Rob,

The reference I used that stated phenergan was an antihistamine (primary
mechanism of action):
Gellis and Kagan, Current Pediatric Therapy, volume 15, page 267-(1996)
A respected pediatric pharmacotherapeutic text.  Oops it is also a
phenothiazine (quick check in my Harriet Lane Handbook).  I unfortunately
don't have Hale and my pharm books are from the 80's-very musty .

I think the other risk aspect that separates phenergan from the drugs such as
prochlormeperazine and other dopamine antagonists is that the latter drugs
also lower seizure threshold (another nasty side effect).  I think that's the
other reason why proponents of promethazine (phenergan) prefer it over the
dopamine antagonist classes  of antiemetics.  I'm not a great fan of phenergan
but use it sparingly in kids over 2 (and only for the antiemetic and
antinausea indication never for cough suppression as others do).

Thanks for the check!

Mimi