I can assure you that pain meds are still QUITE available in farmacias in mexico.

Plotinus nailed that one 100%...the 'official' fed stance in mexico is "no meds w/out a script", but the reality is, the farmacia will take your cash most of the time w/ no script.
It's just not really enforced. And if 1-2 farmacias will supply meds w/ no script, the rest certainly wont sit by and lose busines if they dont have to.

It's funny....every couple of years you hear "the mexican govt is cracking down and wont sell pain meds or scheduled meds w/out a script anymore...really...they mean it this time..." Hahaha. I think it's more likely a mild scam by the farmacias to jack up pricing once in a while when they get their customers in a panic about it. (kidding)

As long as people are willing to pay, I am pretty sure the farmacia owners will always find a way to keep the biz going...

-satchmo