You'll be fine! Take a 1/2 pill and see how you feel. Mine says to take one tablet (I take 37.5 also) daily one hour before breakfast.
I'm smaller, but have found that I am one of the oddballs that deals with one of the rare side effects of drowsiness. I don't get it bad, but i do get it. weird.

35yrs.
5 feet tall.
1stSW-173(highest pregnancy)(lost 40lbs. 4 years ago-putting me at 120lbs.)
SW-138(12.16.06)
CW-134(12.20.06) -4 lbs.
CW-126 (4.26.07) -12 lbs. total
Goal #2-20 lbs. by 5/25/07
GW-110