If you use Metronidazole you will want to avoid PG juices in any concentrate while using it and for several days after stopping use. I had to start on this medication and was vaping an 80/20 blend and it affected me very negatively. Found this on the matter and it lines up with what was experienced. https://www.drugs.com/metronidazole.html Maybe this will spare someone the discomfort if they know to look for it. My skin was on fire.