Recently, sneezing, nasal congestion, itchy nose...... In order to alleviate the symptoms, many citizens urgently took out "loratadine tablets", and today's #loratadine# topic is on Weibo's hot search, causing everyone to watch.
Screenshot of Weibo
In addition to loratadine, many netizens pointed out in the Weibo comment area that "cetirizine" can also be anti-allergic, which also caused some netizens to wonder, what is the difference between loratadine and cetirizine?
Loratadine and cetirizine
What exactly is the drug?
Loratadine and cetirizine are both antihistamines, and in addition to being anti-allergic, these drugs can also be used for urticaria, allergic conjunctivitis, and obvious itching after mosquito bites.
When we have hives, allergic rhinitis, etc., the body's immune system will release a substance called "histamine", which then binds to the histamine receptors in the body, which will cause us to have itching, sneezing, runny nose and other discomforts.
Antihistamines, as the name suggests, are drugs that block the binding of histamine to receptors, preventing histamine from working.
More than 100 years ago, scientists discovered histamine and soon discovered its role in allergic reactions. Regarding antihistamines, Italian pharmacologist Daniel Bovet discovered the first synthetic compound with antihistamine effect, which could protect guinea pigs from histamine-induced allergic reactions, but because of the toxicity of the compound, it was not used in clinical practice, but laid the foundation for the later development of antihistamines.
Antihistamines ≠ allergy medications
Antihistamines refer to drugs that prevent histamine from working, histamine is not only involved in allergic reactions, but also in the occurrence of other diseases, so antihistamines may be used in other situations except for allergies.
Anti-allergic drugs, there is no such classification in pharmacology, usually a summary of many drugs, refers to the drugs used in allergies, in addition to histamine, allergic reactions will also have other substances in the body involved, and the drugs selected in different situations are also different, such as anaphylaxis will be treated with epinephrine first.
However, because we often use antihistamines when we have allergy symptoms, we mistakenly equate antihistamines with allergy drugs, but in fact, they only have some overlap.
What are the antihistamines?
There are currently 4 types of histamine receptors found in the body, including H1, H2, H3, and H4. To help us relieve our symptoms, antihistamines target these receptors so that histamine doesn't work. Thereinto:
· H1 antihistamines are antihistamines that we often discuss and use, mainly for hives, allergic rhinitis, etc., including cetirizine, loratadine, etc.;
· H2 antihistamines (e.g., cimetidine, etc.) are mainly used for peptic ulcer disease and gastroesophageal reflux disease;
· Many H3 antihistamines are in clinical trials, and there is currently tilolison approved for narcolepsy;
· H4 antihistamines are still in clinical trials.
Because H1 antihistamines are the most abundant and the most common ones we are exposed to in treatment, today we will briefly learn about H1 antihistamines.
Note: Unless otherwise stated, antihistamines are referred to as H1 antihistamines.
H1 antihistamines
H1 antihistamines are currently divided into two categories, first-generation H1 antihistamines and second-generation H1 antihistamines.
First-generation H1 antihistamines, common ones are diphenhydramine, chlorpheniramine, etc.
· Poor selectivity for H1 receptors (in addition to finding H1 receptors, they will also find trouble with other receptors);
· It is easy to penetrate the blood-brain barrier (refers to a structure between blood and brain tissue, which can block some substances from entering the brain tissue and play a protective role), causing drowsiness, fatigue, dizziness and other adverse reactions, and is a class of antihistamines with sedative effect;
· It will have an anticholinergic effect, which may cause blurred vision, dry eyes, nose and mouth, urinary retention, constipation, etc.;
· It is usually given multiple times a day.
As a result, first-generation antihistamines are no longer the preferred antihistamines for urticaria and allergic rhinitis. However, in the case of motion sickness (motion sickness), first-generation antihistamines (e.g., diphenhydramine, dimenhydrinate, etc.) are preferred, while non-sedating second-generation antihistamines are not recommended.
Second-generation H1 antihistamines, common ones are cetirizine, loratadine, olopatadine, etc.
· Highly selective for H1 receptors (basically only looking for H1 receptors, rarely bothering other receptors);
· It is not easy to penetrate the blood-brain barrier, and the sedative effect is weak;
· There were no significant anticholinergic adverse effects;
· It can usually be given 1 dose per day.
Overall, there are fewer adverse reactions, antihistamines are recommended for urticaria, allergic rhinitis, and second-generation antihistamines can also be used if there is significant itching after mosquito bites.
Cetirizine and loratadine
What's the difference, exactly?
Cetirizine and loratadine are both commonly used second-generation antihistamines, but they are different classes of compounds, although there is not much difference in efficacy and safety.
There have been some small studies that have found that cetirizine improves symptoms better than loratadine in allergic rhinitis and mosquito bite relief treatments, but is more likely to have sedative effects (such as drowsiness) than loratadine.
There are no data to suggest which drug is more effective for acute urticaria, and several studies of chronic urticaria suggest that cetirizine and levocetirizine may be slightly more effective than other agents.
Cetirizine vs loratadine, which is better?
No one has been found to be optimal, but combined with the current evidence, it can be used according to the appropriate age and dose (see below for recommendations for children, pregnant and lactating women) and according to the doctor's advice if the indication for use is met.
In addition, due to individual differences in medications, if one of them is not effective, or if there are obvious adverse reactions, treatment with another drug may be considered.
What should I pay attention to when using antihistamines?
Although antihistamines are used in many diseases, the use of drugs is a decision to weigh the pros and cons, and it needs to be used in combination with specific populations, diseases, etc.
When using antihistamines, we can pay attention to the following:
1
Different diseases may have the same symptoms
The same symptoms every time you have are not necessarily the same disease, such as allergic rhinitis, common cold, sneezing, runny nose, etc.
In the case of allergic rhinitis, antihistamines may be used to relieve symptoms. However, the common cold is not recommended because antihistamines are not effective in relieving the nasal symptoms of the common cold. Therefore, when symptoms appear, the cause should be analyzed first, and then medication should be considered.
2
The same disease may have different causes and pathogenesis
Allergic rhinitis and hives may use antihistamines.
For allergic rhinitis, although antihistamines often reduce itching, sneezing, and rhinorrhea, they are not as effective as glucocorticoid sprays for nasal congestion (nasal congestion). Therefore, glucocorticoids are recommended for patients with chronic symptoms, more severe symptoms, or if antihistamines have adverse effects and prefer topical therapy.
Not all antihistamines are effective in urticaria, such as acute urticaria caused by Mycoplasma pneumoniae infection, in which case anti-infective drugs such as azithromycin may be considered. Therefore, even if you have had a disease before, you should take medicine according to the specific situation this time.
3
Second-generation antihistamines are generally well safe and well tolerated
Although second-generation antihistamines are generally well safe and tolerated. However, the determination of the course of treatment and dose needs to be comprehensively evaluated according to the type of disease and the change of the condition, and do not stop the drug or increase the dose at will during the process, so as not to delay the treatment or increase the probability of adverse reactions.
4
Medication recommendations for children
In addition to the indication for disease, children need to be aware of the appropriate age and dose, such as cetirizine and loratadine at the appropriate age and dose:
· cetirizine:
≥ 6 years: 10 mg once daily
2 to 5 years: 5 mg once daily
6 months to 2 years: 2.5 mg once daily
· loratadine:
≥ 6 years: 10 mg once daily
2 to 5 years: 5 mg once daily
There may be some differences in the package insert, such as:
· In some instructions, cetirizine is suitable for a minimum age of 1 year, and some suggest that it should be used with caution between 6 months and 1 year old;
· In some instructions, loratadine is referred to at a different age, and the reference dosage is > 12-year-old children: 10 mg once a day. Weight is required for ages 2 to 12 years, > 30 kg: 10 mg once a day, ≤ 30 kg: 5 mg once a day. If both age and weight are considered, it is prudent to choose a low dose.
When choosing a dosage form, according to different age groups, you can choose an appropriate dosage form to improve children's compliance with medication, for example, young children can give priority to liquid dosage forms, which is convenient to take and administer, which is better than granules and dispersible tablets. In addition, young children with poor swallowing ability should avoid using capsules.
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5
Recommendations for pregnant and lactating women:
Cetirizine or loratadine may be preferred during pregnancy and lactation, and there are reassuring data on the use of both drugs in a large number of pregnant patients. Both drugs are also rarely secreted into breast milk and usually do not cause sedation or feeding difficulties in infants.
Although evidence-based databases consider these two drugs to be relatively safe, some drug labels mention that cetirizine is not recommended for use during pregnancy and lactation, while loratadine usually recommends caution during pregnancy and lactation.
Because the scope of application of approved drugs in different countries and regions may be different, and the dosage of drugs for different diseases or with obvious renal function and/or liver insufficiency may also be different, you can consult a doctor or pharmacist for specific medication problems.