An expectorant is a commonly used drug for respiratory diseases, and it is also a class of drugs that young doctors in the respiratory department must understand and master.
This article first introduces the general basic knowledge of commonly used clinical expectorants, including pharmacological effects, usage and dosage, etc., and finally analyzes and explains the rationality of expectorants through several cases of irrational drug use. It is hoped that the clinical understanding of expectorants can be improved and rational use can be promoted!
Expectants can be divided into three categories according to their mechanism of action
1. Nausea expectorants and irritating expectorants: Such as ammonium chloride, potassium iodide, guaifenesin, etc., can irritate gastric mucosa after oral administration , causes mild nausea, reflexively promotes increased secretion of airway glands, dilutes sputum and makes it easier to cough up.
2. Sputum dissolving agents: Such as ambroxol, bromhexine, acetylcysteine and other viscous components that can decompose sputum, such as mucopolysaccharides and mucin, liquefying phlegm, reducing its viscosity and making it easier to cough up.
3. Mucus thinners: Such as oxycisteine, standard myrtle oil, eucalyptus, lime and pinene, etc. Promote the secretion of low-viscosity secretions, so that the rheological properties of respiratory secretions return to normal, and the sputum becomes thinner and easier to cough up.
Let’s take a detailed look at the clinical applications of various drugs.
One. Nausea and irritating expectorants
1. Ammonium Chloride
It is often used in combination with other cough and expectorant drugs, such as compound codeine phosphate solution. At the same time, it can correct metabolic alkalosis, acidify urine, and promote the excretion of alkaline urine.
Usage and Dosage: Expectorant: Oral, 0.3 ~ 0.6 g per adult, 3 times a day, dissolve in water, and take after meals. Treatment of metabolic alkalosis or acidified urine: intravenous infusion, 2 to 20 g per day, no more than 5 g per hour.
Precautions: Swallowing the tablet or overdosing can cause nausea, vomiting, stomach pain and other irritating symptoms; this product can increase blood ammonia concentration, and those with liver insufficiency can induce hepatic encephalopathy, Therefore, it is contraindicated in patients with liver and renal insufficiency; excessive use or long-term use can easily lead to hyperchloremic acidosis, and patients with metabolic acidemia are contraindicated.
2. Potassium Iodide
It is now commonly used to treat thyroid diseases, and is less used for expectoration.
Usage and dosage and precautions are omitted.
3. Guaifenesin
Usage and Dosage: Take orally, after meals. Tablets (0.2 g per tablet): 0.2 g each time, 3 to 4 times a day. Syrup (2% 120 mL): 10~20 mL each time, 3 times a day. Granules (10 g: 0.8 g/bag): 1/4 bag for adults, 4 times a day.
The drug is also combined with other antitussive and antiasthmatic drugs for respiratory diseases, such as compound potassium guaiacol sulfonate oral solution, dextromethorphan guaifenesin Syrup etc.
Precautions: Contraindicated in pulmonary hemorrhage, nephritis, or acute gastroenteritis; contraindicated in women within 3 months of pregnancy.
Irritant expectorants such as eucalyptus oil, tincture of benzoin, etc. are basically not used because of their inconvenience.
II. Mucolytics
1. Bromhexine
This product not only has the effect of dissolving phlegm, but also promotes the movement of mucociliary in the respiratory tract and has a disgusting expectorant effect. The effect starts about 1 hour after taking it, the effect reaches a peak in 4~5 hours, and the effect lasts for 6~8 hours.
Usage and Dosage: Adult: Oral: 8~16 mg once, 2 times a day. Intramuscular injection: 4-8 mg once, 2 times a day. Intravenous infusion: 4-8 mg a day, add 500 mL of 5% dextrose and sodium chloride solution. Inhalation by atomization: 2 mL at a time, 2-3 times a day.
Precautions: This product is irritating to the gastrointestinal mucosa and should be used with caution in patients with gastritis or gastric ulcer; patients with hepatic insufficiency should be used under the guidance of a physician.
2. Ambroxol
This product is a metabolite of bromhexine in the body. Its expectorant effect is significantly higher than that of bromhexine, and the toxicity is small and the tolerance is good. It takes effect 1 hour after nebulization or oral administration, and the effect lasts for 3 to 6 hours. The high dose of this product (250-500 mg each time, twice a day) has the effect of reducing plasma uric acid concentration and promoting uric acid excretion, and can be used for the treatment of gout.
Usage and Dosage: Oral: 30 mg for adults, 3 times a day. For long-term use (after 14 days) the dose can be halved. Intravenous, intramuscular, and subcutaneous: 15 mg twice a day for adults. It can also be added to normal saline or glucose solution for intravenous infusion.
Cautions: Use with caution within 3 months of pregnancy; injection should not be mixed with other solutions with a pH greater than 6.3.
3. Acetylcysteine
The injection form of this product can be used for the detoxification of acetaminophen poisoning and the treatment of hemorrhagic cystitis caused by cyclophosphamide. There are special aerosol inhalation dosage forms (3 mL: 0.3 g) and oral dosage forms (tablets, capsules, granules, effervescent tablets) for breaking down sticky phlegm
Usage and dosage: Nebulized inhalation: 3 mL each time, 1~2 times each time, for 5~10 days. Dosage frequency can be adjusted according to clinical efficacy. Oral: Capsules: 0.2 g each time, 2~3 times a day; Tablets, effervescent tablets: 0.6 g once, 1~2 times a day or as directed by a doctor; Granules: 0.2 g once, 3 times a day.
Precautions: It can cause choking and bronchospasm, and is contraindicated in patients with bronchial asthma.
Three. Mucus Thinner
1. Oxycine
This product is an oral dosage form, which has a rapid onset of action, and the obvious effect can be seen 4 hours after taking it. It can also be used for non-suppurative otitis media in children and has the effect of preventing deafness.
Usage and dosage: Oral, 0.25~0.5 g each time for adults, 3 times a day.
Precautions: Use with caution in patients with a history of peptic ulcer; elderly patients with chronic liver disease should reduce the dose.
2. Standard Myrtle
This product is a fat-soluble volatile oil. It is a capsule (300 mg/capsule for adults, 120 mg/capsule for children), after oral administration, it is absorbed through the small intestine, and then excreted through the respiratory tract. In addition to decomposing sticky phlegm, it also has a mild anti-inflammatory effect, which can reduce the swelling of the bronchial mucosa and dilate the bronchi, thereby reducing airway obstruction. It is also used after bronchography to promote the excretion of contrast agents.
Usage and Dosage: Take orally, take the whole capsule with more cold water 30 minutes before meals. Adults: Acute patients: 1 capsule each time, 3-4 times a day; chronic patients: 1 capsule each time, 2 times a day.
Notes: This product is in capsule form and should be swallowed whole, the capsule should not be damaged, and it is forbidden to take it with hot water; it has been proven safe to take during pregnancy, because the drug can be secreted into breast milk , should be used with caution during breastfeeding.
3. Eucalyptus, lemon and pinene (dosage and precautions are the same as standard myrtle oil)
How to use expectorants wisely
How to use expectorants rationally in clinical practice involves three factors: disease, drug and human.
Diseases mainly refer to whether there are indications or not. Expectorants are mainly used for patients with thick phlegm that is difficult to expectorate, which is relatively easy to grasp;
Drugs refer to whether the dosage of the drug is correct, whether it violates the contraindication, whether there is drug interaction, etc.;
Human factors involve physiological characteristics (age, gender, pregnancy, breastfeeding, etc.), occupation, comorbidities, organ functions, etc.
We discuss how to rationally use expectorants through the following unreasonable cases.
Case 1: Prescribe bromhexine intravenously and oral ambroxol tablets at the same time
Analysis: Ambroxol is the active metabolite of bromhexine, both of which have the same pharmacological mechanism and belong to repeated medication. If the patient needs long-term medication, the sequential administration method of intravenous first and then oral can be adopted.
Case 2: Prescribing standard myrtle oil and eucalyptus pinene at the same time for the patient
Analysis: The two drugs are both mucus thinners, and the simultaneous use is a repeated drug. It is recommended to use one.
The above two cases belong to the situation of repeated use of drugs. If one drug cannot effectively dilute the sputum, if it is considered to be used in combination, it is recommended to choose the combination of drugs with different pharmacological effects. Whether use will increase the risk of adverse drug reactions and patient compliance. For example, although ammonium chloride-containing drugs and bromhexine have different pharmacological mechanisms, combined use may increase gastrointestinal irritation and increase the burden on the liver. Here, it is necessary to comprehensively evaluate the patient’s tolerance and organ function.
Case 3: Prescribe compound codeine phosphate solution for cough and expectoration patients with active liver disease
Analysis: The components of compound codeine phosphate solution include ephedrine hydrochloride, codeine phosphate, chlorpheniramine maleate and ammonium chloride, and ammonium chloride is contraindicated in patients with hepatic insufficiency Otherwise, ammonium poisoning will occur due to the inability of the liver to convert ammonium ions into urea.
Case 4: Prescribing inhaled acetylcysteine for bronchial asthma patients
Analysis: Acetylcysteine solution can cause bronchospasm and is contraindicated in patients with bronchial asthma.
The above two cases both violated the contraindications of the drug, and hope to attract the attention of doctors. At the same time, expectorants on the market are mostly combined with other antitussive and antiasthmatic drugs to form compound preparations. Clinicians need to carefully understand each of its components, indications and contraindications, and apply them individually on the premise of ensuring safety.
Case 5: Prescribing both acetylcysteine and cephalosporin in patients with respiratory tract infections
Analysis: Acetylcysteine can reduce the activity of penicillins and cephalosporins, so simultaneous use should be avoided, and interval dosing can be considered when necessary.
Ambroxol hydrochloride concomitantly with antibiotics (amoxicillin, cefuroxime, erythromycin) can lead to increased concentrations of antibiotics in the lung tissue, possibly enhancing anti-infective efficacy. Therefore, the patient suggested that it is more appropriate to switch to ambroxol.
Summary
In short, expectorants should be used individually on the basis of comprehensive evaluation of three factors: disease, drug, and human. For example, acetylcysteine can be used for patients with hepatic insufficiency, and standard myrtle oil can be used for patients after bronchography to promote contrast medium excretion.
The most important point is that mucolytics and mucus thinners should not be used in combination with strong antitussives, in order to prevent the increased sputum that cannot be coughed up and cause severe symptoms.heavy consequences.
References:
[1] Chen Xinqian, Jin Youyu, Tang Guang. “New Pharmacology” 18th Edition, 505-509.
[2] Medication Instructions.