What is the Difference Between Cetirizine and Loratadine

The key difference between Cetirizine and Loratadine is that Cetirizine relieves allergy symptoms within one hour after oral administration with more sedative effects, while Loratadine may take three hours to relieve allergy symptoms with less sedative effects.

Cetirizine and Loratadine are two second-generation antihistamines used to treat allergy symptoms. They block the effect of histamine, a chemical messenger released during allergy reactions. They help to relieve symptoms such as sneezing, runny nose, itchy eyes, and hives. In most countries, both these medications are available over the counter without a doctor’s prescription. Cetirizine and Loratadine are generally safe for most people. However, they can cause side effects like drowsiness, dry mouth, and headache.

CONTENTS

1. Overview and Key Difference
2. What is Cetirizine 
3. What is Loratadine
4. Similarities – Cetirizine and Loratadine
5. Cetirizine vs. Loratadine in Tabular Form
6. Summary – Cetirizine vs. Loratadine

What is Cetirizine?

Cetirizine or Zyrtec is an orally available second-generation histamine H1 antagonist primarily prescribed to control allergic rhinitis and chronic urticaria. The clinical significance of Cetirizine in allergy respiratory diseases has been well studied. The main effect of Cetirizine is achieved through the selective inhibition of peripheral H1 receptors. It does not readily cross the blood-brain barrier, so no significant effect has been shown with cerebral H1 receptors.

Cetirizine is absorbed well after oral administration as tablets or syrups, with a maximum concentration within 1 hour. It has no proven food effect, while 93% of the absorbed drugs remained bound with plasma proteins. Cetirizine is partially metabolized in the liver and mainly excreted in the urine with a half-life of 8.3 hours. Cetirizine is generally safe for most people, but it can cause some side effects, such as drowsiness, dry mouth, and headache.

What is Loratadine?

Loratadine is another second-generation antihistamine used to manage allergic rhinitis symptoms. In addition, Loratadine is used to treat wheal formation, urticaria, and other allergic dermatologic conditions. It is a small molecular drug with no proven adverse effect on the central nervous system. Loratadine is also selective for peripheral H1 receptors and has a poor affinity with the central nervous system H1 receptors. Loratadine does not have CNS depressant effects, such as drowsiness, sedation, and impaired psychomotor function, because it has a poor affinity for CNS H1 receptors and does not penetrate the central nervous system well.

Loratadine is rapidly absorbed and reaches peak plasma concentration within 1-2 hours after oral administration. After the absorption, most of the Loratadine remained bound with the plasma proteins. It undergoes extensive first-pass metabolism in the liver to more pharmacologically active metabolites than Loratadine. The drug is eliminated with urine and feces, with a half-life of 10 hours. Loratadine is also generally considered safe but may cause some side effects, such as insomnia, headache, fatigue, drowsiness, and rash.

What are the Similarities Between Cetirizine and Loratadine?

• Cetirizine and Loratadine are second-generation antihistamines.
• Both are available over the counter in most countries.
• They are effective at relieving allergy symptoms.
• Both drugs have a similar side effect profile, which includes drowsiness, dry mouth, and headache.
• They both have a similar duration of action, which is about 24 hours.

What is the Difference Between Cetirizine and Loratadine?

Cetirizine and Loratadine are second-generation antihistamines commonly used to treat allergy symptoms, such as sneezing, runny nose, itchy eyes, and hives. While they share similar functions, there is a distinct difference between Cetirizine and Loratadine. Cetirizine relieves allergy symptoms within one hour after oral administration with more potency, while Loratadine needs around three hours to relieve allergy symptoms with lesser potency. However, Cetirizine is associated with more sedative effects than Loratadine. The brand names of Cetirizine include Zyrtec, Reactine, and Aller-tec, while Loratadine comes under the brand names Claritin, Alavert, and Diphen.

Below is a summary of the difference between Cetirizine and Loratadine in tabular form for side-by-side comparison.

Summary – Cetirizine vs Loratadine

Cetirizine and Loratadine are second-generation antihistamines used to treat allergy symptoms and are available over the counter in most countries. They are both effective in alleviating allergy symptoms within 24 hours of the duration of action. Both drugs have similar side effect profiles, including drowsiness, dry mouth, and headache. The key difference between Cetirizine and Loratadine includes their onset of action. Cetirizine relieves allergy symptoms within one hour after oral administration, while Loratadine relieves the allergy symptoms within three hours. However, it is essential to talk to a doctor to determine which medication suits the given conditions.

Reference:

1. Curran, Monique P, et al. “Cetirizine.” Drugs, vol. 64, no. 5, 2004.
2. AlMasoud, Najla, et al. “Loratadine.” Profiles of Drug Substances, Excipients and Related Methodology, 2022.

Image Courtesy:

1. “Cetirizine structure” By User:Mysid – Own work Self-made in bkchem; edited in perl. (Public Domain) via Commons Wikimedia
2. “Loratadine” By Harbin – Own work (Public Domain) via Commons Wikimedia