it as a chance to lay around and read some books, catch up on some movies......NAPS!
Since it won't be that long before you'll be able to see your doctor, I think it's best that you don't second guess him and change the dose. If he decides to drop you back to your original dose, you will not have been on the higher dose long enough to cause any problems.
Peace
Greenlydia