If I take Pepto Bismol + Other Med. (e.g., headache, allergy) will the other med work well, or will the Pepto block or absorb the other med somehow, as it coats, soothes, and relieves?
Not in my experience. However, do read the instructions on the label. I think that they advise you to limit aspirin at the same time.
IANAD, this is not medical advice. Read the label.
Drugs.com has a pretty decent summary of contraindications and drug interactions between medication. Here is it’s page on Pepto-Bismol.
Looking quickly, combo medication like cold and allergy meds containing combos of acetaminophen/codeine/pseudoephedrin/guaiafenesin could have CNS and GI effects when mixed with Pepto-Bismol. Straight-up acetaminophen and ibuprofen don’t seem to.
Have a look at the drug you intend to take and see if it’s on the list. It’s not a substitute for the more complete information a pharmacist might be able to give you, and it might not be a complete list of interactions, but it’s a start.