Usage
- This combination medication is prescribed for the temporary relief of cough and other symptoms associated with upper respiratory tract infections (e.g., the common cold) or allergies. These symptoms may include runny nose, sneezing, itchy or watery eyes, and itching of the nose or throat.
- Pharmacological Classification: This is a combination product containing a first-generation antihistamine (chlorpheniramine maleate) and a cough suppressant (dextromethorphan hydrobromide).
- Mechanism of Action: Chlorpheniramine provides relief from allergy symptoms by blocking the action of histamine. Dextromethorphan suppresses cough by acting on the cough center in the brain.
Alternate Names
- This combination doesn’t have a universally recognized international nonproprietary name (INN). It is often referred to simply as chlorpheniramine/dextromethorphan.
- Brand Names: Numerous brand names exist depending on the manufacturer and the specific formulation. Some examples include (note that formulations may contain additional active ingredients like phenylephrine): Coricidin HBP Cough & Cold, Dimetapp Children’s Long-Acting Cough Plus Cold, NoHist DM, Robitussin, Tussin DM.
How It Works
- Pharmacodynamics: Chlorpheniramine competes with histamine for H1-receptor sites, reducing the effects of histamine release. Dextromethorphan acts centrally in the medulla to suppress the cough reflex. It has no analgesic or addictive properties.
- Pharmacokinetics:
- Absorption: Chlorpheniramine is well-absorbed from the gastrointestinal tract. Dextromethorphan is also readily absorbed orally.
- Metabolism: Both drugs are primarily metabolized in the liver, primarily by CYP2D6 for dextromethorphan and also involving CYP3A4 for chlorpheniramine.
- Elimination: Both drugs are primarily eliminated in the urine, as metabolites. The elimination half-life of chlorpheniramine is around 20-40 hours and about 2-4 hours for dextromethorphan.
- Mode of Action: Chlorpheniramine acts as an inverse agonist at the H1 histamine receptor. Dextromethorphan acts primarily as an NMDA receptor antagonist and also interacts with sigma opioid receptors and serotonin and norepinephrine transporters.
- Elimination Pathways: Primarily renal excretion. Hepatic metabolism via CYP2D6 (dextromethorphan) and CYP3A4 (chlorpheniramine) is significant.
Dosage
Standard Dosage
Adults:
- Tablets/Capsules: 4 mg chlorpheniramine / 30 mg dextromethorphan every 4-6 hours as needed. Do not exceed 24 mg chlorpheniramine or 120 mg dextromethorphan in 24 hours.
- Syrup/Liquid: Dosage varies depending on the concentration of the specific product. Refer to product labeling for instructions.
Children:
- Not recommended for children under 6 years of age, unless under the direction of a physician.
- 6 to 12 years old: Dosage varies depending on the product and formulation. Consult product labeling or a physician. Chewable tablets, syrups, or liquids may be available for easier administration.
Special Cases:
- Elderly Patients: Start with a lower dose and monitor for side effects like confusion and urinary retention.
- Patients with Renal Impairment: Use with caution. Dose adjustment may be needed.
- Patients with Hepatic Dysfunction: Use with caution. Dose adjustment may be needed.
- Patients with Comorbid Conditions: Use with caution in patients with glaucoma, prostatic hypertrophy, cardiovascular disease, hyperthyroidism, and asthma.
Clinical Use Cases
The combination of chlorpheniramine and dextromethorphan isn’t typically employed in the specific clinical settings listed (intubation, surgical procedures, mechanical ventilation, ICU, emergency situations). Its primary use remains in outpatient management of cough and cold symptoms due to allergies or upper respiratory tract infections.
Dosage Adjustments
Dose adjustments are based on age, kidney function, and liver function, and should be individualized based on patient response and potential side effects.
Side Effects
Common Side Effects
- Drowsiness
- Dizziness
- Dry mouth, nose, and throat
- Blurred vision
- Constipation
- Restlessness or excitability (especially in children)
Rare but Serious Side Effects
- Allergic reactions (rash, itching, swelling, severe dizziness, trouble breathing)
- Seizures
- Tachycardia
- Hallucinations
- Difficulty urinating
Long-Term Effects
No specific long-term effects associated with short-term use are generally reported.
Adverse Drug Reactions (ADR)
ADRs primarily relate to excessive anticholinergic effects or hypersensitivity reactions and require appropriate management.
Contraindications
- Hypersensitivity to chlorpheniramine or dextromethorphan
- Narrow-angle glaucoma
- Urinary retention
- Severe cardiovascular disease
- Concurrent or recent use of monoamine oxidase inhibitors (MAOIs)
Drug Interactions
- MAOIs
- Alcohol
- CNS depressants (sedatives, tranquilizers, hypnotics)
- Tricyclic antidepressants
- Anticholinergic drugs
- Other medications metabolized by CYP2D6 (e.g., certain antidepressants, antipsychotics)
Pregnancy and Breastfeeding
- Pregnancy: Limited data available. Use only when clearly needed and after careful risk/benefit assessment.
- Breastfeeding: Chlorpheniramine and dextromethorphan can pass into breast milk. Potential for adverse effects in infants, including drowsiness, irritability, and decreased milk supply. Use with caution and at the lowest effective dose. Non-sedating antihistamines may be preferable.
Drug Profile Summary
- Mechanism of Action: Chlorpheniramine: H1 receptor inverse agonist (antihistamine). Dextromethorphan: Centrally acting cough suppressant.
- Side Effects: Drowsiness, dizziness, dry mouth, blurred vision, constipation.
- Contraindications: Hypersensitivity, MAOI use, narrow-angle glaucoma, urinary retention.
- Drug Interactions: MAOIs, alcohol, CNS depressants, tricyclic antidepressants.
- Pregnancy & Breastfeeding: Use with caution; potential for adverse infant effects.
- Dosage: Age-dependent; refer to detailed dosage guidelines above.
- Monitoring Parameters: Clinical response, side effects (especially in elderly and those with comorbidities).
Popular Combinations
This combination is sometimes included in multi-ingredient cold and flu preparations that also contain decongestants (e.g., phenylephrine, pseudoephedrine) and/or analgesics/antipyretics (e.g., acetaminophen).
Precautions
- Pre-existing medical conditions (asthma, glaucoma, prostatic hypertrophy, cardiovascular disease, hyperthyroidism)
- Use in elderly, children, pregnant/breastfeeding women as noted above.
- Avoid alcohol.
- May impair alertness; caution with operating machinery or driving.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Chlorpheniramine Maleate + Dextromethorphan Hydrobromide?
A: Refer to detailed dosage section above. Dosing depends on age, formulation, and individual patient factors.
Q2: Can this medication be used in children?
A: Not generally recommended for children under 6 years old. Pediatric dosing should be guided by a physician.
Q3: What are the most common side effects?
A: Drowsiness, dizziness, dry mouth/nose/throat, blurred vision, constipation.
Q4: Can I take this medication if I’m pregnant or breastfeeding?
A: Consult a physician. Use with caution if benefits outweigh risks.
Q5: Are there any drug interactions I should be aware of?
A: Yes, avoid concurrent use of MAOIs, alcohol, and other CNS depressants. Several other drug interactions are possible.
Q6: What should I do if I miss a dose?
A: Take the missed dose as soon as you remember. If it’s almost time for the next dose, skip the missed dose. Do not double the dose.
Q7: Can I drive while taking this medication?
A: Use caution, as drowsiness and dizziness can occur.
Q8: How long can I take this medication?
A: This medication is intended for short-term use. Consult your doctor if symptoms persist beyond a week.
Q9: What should I do if my symptoms worsen or don’t improve?
A: Consult your physician.
