Difference Between CPM and Cetirizine

An allergy is a condition where the immune system of the body reacts abnormally against a foreign substance. There are many types of allergies such as food allergy, drug allergy, animal allergy, etc.


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Most types of allergies are not typically harmful to mankind and can be treated with medicines or drugs specifically curated to treat different types of allergy.

Allergies can be very minor or severe depending upon the type of allergen. The most common symptoms of allergy include but not limited to skin rashes, patches of redness in the skin, inflammation of the skin, watery eyes, itching, sneezing, running nose, etc.

The common symptoms of allergy are generally termed as Allergic Rhinitis. Many drugs are used to treat this condition and the two most common types are – Chlorphenamine or Chlorpheniramine, also known as CPM and Cetirizine.

CPM vs Cetirizine

The difference between CPM and Cetirizine is that CPM is an antihistamine used for treating the allergic conditions, and it takes action within six hours of use. Cetirizine is a second-generation antihistamine also used for treating allergic conditions, and it takes action within an hour of use.

CPM vs Cetirizine

Both CPM and Cetirizine belong to the second generation of Antihistamines and are generally available over-the-counter (OTC) and can be taken by mouth in a tablet form. Antihistamines of the second generation will not cause as much drowsiness as compared to the first generation.


Comparison Table

Parameter of ComparisonChlorphenamineCetirizine
ChemistryIt is an alkylamine and exhibits optical isomerismIt consists of stereo-isomers of types L and D
SynthesisSynthesis is done in the presence of an inorganic compound called sodium amide (NaNH2)Synthesis is done in the presence of an inorganic compound called sodium carbonate (Na2CO3) and an isomer called xylene (C8H10)
Half-lifeIn adults, the half-life of elimination ranges from 13.9 to 43.4 hoursIn adults, the half-life of elimination ranges between 6.5 and 10 hours
Side EffectsSide effects include but not limited to dry mouth, dizziness, constipation, nauseaSide effects include but not limited to headache, drowsiness, fatigue
Drug AdministrationIt can be administered either by mouth or intravenous or intramuscular or as subcutaneous injections depending on the condition and requirement of an individualIt can be administered only by mouth in the form of capsule or tablet or syrup


What is Chlorphenamine?

Chlorphenamine is also known as Chlorpheniramine or CPM and it is a type of Antihistamine drug used to treat different types of allergies such as Allergic Rhinitis. It is available as a generic medicine and also over-the-counter.

The use of CPM came into existence for use in the medical field in the year 1949. It does not pose any risk to an individual when administered in prescribed quantities by a physician. Despite this, many common side effects are found to occur.

CPM has a molecular formula of C16H19ClN2 and acts as a powerful inverse agonist of the histamine H1 receptor. It is synthesized using pyridine in the presence of sodium amide by hydrolysis and decarboxylation process.

It is commonly sold under the drug name of Chlortrimeton and Piriton. The general side effects observed after administering CPM in individuals are dry mouth, dizziness, anxiety, constipation, and nausea. 


What is Cetirizine?

Cetirizine is a type of Antihistamine drug used to treat Allergic Rhinitis and is predominantly used in the treatment of Hay’s fever and chronic Hives disease. It belongs to the second generation of antihistamines and is available over-the-counter and also as a generic medicine for consumption.

The use of Cetirizine came into existence for use in the medical field in the year 1987. It works by blocking the histamine H1 receptor and acts as a selective antagonist.

Cetirizine has a molecular formula of C21H25ClN2O3 and is synthesized in the presence of sodium carbonate and xylene by the saponification process and yields a product of carboxylic acid.

It is generally sold under the drug name as Zyrtec and Incidal. The most common side effects reported by the individuals after consuming cetirizine are fatigue, drowsiness, headache, and aggression.

We need to store this Cetirizine at room temperature and avoid excessive heat and moisture. Keep it away from children and preserve it in the same tightly closed container it came in. 


Main Differences Between CPM and Cetirizine

  1. Both Chlorphenamine (CPM) and Cetirizine produce effective results in treating allergic rhinitis and other similar conditions. The main difference between Chlorphenamine and Cetirizine is the chemical composition and the process of synthesizing inorganic compounds of both the drugs.
  2. The bio-availability of Chlorphenamine is 25% to 50% whereas the bio-availability of Cetirizine is well above 70%.
  3. The onset of action of Chlorphenamine is within 6 hours but Cetirizine begins the onset of action generally within 1 hour. However, the effect of both drugs remains for 24 hours.
  4. The capacity of binding of protein in Chlorphenamine is 72% whereas the capacity of binding of protein ranges from 88% to 96% in Cetirizine.
  5. In the case of Chlorphenamine, the half-life of elimination in adults who are found to be healthy ranges from 13.9 hours to 43.4 hours but in the case of Cetirizine, it ranges from 6.5 hours to 10 hours.


  1. https://onlinelibrary.wiley.com/doi/pdf/10.1288/00005537-198906000-00006
  2. https://pubs.rsc.org/en/content/articlehtml/2014/ay/c3ay41698d
  3. https://www.jacionline.org/article/0091-6749(92)90083-E/pdf
  4. https://www.hindawi.com/journals/jspec/2011/291720/abs/
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