For future reference:

Leave the medicinal chemistry to those who know what their doing.

My thinking: They make Claritin with a decongestant in it as well. I only have the regular generic. I am having a problem with congestion as well, mostly at night. Therefore, I will buy some Sudefed, and just take that before I go to bed.

Technically my logic was correct and for several hours I did not suffer a stuffy nose. I did not sleep, either. The allergy pills alone have been making me sleep fitfully at best; the Sudefed did not improve that. I dozed off and woke up in a state of absolute panic and, for a few moments, was convinced I was having a heart attack. I just sat there, trying not to hyperventilate, for probably an hour. Eventually I started dozing back off, only to have some noise (neighbors or something) wake me and repeat the cycle. I'm also fairly certain I was having some aural hallucinations, which just made me feel even more paranoid. Whee.

So...no more pharmaceutical mix-and-matching for me. Fun experiment but I think I've learned a valuable lesson about oh god never again.