Anti-Cough Drugs aka. Anti-Antitussives Drugs

A comprehensive table summarizes the cough management drugs, including dosages and indications for different age groups.

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Introduction

Cough is a common symptom of various respiratory conditions, including upper respiratory tract infections, bronchitis, asthma, chronic obstructive pulmonary disease (COPD), and even gastroesophageal reflux disease (GERD). It is generally classified as:

1. Dry cough (non-productive): Does not produce mucus and is often irritating or tickling.
2. Wet cough (productive): Accompanied by mucus or phlegm production.

The treatment approach involves addressing the underlying cause while using anti-cough medications to provide symptomatic relief.

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Types of Anti-Cough Medications

1. Cough Suppressants (Antitussives)
   • These medications act on the brain's cough center, located in the medulla oblongata, to suppress the cough reflex.
   • Indications: Best suited for dry, irritating coughs where reducing the frequency of coughing can improve patient comfort.

   Common Cough Suppressants

   • Dextromethorphan
     • Mechanism: Acts on the sigma-1 receptor and NMDA receptors in the brain to elevate the cough threshold.
     • Dosage:
       • Adults and children ≥12 years: 10-20 mg every 4 hours, or 30 mg every 6-8 hours. Do not exceed 120 mg per day.
       • Children 6-12 years: 5-10 mg every 4 hours, or 15 mg every 6-8 hours. Do not exceed 60 mg per day.
       • Children 4-6 years: 2.5-5 mg every 4 hours, or 7.5 mg every 6-8 hours. Do not exceed 30 mg per day.
     • Clinical Considerations: May cause dizziness, nausea, or gastrointestinal disturbances. Caution in patients taking monoamine oxidase inhibitors (MAOIs) due to the risk of serotonin syndrome.
   • Benzonatate
     • Mechanism: A non-opioid antitussive that anesthetizes stretch receptors in the respiratory passages, lungs, and pleura, reducing the cough reflex.
     • Dosage:
       • Adults and children ≥10 years: 100-200 mg three times daily as needed.
     • Clinical Considerations: Capsules must be swallowed whole to avoid oral anesthesia and choking risk.
2. Expectorants
   • Used to treat wet coughs by helping thin and loosen mucus in the airways, facilitating its clearance.
   • Indications: Useful for conditions like bronchitis and other lower respiratory tract infections where mucus production is prominent.

   Common Expectorants

   • Guaifenesin
     • Mechanism: Increases the hydration of respiratory tract mucus, making it easier to cough up.
     • Dosage:
       • Adults and children ≥12 years: 200-400 mg every 4 hours. Maximum daily dose is 2400 mg.
       • Children 6-11 years: 100-200 mg every 4 hours. Maximum daily dose is 1200 mg.
     • Clinical Considerations: Well-tolerated, but may cause nausea, vomiting, or dizziness.
   • Acetylcysteine
     • Mechanism: Breaks the disulfide bonds in mucoproteins, decreasing mucus viscosity.
     • Dosage:
       • Inhalation: 3-5 mL of a 20% solution or 6-10 mL of a 10% solution, three to four times daily.
       • Oral: 200 mg three times daily.
     • Clinical Considerations: Has a strong sulfur-like odor, which some patients may find unpleasant.
3. Mucolytics: AmbroxolAmbroxol is a mucolytic agent that helps reduce the viscosity of mucus, aiding in its clearance from the respiratory tract. It not only enhances mucus expectoration but also has other benefits that can aid in managing cough.
   • Mechanism of Action:
     • Ambroxol works by increasing the serous component of bronchial secretions, making the mucus less viscous and easier to expectorate.
     • It also stimulates the ciliary activity in the respiratory tract, facilitating the movement of mucus toward the throat.
     • Ambroxol has additional properties, including local anesthetic effects, which can soothe an irritated throat and reduce coughing. This effect is due to the inhibition of neuronal sodium channels, which can help reduce pain or discomfort associated with cough.
   • Indications:
     • Commonly used in acute and chronic respiratory conditions, such as bronchitis, COPD, and asthma, where mucus production is increased.
     • Also utilized in patients with cystic fibrosis as an adjunctive therapy.
   • Dosage:
     • Adults and children ≥12 years: 30 mg taken orally, three times daily. The dosage can be increased to 60 mg twice daily for severe cases.
     • Children 6-12 years: 15 mg taken orally, two to three times daily.
     • Children 2-6 years: 7.5 mg taken orally, two to three times daily.
     • For inhalation therapy: 15 mg/2 mL, used with a nebulizer once or twice daily.
   • Clinical Considerations:
     • Ambroxol is generally well-tolerated, with potential side effects including gastrointestinal disturbances, headache, or rash.
     • Has shown some efficacy in reducing sore throat symptoms due to its local anesthetic properties.
     • Should be used with caution in patients with peptic ulcers due to potential gastrointestinal irritation.
4. AntihistaminesAntihistamines can be used to relieve coughs associated with allergic reactions or post-nasal drip.
   • Diphenhydramine
     • Mechanism: H1 receptor antagonist that reduces the effects of histamine on the respiratory tract, helping reduce post-nasal drip-induced cough.
     • Dosage:
       • Adults and children ≥12 years: 25-50 mg every 4-6 hours. Maximum daily dose is 300 mg.
       • Children 6-11 years: 12.5-25 mg every 4-6 hours. Maximum daily dose is 150 mg.
     • Clinical Considerations: Can cause sedation, so it should be used cautiously, especially in elderly patients.
5. Opioid-Based Cough Suppressants
   • Codeine
     • Mechanism: Binds to opioid receptors in the brain, reducing the activity of the cough center.
     • Indications: Severe coughs that are not relieved by non-opioid treatments.
     • Dosage:
       • Adults: 10-20 mg every 4-6 hours. Maximum daily dose is 120 mg.
       • Children 12-18 years: 5-10 mg every 4-6 hours. Maximum daily dose is 60 mg.
     • Clinical Considerations: Risk of respiratory depression, constipation, and potential for abuse. Contraindicated in children under 12 and patients with severe respiratory conditions.

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Combining Anti-Cough Medications

For some patients, combining an expectorant with a cough suppressant may be appropriate. For instance:

• In cases of nighttime cough where thick mucus is present, an expectorant can be used during the day to loosen mucus, while a cough suppressant is taken at night for relief.

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Cautions and Clinical Considerations

• Persistent Symptoms: If cough persists for more than 3 weeks or is associated with alarming symptoms (e.g., weight loss, hemoptysis, fever, night sweats), further evaluation is needed to rule out conditions like tuberculosis or lung cancer.
• Underlying Conditions: Always consider the underlying cause of the cough. In cases such as heart failure or GERD, treating the underlying condition will be more effective than merely suppressing the cough.
• Drug Interactions: Monitor for potential interactions, especially with codeine, which may have additive effects with other central nervous system depressants.

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Summary

Managing cough effectively involves selecting the appropriate anti-cough medication based on the type of cough and underlying cause. Ambroxol stands out as a versatile option due to its mucolytic, expectorant, and local anesthetic properties, making it beneficial for patients with conditions characterized by increased mucus production. It is important for clinicians to individualize treatment plans, considering patient-specific factors, to ensure optimal outcomes.