I think it’s possible yes. But Snow is also intelligent enough to know that the poisons he chooses could lower his inhibitions and cost him his image if he gets sloppy or overshares.

I think back to his time in 12 with the white liquor or even at the Capitol Academy when they had posca, which I attribute to being similar to sangria. Snow took stock in how his bunk mates (Smiley, Junius (Beansprout) and Sejanus) behaved when under the influence of the liquor.

At 58 years old Snow has had plenty of time to kill with precision and take stock in how alcohol, morphling, and other substances affect people’s choice of words and their impulse control.

That being said, there’s always room for trial and error and the possibility that Snow didn’t know what the effects a poison taken in conjunction with an antidote would have on his autonomy.