What Is the Connection between Acetaminophen and Diphenhydramine?

Acetaminophen and diphenhydramine are two different types of medications. The connection between acetaminophen, an antipyretic and analgesic, and diphenhydramine, an antihistamine, is that they can be used together to treat illnesses that produce symptoms which are normally relieved by these medications individually. Medical conditions that can be treated with a combination of acetaminophen and diphenhydramine include allergies, the common cold and the flu.

Examining acetaminophen and diphenhydramine separately might further illustrate the connection between using a combination of both medications to treat certain conditions. It is not known exactly how acetaminophen works, but it treats pain and fever by raising a person’s pain threshold and by lowering his or her body temperature. These actions enable the medication to treat backaches, headaches and toothaches, in addition to fever and other types of pain. As an antihistamine, diphenhydramine works by blocking histamine, a chemical that causes allergy symptoms such as runny nose, sneezing and watery, itchy eyes. In addition, diphenhydramine can also treat other symptoms like coughing, insomnia and motion sickness.

Since acetaminophen and diphenhydramine each treat a variety of symptoms and do not interact when combined, it is then possible to use both medications to treat medical conditions that require the relief made possible by both drugs. Although acetaminophen and diphenhydramine work well together, interactions can still occur with other medications. In addition, a person with a medical condition that interacts with either acetaminophen or diphenhydramine might not be able to use a combined form of both medications. Other medications that can interact with the combination include anticoagulants, beta blockers and monoamine oxidase inhibitors (MAOIs). Medical conditions that also might interact with acetaminophen and diphenhydramine include alcoholism, an enlarged prostate and problems with the liver.

Taking acetaminophen and diphenhydramine separately can cause side effects to occur, and the same can be said of taking both medications together as well. As with all medications, there is always the possibility of an allergic reaction to the medication itself. Other side effects include constipation, drowsiness and excitability, in addition to more serious side effects which include abnormal urination, irregular heartbeat and jaundice. Usually, mild side effects do not necessarily require medical attention while serious side effects require immediate medical attention but sometimes less serious side effects can persist or worsen over time. If this occurs, the affected person should contact his or her doctor.