Neither Sudafed Sinus & Headache Caplets or Sudafed Sinus & Headache Maximum Strength Tablets contains an antihistamine, actually. They both contain pseudoephedrine, which is part of a class of drugs called sympathomimetic agents--they are used for nasal decongestants. Acetaminophen is a pain medication.
However, Sudafed Sinus Nighttime Plus Pain Relief Caplets do contain an antihistamine called Diphenhydramine Hydrochloride.
However, Sudafed Sinus Nighttime Plus Pain Relief Caplets do contain an antihistamine called Diphenhydramine Hydrochloride.