Not for the faint of heart! I love my caffeine, and these are most assuredly loaded with it. Go easy on them. If you're used to a 200mg vivarin, I suggest microdosing these. 1/4 to at most 1/2 at a time. They work fast and hard. You're not going to take these for flavor. They sent me a freebie mint and it was more palatable. If you're looking for a super quick jolt, go for it. It does hit your system harder and faster than any other caffeine I've ingested.