Roflumilast
"Originally I had no side effects on Daliresp and noticed better breathing, but after two months I noticed a moderate tremor.  PCP put me on primidone for benign essential tremor.  After another month the tremor increased significantly and I asked my pharmacist what drugs could be causing this.  After she told me Daliresp, I went online to the manufacturer's website and discovered that primidone should NOT be used with Daliresp.  Since it is the weekend and my tremors are continuing to increase to the prevention of some normal activities, I've stopped using both until I can talk to doctor's on Monday. "