Usage
This combination medication is primarily prescribed for the symptomatic relief of coughs and nasal congestion associated with the common cold, flu, allergies, and other upper respiratory tract infections. It is also used to relieve throat irritation.
Its pharmacological classifications include:
- Antitussive (Cough suppressant, specifically Diphenhydramine)
- Expectorant (Ammonium Chloride)
- Mucolytic (Citric Acid and Sodium Citrate, if present in the formulation)
- Demulcent/Soothing agent (Menthol)
- Antihistamine (Diphenhydramine)
The mechanism of action involves multiple components:
- Ammonium chloride increases respiratory tract secretions, thinning mucus and making coughs more productive.
- Citric acid stimulates throat mucous membranes, increasing blood flow and soothing soreness.
- Diphenhydramine, an antihistamine, blocks the effects of histamine, reducing allergy symptoms like runny nose, sneezing, and coughing.
- Menthol provides a cooling sensation and mild local anesthetic effect, relieving throat irritation and cough.
Alternate Names
There is no single international non-proprietary name (INN) for this combination product. It is often referred to by the names of its constituent ingredients. Brand names vary depending on the manufacturer and region. Some examples include Benylin Original, Coflax Cough Syrup, and others.
How It Works
Pharmacodynamics:
- Ammonium Chloride: Acts as an expectorant by stimulating secretions in the respiratory tract. It also increases the pH of bronchial secretions which thins mucus. This facilitates easier expectoration.
- Citric Acid: Acts as a mucolytic by breaking down thick mucus. Additionally, it can also be used as mild local anesthetic, increasing blood flow and soothing soreness.
- Diphenhydramine: A first-generation antihistamine that competitively antagonizes the H1 histamine receptor. This action reduces the effects of histamine, leading to decreased allergy symptoms like sneezing, runny nose, watery eyes, and cough due to histamine release. It also has antitussive (cough suppressant) and sedative properties through its central nervous system effects.
- Menthol: Stimulates cold receptors in the mucous membranes, creating a cooling sensation and relieving irritation. It also acts as a weak local anesthetic and mild cough suppressant.
Pharmacokinetics:
- Absorption: Orally administered, this combination is absorbed through the gastrointestinal tract.
- Metabolism: Diphenhydramine is extensively metabolized in the liver, primarily via CYP2D6. The other ingredients are also metabolized, although the details may vary.
- Elimination: The metabolites are primarily excreted in the urine.
Dosage
Dosage guidelines vary by region, brand, and specific product formulation. Always consult the local product labeling and/or prescribing information. The following represents general guidelines and some examples from various sources, and should not be used as the sole basis for dosing decisions.
Standard Dosage
Adults:
- Typical dosage is 5-10 mL every 4-6 hours, not exceeding 6 doses in 24 hours.
Children:
- The combination is generally not recommended for children under 2 years of age.
- Dosing for older children varies depending on age and formulation. Consult specific product information or a pediatrician. Examples include 2.5-5 mL every 4 hours for children 6-12 years.
Special Cases:
- Elderly Patients: Start with the lower end of the adult dosage range. Close monitoring for side effects is recommended.
- Patients with Renal Impairment: Dose adjustment may be necessary. Monitor renal function.
- Patients with Hepatic Dysfunction: Caution and dose adjustment are advised due to diphenhydramine’s hepatic metabolism. Monitor liver function.
- Patients with Comorbid Conditions: Exercise caution in patients with asthma, COPD, glaucoma, prostate enlargement, urinary retention, cardiovascular disease, or hyperthyroidism.
Clinical Use Cases
This specific combination is generally not indicated for use in intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations.
Dosage Adjustments
Dosage adjustments should be individualized based on patient response, renal and hepatic function, comorbid conditions, and concomitant medications. Always refer to product labeling and/or consult a pharmacist or physician.
Side Effects
Common Side Effects
- Drowsiness
- Dry mouth, nose, and throat
- Dizziness
- Headache
- Nausea and vomiting (especially with higher doses of ammonium chloride)
- Blurred vision
- Constipation
- Urinary hesitancy or retention
Rare but Serious Side Effects
- Allergic reactions (rash, urticaria, angioedema)
- Paradoxical excitation (especially in children)
- Seizures
- Hallucinations
- Cardiac arrhythmias
Long-Term Effects
Chronic use is generally not recommended. Potential long-term effects are not well established for this combination.
Contraindications
- Hypersensitivity to any of the ingredients
- Narrow-angle glaucoma
- Severe liver or kidney disease
- Severe respiratory diseases such as asthma or COPD (unless under direct medical supervision)
- MAOI therapy (or within 14 days of stopping MAOIs)
- Newborns and premature infants
Drug Interactions
- Alcohol: Increases sedative effects. Avoid concomitant use.
- CNS depressants (e.g., sedatives, hypnotics, opioids, anxiolytics, antipsychotics): Enhanced sedation. Use with caution.
- Anticholinergics (e.g., tricyclic antidepressants, some antipsychotics): Additive anticholinergic effects (dry mouth, blurred vision, constipation, urinary retention).
- Sympathomimetics (e.g., ephedrine, pseudoephedrine): May have additive or antagonistic effects. Monitor closely.
- MAOIs: Risk of serotonin syndrome. Contraindicated.
Pregnancy and Breastfeeding
- Pregnancy: While some components are classified as Pregnancy Category A in certain regions (meaning no demonstrated risk in controlled human studies), the combination as a whole has not been extensively studied in pregnancy. Use only if the potential benefit outweighs the potential risk to the fetus.
- Breastfeeding: Diphenhydramine is excreted in breast milk. The effects of the combination on infants are not well studied. Consult a physician before use during breastfeeding.
Drug Profile Summary
- Mechanism of Action: See “How It Works” section above.
- Side Effects: See “Side Effects” section above.
- Contraindications: See “Contraindications” section above.
- Drug Interactions: See “Drug Interactions” section above.
- Pregnancy & Breastfeeding: See “Pregnancy and Breastfeeding” section above.
- Dosage: See “Dosage” section above.
- Monitoring Parameters: Respiratory status, mental status, and adverse effects. Monitor liver and kidney function in patients with pre-existing dysfunction.
Popular Combinations
This combination is generally not combined with other drugs.
Precautions
- Pre-existing conditions: Assess patients for conditions listed in the “Contraindications” section.
- Pregnant/breastfeeding women: Use with caution. See “Pregnancy and Breastfeeding.”
- Children and elderly: Age-appropriate formulations and dosing are essential.
- Lifestyle: Avoid alcohol and operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Ammonium Chloride + Citric Acid + Diphenhydramine + Menthol?
A: See “Dosage” section above. Dosing varies by age, specific product formulation, and clinical context. Always consult the product labeling.
Q2: Can this combination be used in children under 2 years of age?
A: Generally not recommended for children under 2 years. Consult a pediatrician.
Q3: What are the most common side effects?
A: Drowsiness, dry mouth, dizziness, and headache.
Q4: Are there any serious side effects to be aware of?
A: Yes, although rare, serious side effects can include allergic reactions, paradoxical excitation, seizures, and hallucinations.
Q5: Can I take this medication while pregnant or breastfeeding?
A: Consult a physician before use during pregnancy or while breastfeeding. The risks and benefits must be carefully considered.
Q6: What other medications should I avoid while taking this combination?
A: Avoid alcohol, CNS depressants, anticholinergics, and MAOIs. Other interactions are possible. Consult a physician or pharmacist.
Q7: Can I drive after taking this medication?
A: Caution is advised as drowsiness may occur. Avoid driving or operating machinery if you experience drowsiness.
Q8: What should I do if I miss a dose?
A: Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not double the dose.
Q9: What is the difference between expectorants and mucolytics?
A: Expectorants increase respiratory tract secretions, while mucolytics break down the existing mucus, both aiding in clearing the airways.
Q10: How long can I take this combination medication?
A: Consult a healthcare professional for the appropriate duration of treatment. Generally, it is used for short-term relief of symptoms. Prolonged use is not recommended without medical supervision.
