So, this is a fascinating development in pain research. This is, in my estimation, the textbook definition of a double-edged sword.
To nutshell: Neuroscientists at Georgia State University have discovered the mechanism by which female brains literally do not respond to morphine the same way as male brains. Miroglial cells (the brain's immune response) view morphine as a pathogen in the brain and so work hard to clean it up (therefore rendering the morphine less effective for analgesia); and these cells are more active in female brains than male brains. Suppressing these cells makes morphine work better - which is why it doesn't work for females as well as males.
Here's the pointy bits of that sword, as I see them: There is no discussion (that I know of - but please tell me if I'm wrong!) as to what the effects are (short term or long term) of suppressing one of the brain's immune responses. Does this have an effect on the body's immune response? Does it mean the brain is left more vulnerable to actual pathogens? This is promising and powerful but these questions need to be answered.
On the other hand, here's the good bits: There is now a known mechanism by which female brains process morphine differently. Women who need more pain relief compared to men of similar body weight are not "weak" or "whining" or "hysterical". Females literally clear that shit out of the synaptic gaps faster, thank you very much.
So be a good doctor and give the lady her morphine.
http://neurosciencenews.com/pain-sex-differences-6189