Usage
- This combination medication is prescribed for the short-term relief of symptoms associated with the common cold and allergies, such as cough, nasal congestion, runny nose, sneezing, itchy nose or throat, and watery eyes.
- Pharmacological Classification: This is a combination product containing a cough suppressant (dextromethorphan), a decongestant (phenylephrine), and an antihistamine (triprolidine).
- Mechanism of Action: Dextromethorphan suppresses the cough reflex by acting on the cough center in the brain. Phenylephrine constricts blood vessels in the nasal passages, reducing swelling and congestion. Triprolidine blocks the action of histamine, a substance that causes allergic symptoms.
Alternate Names
- No widely recognized alternate generic names exist.
- Brand Names: Histex-DM, Dr. Manzanilla DM, Triponel, and various other regional and international brand names.
How It Works
- Pharmacodynamics: Dextromethorphan acts centrally on the cough center in the medulla to suppress the cough reflex. Phenylephrine acts as an α1-adrenergic receptor agonist, causing vasoconstriction in the nasal mucosa. Triprolidine acts as an H1-receptor antagonist, blocking the effects of histamine.
- Pharmacokinetics: All three components are absorbed orally. Dextromethorphan is metabolized by the liver, primarily via CYP2D6, and excreted in the urine. Phenylephrine undergoes minimal first-pass metabolism and is excreted in the urine, both unchanged and as metabolites. Triprolidine is also metabolized by the liver and excreted in the urine.
- Mode of Action: Dextromethorphan’s antitussive effects are mediated through its action on sigma receptors and NMDA receptors in the brain. Phenylephrine binds to α1-adrenergic receptors, causing vasoconstriction, reducing nasal congestion. Triprolidine competitively inhibits the binding of histamine to H1 receptors, alleviating allergy symptoms.
- Elimination Pathways: Primarily hepatic metabolism and renal excretion for all three components.
Dosage
Standard Dosage
Adults: 1 teaspoonful (5 mL) every 4 hours, not exceeding 4 teaspoonfuls (20 mL) in 24 hours.
Children:
- 6 to under 12 years: ½ teaspoonful (2.5 mL) every 4 hours, not exceeding 2 teaspoonfuls (10 mL) in 24 hours.
- 2 to 6 years: Use with caution and only as advised by a physician.
- Under 2 years: Not recommended.
Special Cases:
- Elderly Patients: Start with a lower dose and monitor for adverse effects.
- Patients with Renal Impairment: Dose adjustment may be necessary.
- Patients with Hepatic Dysfunction: Dose reduction is usually required due to impaired metabolism.
- Patients with Comorbid Conditions: Careful monitoring and dose adjustments are essential, particularly for those with cardiovascular disease, hypertension, diabetes, hyperthyroidism, glaucoma, prostatic hypertrophy, or stenosing peptic ulcer.
Clinical Use Cases
This combination medication is not typically used in clinical settings like intubation, surgical procedures, mechanical ventilation, ICU, or emergency situations. Its primary use is for the symptomatic relief of common cold and allergy symptoms in an outpatient setting.
Dosage Adjustments
Dosage adjustments should be individualized based on patient factors such as age, weight, renal and hepatic function, and comorbidities.
Side Effects
Common Side Effects
Drowsiness, dizziness, dry mouth, nausea, constipation, blurred vision, restlessness, or difficulty sleeping.
Rare but Serious Side Effects
Allergic reactions (rash, hives, itching, swelling), hallucinations, rapid or irregular heartbeat, difficulty breathing, and seizures.
Long-Term Effects
Chronic use can lead to tolerance to the decongestant effect and rebound congestion.
Adverse Drug Reactions (ADR)
Severe allergic reactions (anaphylaxis), serotonin syndrome (with other serotonergic medications), and cardiac arrhythmias.
Contraindications
- Hypersensitivity to any of the components.
- Concurrent or recent use of MAO inhibitors (within 14 days).
- Severe hypertension or coronary artery disease.
- Asthma attacks.
- Severe liver disease.
Drug Interactions
- MAO inhibitors: Can cause a severe and potentially fatal interaction.
- Antihistamines, anticholinergics, and CNS depressants: Increased drowsiness and other CNS effects.
- Tricyclic antidepressants: Enhanced anticholinergic and pressor effects.
- Beta-blockers: May interfere with the decongestant action of phenylephrine.
- Alcohol: Increased drowsiness and impaired coordination.
- Grapefruit juice: May increase dextromethorphan levels.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Consult a physician; generally avoided unless benefits outweigh risks.
- Fetal Risks: Potential for adverse effects; data is limited.
- Breastfeeding: Excretion in breast milk unknown; use caution or consider alternatives.
Drug Profile Summary
- Mechanism of Action: Dextromethorphan: Centrally acting cough suppressant. Phenylephrine: α1-adrenergic agonist, decongestant. Triprolidine: H1-receptor antagonist, antihistamine.
- Side Effects: Drowsiness, dizziness, dry mouth, nausea, restlessness/excitement.
- Contraindications: Hypersensitivity, MAOI use, severe hypertension/CAD, asthma attacks, liver disease.
- Drug Interactions: MAOIs, antihistamines, alcohol, grapefruit juice.
- Pregnancy & Breastfeeding: Consult physician; generally avoided.
- Dosage: Adults: 5 mL every 4 hours (max 20 mL/24h). Children (6-12 years): 2.5 mL every 4 hours (max 10 mL/24h).
- Monitoring Parameters: Blood pressure, heart rate, respiratory status, mental status.
Popular Combinations
This combination itself is a popular formulation. It is not typically combined with other drugs, as it already addresses multiple symptoms.
Precautions
- General Precautions: Evaluate for underlying medical conditions, allergies, and concomitant medications.
- Specific Populations: Pregnant/breastfeeding women: Use with caution under medical supervision. Children and elderly: Monitor carefully for adverse effects.
- Lifestyle Considerations: Avoid alcohol and activities requiring alertness.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dextromethorphan Hydrobromide + Phenylephrine + Triprolidine?
A: Adults: 5 mL every 4 hours (max 20 mL/24h). Children (6-12 years): 2.5 mL every 4 hours (max 10 mL/24h). Children under 6: Consult a physician.
Q2: Can this combination be used in patients with asthma?
A: It should be avoided during acute asthma attacks and used cautiously in patients with chronic asthma.
Q3: What are the most common side effects?
A: Drowsiness, dizziness, dry mouth, nausea, and constipation.
Q4: Are there any serious drug interactions?
A: Yes, particularly with MAO inhibitors, which can lead to a potentially fatal interaction.
Q5: Can pregnant or breastfeeding women take this medication?
A: It’s generally avoided unless the potential benefits outweigh the risks. Consult a physician.
Q6: What should patients avoid while taking this medication?
A: Alcohol, operating machinery, and activities requiring alertness.
Q7: How long should a patient take this medication?
A: Only for short-term symptom relief. Consult a physician if symptoms persist for more than a week.
Q8: Can this medication be used in patients with high blood pressure?
A: Use cautiously in patients with mild to moderate hypertension. It is contraindicated in severe hypertension.
Q9: What should I do if a patient experiences an allergic reaction?
A: Discontinue the medication immediately and seek medical attention.
