As you can see, they're scored down the middle, so it's pretty easy to break them in half and get 50 mgs. To break one of those halves in half takes a sharp knife, but it's doable. I know this because I did it yesterday. Then I put the half of a half tablet back into the medicine bottle.
Where, this morning, I mindlessly grabbed it, along with a whole 100 mg pill, and swallowed them. Oops.
I wasn't sure what might happen. The Rash? A splitting headache? Hypomania? Wandering lung?
Turns out it was nothing dramatic. I felt somewhat dizzy when I stood up after eating breakfast (in a way that's different from the usual head-rush feeling that the medical community has labeled "orthostatic hypotension" for our convenience), but it went away pretty quickly. There was the aforementioned tachycardia, which also went away, and hasn't returned, even though I had to visit the dentist today, and I really HATE that.