Health Canada initiated a safety review following a report by the European Medicines Agency about the potential drug-drug interaction between phenylephrine and acetaminophen. These drugs are often found together in over-the-counter health products including those for treating cold, flu and allergies. People who have high blood pressure or heart disease may be more vulnerable to the side effects of phenylephrine if both of these drugs are taken together as there appears to be an interaction between them that leads to an increase of phenylephrine in the body (increased bioavailability).