40-year-old Ms. Wang is an ordinary white-collar worker in the company, 1 year ago, after eating a large number of fish and shrimp in a seaside team building organized by the company, a flaky red rash suddenly appeared all over the body, mainly in the limbs, there were a lot of small red bumps, accompanied by itching, because Ms. Wang always subconsciously kept scratching, and soon scratched the rash, and a small amount of white exudate oozed after the rash broke. Since Ms. Wang did not carry the medicine with her at that time, the red rash had almost subsided after the team building, and Ms. Wang did not pay much attention to it.
A week ago, Ms. Wang and her family enjoyed the flowers in the park, and soon after returning, Ms. Wang found that there were a few small red rashes on her limbs, and from time to time there was an itching sensation. Ms. Wang thought it would be the same as usual, and it would not take long for it to subside on its own. I never thought that this time the rash not only did not reduce, but became more and more serious.
At first, the rash was only on the distal extremities, but soon it gradually spread upwards and became larger and larger, and the rash the size of a fingernail gradually merged into a single piece, accompanied by intense itching, especially at night, and Ms. Wang even couldn't sleep because of the itching. The rash did not improve with bleeding and oozing after scratching, which made Ms. Wang miserable.
After observing Ms. Wang's skin lesions, the doctor prescribed a series of tests such as blood routine, specific IgE testing, and allergen testing, and found that the proportion of white blood cells and eosinophils in Ms. Wang's body was significantly increased, and the serum total immunoglobulin E was increased, and the allergen test showed that Ms. Wang was allergic to allergens such as pollen, fish and shrimp, and dust mites. Ms. Wang was diagnosed with atopic dermatitis, and the doctor advised her to use topical calamine lotion, oral levocetirizine and other drugs for anti-itching and anti-allergic treatment.
Ms. Wang took the medicine and asked the doctor puzzled: "What is the difference between levocetirizine and the common cetirizine? I think loratadine is also quite commonly used, what is the difference between it and cetirizine?"
The doctor explained with a smile: "In fact, loratadine and cetirizine are both second-generation antihistamines, which can be regarded as 'brothers', while levocetirizine and cetirizine are closer, they are different structures of the same drug." In general, there is not much difference between their efficacy, and their main differences are in adverse reactions, metabolic pathways, onset time, and so on. ”
How do anti-allergy drugs such as loratadine, cetirizine, and levocetirizine work? What diseases can they usually be used to treat? What are the differences between them in terms of adverse reactions, metabolic pathways, onset time, age of use, etc.? We have a detailed understanding of the following contents, understand these points, and use them with more peace of mind!
1. How do loratadine, cetirizine and levocetirizine exert anti-allergic effects?
There are many common anti-allergy drugs, including antihistamines, antileukotrienes, glucocorticoids, etc., loratadine, cetirizine, and levocetirizine are all antihistamine allergy drugs.
When the human body is stimulated by external inflammation, it stimulates mast cells to produce histamine, and the combination of histamine and related histamine receptors will lead to capillary constriction, smooth muscle spasm, increased secretions, etc., which in turn makes the body produce allergic reactions, such as runny nose, redness, swelling and itching of the skin, laryngeal edema, etc.
There are 4 kinds of histamine receptors in the human body, named H1, H2, H3 and H4, H1 receptors are mainly distributed in the vascular endothelium and smooth muscle surface of the skin and mucous membranes, and antihistamines specifically block the pathway of binding histamine and H1 receptors, blocking the key links of allergic reactions, so as to alleviate the effect of allergic reactions in the skin and mucous membranes. Antihistamines are divided into first-generation and second-generation drugs according to the characteristics of their effects.
First-generation antihistamines not only act on H1 receptors, but also interfere with cholinergic and dopamine receptors, have high fat solubility, and can penetrate the blood-brain barrier, so they will bring strong sedative and drowsy effects. Loratadine, cetirizine, levocetirizine, etc. belong to the second-generation antihistamines, which act on the H1 receptor and have higher selectivity, avoiding the risks brought by the first-generation histamine, with higher safety and more clinical use.
In other words, anti-allergy drugs such as loratadine, cetirizine, and levocetirizine exert anti-allergic functions by blocking histamine H1 receptors, so what diseases are commonly used to treat such drugs?
2. What are the indications for these anti-allergy drugs and how to choose?
Clinically, antihistamine allergy drugs mainly block type I hypersensitivity reactions and allergic reactions caused by histamine release, such as allergic rhinitis, urticaria, allergic asthma, etc.
1. Allergic rhinitis
Allergic rhinitis is one of the common indications of second-generation antihistamines, and the onset of allergic rhinitis is mostly the activation of inflammatory cells in the body after the body is exposed to allergens, which in turn leads to the secretion of histamine and other inflammatory factors by the nasal mucosa, with nasal congestion, itching, sneezing, runny nose and other symptoms as the main manifestations.
Because loratadine or cetirizine relieves allergic reactions by blocking histamine receptors, they are commonly used drugs for allergic rhinitis. It is important to note that allergic rhinitis does not cause systemic reactions like other diseases, the lesions are usually confined to the nasal cavity, and oral antihistamines are not necessarily the best choice.
2. Vesaria
Oral antihistamines can also effectively alleviate urticaria, when the allergen stimulates the skin mucosa to produce histamine and other factors, a small area of edema on the skin will appear red flaky wheal, inflammatory substances stimulate the peripheral nerves under the skin will appear itching, oozing and other manifestations, such patients can obtain good efficacy whether they choose loratadine or cetirizine.
Although the safety of this type of drug is high, it is not recommended to take it in excess for a long time, as long-term use is likely to cause adverse reactions such as drowsiness and dizziness, and antihistamines can only relieve symptoms, and long-term use is easy to develop drug resistance.
3. Allergic asthma
Cetirizine and levocetirizine are effective in relieving allergic asthma. Cetirizine is effective in relieving asthma symptoms by relieving spasm and airway hyperresponsiveness of bronchial smooth muscle caused by allergic asthma. However, loratadine is not applicable, which may be related to the fact that loratadine does not directly affect the respiratory mucosa.
In recent years, cetirizine has been included in the guidelines for the prevention and treatment of allergic asthma, but it is mainly used as adjuvant therapy to alleviate the symptoms of mild asthma, and it is not the first choice.
It can be seen that in terms of indications for use, loratadine, cetirizine, and levocetirizine are relatively similar, and can be used for the treatment of allergic rhinitis and urticaria, but cetirizine has certain advantages in the treatment of allergic asthma. So, what are the differences between them?
3. What is the difference between the same anti-allergy drugs? Understand these 4 points and use them with more peace of mind!
Loratadine, cetirizine and levocetirizine all belong to the second generation of antihistamines, their efficacy is similar, but there are subtle differences, mainly in four aspects: adverse reactions, metabolic pathways, onset time and age of use.
1) Adverse reactions are different
The above three drugs have a similar mechanism of action, and overdose may cause adverse reactions such as headache, heart palpitations, and dry mouth. Comparatively speaking, the sedative effect of cetirizine is stronger than that of loratadine, because cetirizine can act on the nerve center, so dangerous operations such as driving, high-altitude, and machinery should be avoided as much as possible during taking the drug. In addition, loratadine is metabolized by the liver, and cetirizine and levocetirizine are excreted through the kidneys, so taking loratadine is more likely to cause liver damage, jaundice, hepatitis and other liver adverse reactions. During the period of taking the drug, attention should be paid to the observation of adverse reactions, and if there is any abnormality, the drug should be stopped in time.
2) Metabolic pathways are different
The difference in metabolic pathways is one of their biggest differences. As mentioned earlier, loratadine is metabolized by the liver, and cetirizine and levocetirizine are metabolized by the kidneys. There are a large number of liver enzymes in the liver, and loratadine is mainly catabolized by CYP3A4 and CYP2D6, two liver enzymes, therefore, the combination of CYP3A4 and CYP2D6 inhibitors, such as clarithromycin, fluoxetine, etc., will interact, resulting in an increase in blood concentration, increasing the generation of adverse reactions, and should be avoided when taking it with other drugs. Cetirizine and levocetirizine do not have this disadvantage, and the probability of drug interactions is very low.
3) The onset time is different
They also do not have the same onset of action, with loratadine having a slower onset of action than cetirizine and levocetirizine. Generally speaking, it takes 1~3 hours to see the effect after taking loratadine, while cetirizine can take effect in about half an hour.
Levocetirizine is the main active ingredient of cetirizine, which can be directly used without absorption and transformation after taking it, and the onset time is better than that of cetirizine. However, although cetirizine has a rapid onset of action, its half-life is shorter than loratadine, which means that loratadine has a longer duration of action and can be taken once a day, while cetirizine is best used once in the morning and once in the evening.
4) The age of use is different
The age at which the above three drugs are used is also different. Studies have shown that loratadine may be cardiotoxic, so it is suitable for children over 2 years of age. The relevant clinical studies of cetirizine and levocetirizine showed that the minimum age of use was 6 months.
At present, there is no reliable research to prove that the above anti-allergy drugs can directly cause damage to children's health, but no matter what kind of drug, you should be cautious when using drugs for infants and children, and it is best to consult a doctor before use, and do not use drugs blindly!
Loratadine, cetirizine and levocetirizine are all antihistamine allergy drugs, with similar efficacy, and can be used to treat histamine-induced rhinitis and skin allergic diseases, but there are still big differences in adverse reactions, metabolic pathways, onset time and age of use, etc., and the drug should be carefully selected according to their own conditions in daily life. For the sake of drug safety, it is recommended that you do not buy it blindly under the guidance of your doctor!
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