NSAIDs decrease the effectiveness of aspirin.
Tylenol ads now caution about taking ibuprofen with aspirin.
Lots of patients on low-dose aspirin for heart disease also take ibuprofen for pain, fever, arthritis, etc. But several studies suggest that ibuprofen might blunt aspirin's beneficial antiplatelet effects.
This all started back in 2002 when a small study suggested that ibuprofen might blunt aspirin's antiplatelet effects.