Is it safe to take pseudophedrine and diphenhydramine together? medscape says significant interaction but other sources say no interaction.

Yes: One is a decongestant, the other is an antihistamine. Pseudophedrine can cause a slight BP increase, and dryness. Diphenhydramine can be sedating. The two (or meds from the same class) are commonly mixed in OTC cough and cold remedies.

OK to take together: Diphenhydramine is benadryl, (diphenhydramine) which is an antihistamine. Many antihistamines are taken together with decongestants such as pseudoephedrine. Diphenhydramine can help itching, sneezing, swelling, whereas Pseudoephedrine can help nasal congestion. Common antihistamine/decongestant combos include loratadine-D, cetirizine-D, fenofexadine-D.