Chlorpheniramine is a histamine-1 (H₁) antagonist or antihistamine medication used to treat upper respiratory tract conditions. It provides temporary relief of symptoms such as runny nose, sneezing, and itchy eyes, nose, or throat associated with hay fever/allergic rhinitis (Facts and Comparisons, 2023). How does it work?

How Does Chorpheniramine Work?

Although chlorpheniramine can’t reverse symptoms of an allergic response, treat the cause, or expedite recovery, it can stop the progression of the response. Here’s what happens.
 
When sensitized to an antigen, a mast cell reacts to repeated antigen exposure by releasing chemical mediators. One of these mediators, histamine, binds to H₁ receptors found on effector cells (the cells responsible for allergic symptoms). This initiates the allergic response that affects the respiratory, cardiovascular, gastrointestinal (GI), endocrine, and integumentary systems.
 
Chlorpheniramine competes with histamine for H₁-receptor sites on the effector cells. By attaching to these sites first, the drug prevents more histamine from binding to the effector cells and the systemic allergic responses are stopped. It will halt the progression of symptoms such as bronchial constriction and bronchospasm, itchy nose and throat, rhinorrhea, sneezing, hypotension, increased heart rate, vasodilation, hives, swelling, and general flushing of the skin.

Examples of Chlorpheniramine

You may be familiar with common brand names of chlorpheniramine such as Aller-Chlor, Allergy, Allergy Relief, Chlor-Trimeton, Chlor-Trimeton Allergy, ChlorHist, Diabetic Tussin Allergy, Ed Chlorped Jr, and Pharbechlor. When these drugs are used over-the-counter (OTC) for self-treatment, advise the patient to notify a health care provider prior to use if they have breathing problems (i.e. chronic bronchitis, emphysema), glaucoma, an enlarged prostate, or are currently taking sedatives or tranquilizers (Lexicomp, n.d.).

Nursing Considerations (Facts and Comparisons, 2023)

The usual chlorpheniramine dose for adults and children over 12 years of age is 4 mg (immediate release) every 4 to 6 hours or 12 mg (extended release) every 12 hours for a maximum dose of 24 mg per 24 hours. The U.S. Food and Drug Administration (FDA) does not recommend the use of chlorpheniramine in infants and children under the age of 2 years due to life-threatening adverse events such as metabolic acidosis, seizures, renal failure, and central nervous system (CNS) depression. The FDA cautions the use of chlorpheniramine in pediatric patients greater than 2 years of age. For children 6 years to under 12 years of age, the usual dose is 2 mg  (immediate release) every 4 to 6 hours with a maximum daily dose of 12 mg per 24 hours. There is no recommended extended release dose for pediatric patients under 12 years of age.
 
Timed release oral forms should be swallowed whole, not crushed or chewed. Advise patients that chlorpheniramine may cause CNS depression and caution should be taken when peforming tasks that require mental alertness such as operating machinery or driving. Note: these antihistamines can cause excitation in pediatric patients.
 
For complete information, please consult the drug’s specific package insert or the Nursing2022 Drug Handbook® + Drug Updates.

References
 
Facts and Comparisons (2023, March 3). Chlorpheniramine Oral. https://fco.factsandcomparisons.com/lco/action/doc/retrieve/docid/fc_dfc/5549065?cesid=0IQwU9D6dfT
 
Lexicomp (n.d.). Chlorpheniramine: Drug Information. UpToDate. Retrieved April 11, 2023 from https://www.uptodate.com/contents/chlorpheniramine-drug-information?topicRef=7526&source=see_link