My old medical director used to say "There is no higher calling than to save another man's life, or to TAKE AWAY HIS PAIN'
I believe this is true. Now, taking into account that a doctor normally does want to assess a patient's pain, I would advise against snowing your patient. You typically aren't going to administer so much medication as to mask the pain entirely.
I for one can't stand to see someone in pain, and approach it from the perspective of "If that was my mother...."
In addition to that...pain meds may be a long time coming after you drop the patient off at the ER, considering Nurse Ratchet has to receive her physician's order, get said narcotic, find a co signer, etc etc... I say take the edge away, and let the patient thank you. As long as you don't snow them and you stick to the protocol, then no one can fault you...
Treat the treatable, take away the pain, and above all else, do no harm.