Hi Triggerdog:

While you are correct in assuming that the medications are similar, what you have to understand is how they are prepared. Both are benzodiazepines, but you need to understand the chemistry of each drug.

Valium (diazepam) is: 7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one and is available in tablets containing 2 mg, 5 mg or 10 mg. 

Ativan (lorezapam) is: 7-chloro-5(2-chlorophenyl)-1,3-dihydro-3-hydroxy-2H-1, 4-benzodiazepin-2-one and is available in tablets containing 0.5 mg, 1 mg, or 2 mg.

While I am not going into a chemistry lesson here, I want you to see that they are not identical drugs and the doses offered by prescription are different.  If they were identical, they would have the identical generic names. They have slightly different ways in which they work, and slightly different ways in which your body adsorbs them.

However, you should really speak with your doctor about these concerns.

Best of luck,

Dr. Diana Walcutt

*Dr. Walcutt is a Psychologist who has taught classes on psychopharmacology at the doctoral level. Her answers are not intended to diagnose or treat any medical or mental disorder. Any information given in a post about medication is for educational purposes only, and primarily to aid you in having an informed discussion with your own Psychiatrist/Physician.