These extracts are fine. I don't know about all extracts available, but i often use a standardized extract. They have the same alkaloid content and often it's even better than just using vine because they are rid of all the tannins for wich you would normally use an egg-white tek wich is complicated.

This all means no purging and stomach discomfort.

You can use these extracts in powder form. There is one way to test the quality of an extract in advance: if you put a bit of it on your tongue, it should leave a numb feeling there, a bit of a local anestheatic feeling. This means that there's enough THH present in it.