You probably can, but I'm not sure you'll get any better effect by taking both, as they act on the body in very similar ways.
To your health,
Question...I came down real bad with Allergy and Sinus last week/Friday. I started on Claritin 24hr (Allergy) and Dimetapp Cold and Allergy. I am a heck of alot better now....But was it safe to take them both like I did. I never had any side effects. Now Wednesday, I am only taking the Claritin. My daughter's Pediatrian put her on 2 different Allergy med, which she alternated, He said it was fine.
The physician will always have the final word on mixing any types of medicine, whether they are for the same condition or different conditions. And remember, that each person's response can be slightly different to the same medication. Another great resource when it comes to questions about medication and mixing them is your pharmacist.