I will refer to Gutmacher's book, Florida Firearms, Chapter Seven, p.119...
"If you're already under the influence of alcohol or any other harmful or illegal chemical substance, to the extent your normal faculties are impaired, it is unlawful to have a loaded firearm in hand, or to fire it. If you do, it's a second degree misdemeanor, unless you're acting in lawful self defense, or defense of your property.
It will also cause the loss of your Concealed Weapons Permit, if you have one."
Reading on...
"If a law enforcement officer has probable cause to believe you were using the firearm while under the influence, he can require you to take a breath test for alcohol, and a urine test for drugs. If you caused death or serious injury to anyone, he may take blood, and take it by force if you refuse."
Gutmacher then goes on to summarize...
"Personally, I don't think you should be walking around with a loaded firearm if you are anything other than stone cold sober unless somebody or something is coming at you, otherwise it is too damn risky. On the other hand, the statute is more than fair, and does not penalize carry, only the actual use, or in hand possession."
IMHO, in the end, anytime you use a weapon you will be under exacting legal scrutiny, so carrying a weapon while under the influence of pain medication is not an ideal situation. While not illegal to carry, if you are forced to use the weapon, you had best be 100% correct and lawful, as knowing you are taking medications that will impair your judgment, abilities and thinking can and will be an issue if not only in the criminal court, but any subsequent civil action that likely will be brought against you.
That said, if you are alive and if not for the use of your weapon you would be dead, then the choice is clear.