Chlorpheniramine
[Overview]
The molecular formula of chlorpheniramine is C20H23N2ClO4, and its molecular weight is 390.85. The scientific name is chlorpheniramide maleate. White crystalline powder. No odor and bitter taste. Melting point 130~135℃. It is soluble in water, ethanol and chloroform, and the aqueous solution is acidic. It is easy to deteriorate when exposed to light. It can be obtained by condensing pyridine, p-chlorotoluene and diformamide and then treating it with maleic acid. [1]
Chlorpheniramine is one of the strongest antihistamines with long-lasting effects, low dosage, and few side effects. It mainly can competitively block the histamine H1 receptor on allergic target cells, so that histamine cannot bind to the H1 receptor, thereby inhibiting the allergic reaction caused by it. Suitable for various allergic diseases, drug allergic reactions, etc. Oral absorption is rapid and complete, with low incidence of adverse reactions. The sedative effect is weaker than that of promethazine, and it also has certain anticholinergic effects. It is similar to diphenhydramine but has less central depressant effects. Can induce epilepsy and is contraindicated in patients with epilepsy. Use with caution in lactating women, patients with glaucoma, hypertension, hyperthyroidism, and prostatic hypertrophy. While taking the medicine, you are not allowed to drive cars, boats, airplanes and other motor vehicles or operate machinery.
Chlorpheniramine has many central nervous system and cardiac side effects and has a short action time, so clinicians in large hospitals at home and abroad rarely use chlorpheniramine. However, due to its low price, chlorpheniramine is still one of the anti-allergic drugs frequently used in rural areas or primary medical institutions in China. The main adverse reactions of chlorpheniramine are obvious drowsiness, palpitations, etc., especially the side effects on the heart and kidneys, which have aroused people’s vigilance. Children and elderly patients should use chlorpheniramine with caution.
[Drug Overview]
Drug name: Chlorpheniramine
English name: Chlorphenamine
Synonyms of chlorpheniramine: chlorpheniramine; chlorpheniramine; chlorpheniramine; chlorpheniramine; chlorpheniramine; chlorpheniramine; /p>
Category: Anti-allergic drugs > Antihistamines
Dosage form: 1. Tablet: 4mg each. 2. Injection: 10mg/1ml, 20mg/2ml.
Organizational type:
[Indications]
Applicable to various allergic diseases, including allergic urticaria, facial dermatitis, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, contact dermatitis, insect bite dermatitis, angioedema, allergies Asthma and drug allergies, etc.
Used in combination with antipyretics and analgesics to treat colds.
[Mechanism of action]
Antihistamines are a class of drugs that can combat various pathological reactions caused by histamine. This class of drugs reversibly occupies histamine receptors and competitively blocks the binding of histamine to the receptors, thereby exhibiting antihistamine effects.
There are two types of histamine receptors, H1 and H2, which produce different effects when excited. Excitation of H1 receptors can cause bronchial and gastrointestinal smooth muscle contraction, vascular smooth muscle relaxation, atrial muscle contraction enhancement, atrioventricular conduction slowdown, etc. Excitation of H2 receptors can cause increased secretion of gastric acid from gastric parietal cells. Each of these two types of effects is antagonized by different drugs. H1 receptor antagonists replace histamine in the body and competitively antagonize its effects. It cannot inactivate histamine, nor does it inhibit its synthesis and release. Therefore, it is mainly used to relieve symptoms of allergic reactions, such as urticaria, angioedema, rhinitis, and conjunctivitis, and can also relieve itching caused by skin diseases; some traditional H1 receptor antagonists can antagonize acetylcholine, 5-HT, and adrenal glands. H1 receptor antagonists such as diphenhydramine, dimenhydrinate, and promethazine have antiemetic effects and can be used to treat nausea, vomiting, and diarrhea in Meniere’s disease and related diseases. symptom.
Some drugs also have anti-vertigo and sedative effects. Promethazine can be used for preoperative anesthesia and short-term treatment of insomnia due to its sedative effect. H1 receptor antagonists can enhance the effects of central depressant drugs such as ethanol, barbiturates, hypnotics, analgesics, anxiolytics, and tranquilizers. Monoamine oxidase inhibitors may potentiate its anticholinergic effects. The drug can also synergize with the effects of atropine and tricyclic antidepressants. It can mask the ototoxicity of aminoglycosides, etc., causing false positives in skin tests and premature discontinuation of drugs. Before using antihistamines, you should fully understand their incompatibility. Combined use with sedatives, hypnotics, tranquilizers or ethanol drinks can enhance the central inhibitory effect. Delays the intrahepatic metabolism of phenytoin sodium and increases its plasma concentration.
[Pharmacokinetics]
Urine contained 13.2% of the original substance, 5.8% of N-desmethylchlorpheniramine, chlorpheniramine N-oxide, and two unidentified metabolites. Most of the drugs taken are excreted as polar metabolites. Chlorpheniramine is metabolized by the liver and excreted in urine, stool, and sweat. Breastfeeding women may also excrete part of it through breast milk. Medications taken during pregnancy can affect the fetus through cord blood.
[Adverse reactions]
The main adverse reactions of this type of drug include central nervous system depression, manifested as fatigue, dizziness, drowsiness, somnolence, etc. This drug also causes extrapyramidal reactions, gastrointestinal dysfunction, photosensitive dermatitis, and blood phase disorders. Note: This drug should not be used on premature infants and newborns. Infants of this age are sensitive to its anticholinergic effects; older childrenIt is also very sensitive to use, sedation and hypotension. Due to the drowsiness side effects of antihistamines, patients should not drive vehicles, operate machinery, or drink alcohol after taking the drugs. Due to their atropine-like effects, H1 receptor antagonists should be used with caution in patients with angle-closure glaucoma, urinary retention, prostatic hypertrophy, and pyloduodenal obstruction. Patients with epilepsy, severe cardiovascular or severe liver disease, patients with asthma who are taking phenothiazines, should be aware of additional side effects when taking antihistamines. Taking it during pregnancy may cause birth defects, but there is insufficient evidence. The usual dosage for adults is 4 mg each time, 2-3 times/d; children aged 2-5 years old can be injected subcutaneously, intramuscularly, or diluted and injected slowly intravenously. The dose is 10-20 mg/time, and the total dose within 24 hours should not exceed 40 mg.
There may be slight dry mouth, dizziness, nausea, drowsiness, palpitations or skin ecchymosis, and bleeding tendency, but these are rare.
Do not take while drinking
[Precautions when using medication]
1. It is prohibited for patients with epilepsy, infants and nursing mothers, and chlorpheniramine is prohibited or used with caution for drivers, pilots, high-altitude workers, dangerous machine operators, precision workers and students.
2. If you experience serious adverse reactions when using chlorpheniramine, or overdose, please seek medical attention immediately.
3. Use chlorpheniramine with caution in newborns, pregnant women, lactating women, prostatic hyperplasia, bladder neck obstruction, pyloduodenal obstruction, hyperthyroidism, and hypertension.
4. This product can easily cause central nervous system excitement and induce epilepsy, so patients with epilepsy should avoid using chlorpheniramine.
5. Chlorpheniramine is prohibited for those who are allergic to this product.
6. It is forbidden to take chlorpheniramine when the properties of the drug change.
7. The elderly who are more sensitive should reduce the dosage appropriately. Use of this product in elderly patients can easily cause dizziness, headache, hypotension, etc., so chlorpheniramine should be used with caution.
8. Patients with heart disease should use it with caution. Patients with pyloric obstruction, prostatic hypertrophy, bladder obstruction, glaucoma, hyperthyroidism and hypertension should use chlorpheniramine with caution.
9. Children should use chlorpheniramine under the guidance of a doctor and under the supervision of their parents. Please keep this medicine out of the reach of children. [2]
[Treatment Points]
The key points in the treatment of chlorpheniramine poisoning are symptomatic treatment, that is, treatment of the main symptoms of the external manifestations of the disease, or temporary treatment. Traditional Chinese medicine does not advocate symptomatic treatment, because sometimes symptoms do not reflect the essence of the disease, and uncertainty may lead to mistreatment. However, when the diagnosis is unclear or the signs are urgent, the symptoms should be treated, and symptomatic treatment is necessary. Modern medicine believes that the purpose of symptomatic treatment is to relieve the patient’s pain, control the development of the disease, buy time and create conditions for curing the patient. In some serious and critical illnesses, such as shock, convulsions, heart failure, high fever, and severe pain, symptomatic treatment may be more urgent than treating the cause. [3]
[1]^Shen Xinfu et al. ed. Dictionary of Practical Chemistry for Middle School Teachers. Beijing: Beijing Science and Technology Press. 2002. No. 298
[2]^Good Doctor Online: The functions and precautions of chlorpheniramine, 2011-11-24
[3]^Editor-in-Chief Zhang Yu. Acute Poisoning[M]. Xi’an: Fourth Military Medical University Press, 2008: 209
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