Most drugs, including aspirin, can be used with the approval of a physician. Drugs that induce hypertension are not a good idea. Aspirin can be used when blood vessels are narrowed by a dissection, particularly in vessels that feed the brain, to maintain flow. So there is never a never with medications and it is always a matter of appropriate care.
Taken from the Q & A's on the EDNF board - answered by Peter Byers, MD and Melanie Pepin, MS, CGC