What are the differences between cetirizine, loratadine and montelukast in treating allergies?

The climate in autumn is dry and the air humidity is low. The human skin and mucous membranes are more likely to lose moisture and become dry, forming tiny cracks. External pathogenic substances can easily invade the skin and irritate the human body. Therefore, autumn is a season when allergic diseases are prevalent. A reader friend left a message to Huazi, saying that cetirizine, loratadine and montelukast are all commonly used drugs to treat allergic symptoms. What are the differences between them?

1. Cetirizine and loratadine are antihistamines. In terms of pharmacological classification, although cetirizine and loratadine are different in chemical structure, their pharmacological actions are similar. They are both antihistamines that can antagonize allergic reactions caused by histamine. Therefore, their indications are basically the same, and they can both relieve symptoms of the skin, eyes, and nose caused by allergies. However, cetirizine can be used for allergic asthma, while loratadine does not have this indication.

Cetirizine has two optical isomers, one is "levorotatory" and the other is "dextrorotatory". This is like the left and right hands of a person, although they have the same structure, they are opposite in spatial arrangement. Levocetirizine has higher selectivity and less side effects of causing drowsiness, and is now more commonly used.

Although the side effect of ordinary cetirizine is greater, it has a wider range of therapeutic effects on allergic diseases. For patients who have poor results with levocetirizine, switching to ordinary cetirizine may still be effective.

After loratadine enters the human body and is metabolized, it produces desloratadine, which has stronger antihistamine activity and fewer side effects. Therefore, people extract desloratadine separately and make it into medicine in order to achieve stronger effects and fewer side effects.

2. Montelukast is a leukotriene receptor blocker. Various cells in the human body can release leukotrienes, which are potent inflammatory mediators that can bind to leukotriene receptors, causing airway smooth muscle contraction, increased vascular permeability, and increased mucus secretion. It plays an important role in inflammation, asthma, and allergic reactions.

Montelukast can compete with leukotrienes for binding receptors, but will not produce an agonist effect. It can alleviate asthma and allergic reactions caused by leukotrienes, and is mainly used for asthma and alleviating symptoms caused by allergies. However, the onset of action of blocking leukotriene receptors is very slow, and it takes 4 weeks of continuous application to see the effect. Therefore, Montelukast is not recommended for acute attacks of asthma or allergies, and is usually used as a preventive and long-term medication.

3. Pay attention to the time of medication when you are allergic. When treating allergic diseases, cetirizine and loratadine cannot directly block the binding of histamine to receptors, but compete with histamine for receptors and have no effect on histamine that has already bound to receptors. In other words, antihistamines have no effect on allergic symptoms that have already occurred, but can prevent the occurrence of subsequent allergic symptoms.

Therefore, for seasonal allergic diseases whose onset can be predicted, it is necessary to start taking antihistamines 1 to 2 weeks in advance for prevention, rather than waiting until allergic symptoms occur. As for leukotriene receptor blockers, because they take a long time to take effect, they need to be taken a month in advance.

4. Pay attention to safety when taking medicines. Cetirizine and loratadine are over-the-counter drugs and can be purchased and used by yourself. However, levocetirizine, desloratadine and montelukast are prescription drugs and need to be purchased and used under the guidance of a doctor and with a doctor's prescription.

Antihistamines have more or less the side effect of causing drowsiness. When treating allergic diseases, cetirizine and loratadine have similar efficacy and can replace each other. The former is slightly stronger than the latter, and the side effect of drowsiness is also slightly stronger than the latter. However, if you need to drive a vehicle or operate machinery and other dangerous work, it is recommended to choose loratadine.

Cetirizine is mainly excreted by the kidneys and does not need to be metabolized by the liver, while loratadine and montelukast need to be metabolized by the liver. Therefore, people with poor kidney function should be cautious when taking cetirizine, and people with poor liver function should be cautious when taking loratadine and montelukast.

For pregnant women and children under 2 years old, these three drugs are not absolutely safe and should be avoided as much as possible. Or, when the benefits of the drug outweigh the risks, they can be used with caution under the guidance of a doctor.

These three drugs are not suitable for acute allergies or acute asthma attacks, so people with acute allergies need to seek medical attention promptly. People with asthma need to carry a fast-acting antiasthmatic aerosol with them in case of emergency.

In conclusion, this article is only to illustrate the pharmacological effects and differences of these three anti-allergic drugs, and cannot be used as a basis for medication. In order to ensure the safety and effectiveness of medication, the drugs should be used under the guidance of a doctor, and if any problems are found, consult a doctor or pharmacist in time. I am pharmacist Huazi, welcome to follow me and let me be the pharmacist by your side.