CYP2D6 poor

"6–10% of the Caucasian population ... are "poor metabolizers"; they have little CYP2D6 and codeine is less effective for analgesia in these patients"

Nor as an antitussive, I would add, even at 2 tsp (twice what I'm supposed to take). I'm not light-headed or drowsy either.

I'll try Pamela's honey suggestion next.