Expert: Barbara Judge - 7/24/2007

Question
What is the difference in the  Diphenhydramine Hcl and Diphenhydramine Citrate? I know the "D"Hcl is the generic for Benadryl and I understand its usage. Advil PM has "D" Citrate. If I take "D"Hcl and Ibuprofen separately (same dosage as in Advil PM) I do not experience the same level of drowsiness or the residual morning sleepiness that I get if I take just the Advil PM alone. The Hcl wears off after about 4 hours and I'm alert. The citrate still has me groggy after 8 or 9 hours. Can you briefly summarize why there is such a difference, when all the sources I've checked say the two "D"s are the same?

Answer
    There really is no logical reason as to why you react so differently to the 2 different salt forms of diphenhydramine.  The difference between the two is in the inactive portion of the molecule which the body must split off in order to solubilize the active drug.  It is possible that is is more difficult for your body to metabolize one chemical entity over the other, but this would be extremely rare.  I have never heard of any type of condition which involves symptoms like what you are describing.  Unfortunately, with medicine, just because it hasn't been documented it does not mean it is impossible.  I would recommend that the easiest thing you can do is avoid the use of Advil PM to avoid the prolonged drowsiness.

Thanks

Barb Judge