I have been using selegiline in low doses for nearly 9 months now. For around the first 7 months the selegiline always had the same effect on me. Mostly increased drive and mood, as well as enhanced concentration. For that same period of time I had always used a magnesium supplement containing bioperine, as well as 500mg of resveratrol every morning. Since I stopped using both of those I have noticed that the effects of the selegiline have changed. I still feel it, but the effects seem blunted somehow.
Both bioperine and resveratrol are reported to have an effect on liver enzymes. Bioperine more notably but I used it far less consistently than the resveratrol.