There are basically three different groups medications that are typically used to treat the common cold. Antihistamines, decongestants and expectorants are different types of medications that provide vary different results with the same objective relieving the symptoms of the common cold.
Many cold symptoms are due to the body’s overproduction of histamines. When you get a cold, do you have itchy eyes, redness or swelling? These are common symptoms of body’s overproduction of histamine. The histamines are produced to react to the foreign substances that have entered the body. They are part of the body’s natural defense mechanism. Antihistamines are drugs that are designed to compete for the same receptor sites as histamines. Only one histamine or antihistamine can latch on to a receptor site at a time. If an antihistamine is able to latch on to the receptor site before histamine, the reaction that the histamine usually triggers- itchy eyes, swelling or redness- will not occur.
A runny nose is often a common symptom of a cold. It is caused when the nasal mucous membranes swell in response to the rhinovirus. Decongestants are drugs that are designed to stimulate the alpha-adrenergic receptors to tell the brain to constrict the capillaries within the nasal mucosa. Shrinking the capillaries reduces the amount of fluid that is secreted from the nose, inevitably stopping a runny nose.
The accumulation of mucus in the lungs from a cold or respiratory infection usually becomes thick and difficult to expel. Expectorants are medications that help to loosen the thick mucus secretions making it easier to cough up and expel. Expectorants are capable of increasing the fluid output of the respiratory tract and can decrease the surface tension allowing the mucus easier movement up and out of the respiratory tract.