Usage
Dextromethorphan Hydrobromide + Phenylephrine is prescribed for the temporary relief of cough, nasal congestion, and sinus pain/pressure caused by the common cold, flu, or other respiratory illnesses like hay fever and bronchitis. It is not effective against coughs with excessive mucus.
It combines drugs from two pharmacological classifications:
- Dextromethorphan Hydrobromide: Antitussive (Cough suppressant).
- Phenylephrine: Decongestant (Sympathomimetic amine).
Mechanism of Action: Dextromethorphan works centrally in the brain to suppress the cough reflex. Phenylephrine constricts blood vessels in the nasal passages, reducing swelling and congestion.
Alternate Names
This combination doesn’t have a specific international non-proprietary name (INN). It’s recognized by its component drugs. Several brand names exist, which can vary regionally. Examples include:
- Vicks DayQuil Cold & Flu
- Dimetapp Children’s Cold & Cough
- Tylenol Cold Multi-Symptom Severe Daytime
- Robitussin DM
How It Works
Pharmacodynamics:
- Dextromethorphan: Acts centrally on the cough center in the medulla oblongata to suppress the cough reflex. It’s a non-opioid antitussive and doesn’t exhibit analgesic or addictive properties.
- Phenylephrine: Stimulates alpha-adrenergic receptors in the nasal mucosa, causing vasoconstriction. This reduces blood flow, leading to decreased swelling and congestion.
Pharmacokinetics:
- Dextromethorphan: Well-absorbed orally. Extensively metabolized in the liver, primarily by CYP2D6. Excreted mainly in urine as metabolites.
- Phenylephrine: Poorly absorbed orally. Metabolized by monoamine oxidase (MAO) in the gastrointestinal tract and liver. Eliminated in urine.
Mode of Action:
- Dextromethorphan: Binds to sigma-1 receptors and, to a lesser extent, NMDA receptors in the brain. Its precise mechanism for cough suppression isn’t fully understood.
- Phenylephrine: Acts as an alpha-1 adrenergic receptor agonist, causing vasoconstriction.
Elimination Pathways: Both drugs and their metabolites are primarily eliminated through renal excretion.
Dosage
Standard Dosage
Adults:
Liquid formulations: Typically, 10-30 mL every 4-6 hours, not exceeding the maximum daily dose specified for each component drug.
Other formulations: Dosage varies depending on the specific product. Always follow product labeling and consult a physician.
Children:
Dosage is weight- or age-dependent and must be carefully determined based on specific product formulations. Generally:
- 2 to under 6 years: 1.25-2.5 mL every 4-6 hours (consult product labeling).
- 6 to under 12 years: 2.5 - 10 mL every 4-6 hours (consult product labeling).
- 12 years and older: Refer to adult dosing.
Caution: Cough and cold products are not recommended for children under 4 years old unless specifically directed by a doctor.
Special Cases:
- Elderly Patients: Start with lower doses due to potential age-related decline in organ function.
- Patients with Renal Impairment: Dose adjustment may be needed.
- Patients with Hepatic Dysfunction: Dose reduction may be necessary.
- Patients with Comorbid Conditions: Use with caution in patients with hypertension, diabetes, heart disease, hyperthyroidism, glaucoma, or prostatic hypertrophy.
Clinical Use Cases
Dextromethorphan + Phenylephrine isn’t typically indicated for use in clinical settings like intubation, surgical procedures, mechanical ventilation, or the ICU.
Dosage Adjustments
Adjustments may be necessary based on patient-specific factors like renal/hepatic impairment, metabolic disorders, or genetic polymorphisms. Always consult with a specialist or pharmacist.
Side Effects
Common Side Effects:
Drowsiness, dizziness, nausea, vomiting, dry mouth, nervousness, insomnia, headache.
Rare but Serious Side Effects:
Allergic reactions (hives, difficulty breathing, swelling), hallucinations, confusion, seizures, rapid or irregular heartbeat, severe dizziness, anxiety, difficulty urinating.
Long-Term Effects:
Chronic use of phenylephrine can lead to rebound congestion.
Adverse Drug Reactions (ADR):
Any severe or unusual reaction requires immediate medical attention.
Contraindications
- Hypersensitivity to dextromethorphan or phenylephrine.
- Concurrent or recent (within 14 days) use of MAO inhibitors.
- Severe hypertension or coronary artery disease.
- Narrow-angle glaucoma or urinary retention.
Drug Interactions
- MAO Inhibitors: Can cause serious interactions, including hypertensive crisis.
- Other CNS Depressants: May potentiate drowsiness.
- Tricyclic Antidepressants: Can increase the risk of cardiovascular side effects.
- Beta-blockers: May interact with phenylephrine, leading to hypertension.
- Alcohol: May increase the risk of side effects.
Pregnancy and Breastfeeding
- Pregnancy: Use with caution. Consult a physician to assess the risks and benefits. No definitive studies confirm absolute safety.
- Breastfeeding: Dextromethorphan is considered relatively safe. Phenylephrine may decrease milk supply. Consult a physician before use.
Drug Profile Summary
- Mechanism of Action: Dextromethorphan: Central cough suppressant. Phenylephrine: Alpha-1 adrenergic agonist, decongestant.
- Side Effects: Drowsiness, dizziness, nausea, dry mouth, nervousness, insomnia. Serious: Allergic reactions, hallucinations, seizures, cardiac arrhythmias.
- Contraindications: Hypersensitivity, MAOI use, severe hypertension, narrow-angle glaucoma.
- Drug Interactions: MAOIs, CNS depressants, tricyclic antidepressants, beta-blockers.
- Pregnancy & Breastfeeding: Use with caution; consult a physician.
- Dosage: Varies by formulation and age. Refer to product labeling or consult a physician.
- Monitoring Parameters: Blood pressure, heart rate, respiratory rate, mental status.
Popular Combinations
Often combined with other cold and flu medications, including antihistamines (e.g., chlorpheniramine, diphenhydramine) and analgesics/antipyretics (e.g., acetaminophen).
Precautions
Screen for pre-existing conditions like hypertension, diabetes, and glaucoma. Caution in pregnant/breastfeeding women, children, and the elderly. Avoid alcohol and operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dextromethorphan Hydrobromide + Phenylephrine?
A: Dosage varies depending on age, the specific product formulation (liquid, tablet, etc.), and the concentrations of dextromethorphan and phenylephrine. Always refer to the product labeling for specific instructions. Consult a physician for dosage guidance in children, the elderly, or those with underlying health conditions.
Q2: Can this combination be used in patients with high blood pressure?
A: Phenylephrine can raise blood pressure. Use with caution in patients with hypertension, and monitor blood pressure closely. In severe hypertension, it’s contraindicated.
Q3: Can pregnant or breastfeeding women take this medicine?
A: Consult a physician before using this medication during pregnancy or while breastfeeding. While generally considered safe, individual risk-benefit assessments are crucial.
Q4: What are the signs of an allergic reaction to this drug?
A: Hives, itching, skin rash, swelling (especially of the face, lips, tongue, or throat), difficulty breathing, dizziness, lightheadedness. Seek immediate medical attention if these occur.
Q5: Can I take this with other cold and flu medications?
A: Caution is advised. Many OTC cold and flu products contain similar ingredients. Combining them could lead to an overdose of certain components (e.g., acetaminophen, dextromethorphan, phenylephrine). Always check labels carefully and consult a physician or pharmacist before combining medications.
Q6: Does this medication cause drowsiness?
A: Yes, drowsiness is a common side effect, especially with higher doses or when combined with other CNS depressants. Avoid operating heavy machinery or driving after taking this medication.
Q7: 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 your regular dosing schedule. Do not double the dose.
Q8: Can I use this product if I have glaucoma?
A: Phenylephrine can exacerbate glaucoma. It’s contraindicated in narrow-angle glaucoma and should be used cautiously in other forms of glaucoma under close ophthalmologic supervision.
Q9: Are there any dietary restrictions while taking this medication?
A: Alcohol should be avoided as it can worsen potential side effects like drowsiness and dizziness. No specific food interactions are known.
