Definition of Intoxication
Penal Code - Chapter 49
(2) "Intoxicated" means:
(A) not having the normal use of mental or
physical faculties by reason of the introduction of alcohol, a
controlled substance, a drug, a dangerous drug, a combination of
two or more of those substances, or any other substance into the
body; or
(B) having an alcohol concentration of 0.08 or
more.
(2) "Intoxicated" means:
(A) not having the normal use of mental or
physical faculties by reason of the introduction of alcohol, a
controlled substance, a drug, a dangerous drug, a combination of
two or more of those substances, or any other substance into the
body; or
(B) having an alcohol concentration of 0.08 or
more.
...and most people incorrectly assume that if their BAC is less than .08, they can't be arrested. Not true.
Legislators gave law enforcement pretty large discretion with the phrase, "...not having the normal use of mental or physical faculties by...any other substance into the body..." Thus, pain pills count and maybe even a Starbucks Double Shot, too.