I figured out how to get it open. Those little beads looked like candy, so I ate them, though they really didn't have any taste, which was disappointing.
I then paused to read the label, and noted the DO NOT EAT. (Pretty sure the package I found as a kid didn't have the confusing quotation marks.) I could read well enough to understand. So I took the package to Mom and explained what I'd just done.
I don't remember what she ended up doing. Just made me drink some extra fluids for the next little bit, I think. And probably laughed at me after I'd gone to bed.