Dear Howard, Elderpyl is notorious for causing insomnia in some people ...I know as I am one of them. Dr. Knoll (pronounced "Ka-nol) the pharmacologist who "invented" selegiline hydrochloride, (the generic chemical name for eldepryl), tells us that the body can only assimulate 10 mg a day of this drug , so it makes little dif when you take it ....but if some of us want to sleep at night, you take the second tab before noon. The story of selegiline is wild. You would think it was fiction if there wasn't proof. The story and the proof is in "Parkinson's Disease: The Mystery, the Search and the Promise". It is publisshed by PIXEL PRESS, P O BOX 3151, TEQUESTA, FLORIDA 33469 for $16.95 return postage pre-paid. The ISBN # is 0-9620354-1-6 I hope this helps understand why most doctors RX the drug for breakfast and noon. VernD