What Are Dextromethorphan and Chlorpheniramine?
To understand the safety of combining these two medications, it's important to first know what each one does individually.
The Cough Suppressant: Dextromethorphan (DM)
Dextromethorphan is an antitussive, or cough suppressant. It works by affecting the signals in the brain that trigger the cough reflex, making it effective for relieving a dry, non-productive cough. DM is commonly found in many cough syrups, capsules, and lozenges, often marketed as a long-acting cough relief ingredient. It is metabolized by the liver, and certain genetic variations or drug inhibitors can lead to prolonged effects.
The First-Generation Antihistamine: Chlorpheniramine
Chlorpheniramine is a first-generation antihistamine used to relieve symptoms caused by allergies or the common cold. It works by blocking histamine, a natural chemical in the body that can cause symptoms like sneezing, itching, and a runny or watery nose. A key characteristic of first-generation antihistamines like chlorpheniramine is their sedative property, which can cause significant drowsiness.
Risks and Side Effects of Combining These Medications
While these two drugs are frequently found together in commercial products, their combined effects can lead to amplified side effects and potential drug interactions that users must be aware of. The most common combination product for this is Coricidin HBP Cough & Cold.
Heightened Sedation and CNS Depression
Both dextromethorphan and chlorpheniramine can cause drowsiness and dizziness individually. When combined, these effects are compounded, leading to heightened central nervous system (CNS) depression. This can cause severe drowsiness, confusion, and impaired thinking, judgment, and motor coordination. These risks are especially pronounced in older adults. Due to this, anyone taking the combination should avoid driving or operating hazardous machinery until they know how the medication affects them.
Serotonin Syndrome Risk
Both chlorpheniramine and dextromethorphan have serotonergic properties, meaning they can increase serotonin levels in the brain. In therapeutic doses, this is generally not a concern, but in cases of overdose, combining the two significantly increases the risk of a potentially life-threatening condition called serotonin syndrome. The risk is also elevated when these medications are taken with other serotonergic drugs, such as certain antidepressants (e.g., SSRIs) or MAO inhibitors.
Symptoms of serotonin syndrome include:
- Rapid heart rate
- Sweating
- Muscle stiffness or spasms
- High fever
- Confusion
Other Adverse Effects
In addition to CNS depression, the combination can cause other side effects:
- Dry mouth, nose, or throat
- Constipation
- Blurred vision
- Nausea
Important Safety Precautions
- Check Active Ingredients: Always read the labels of all OTC cold and cough products before use. Many products contain the same active ingredients. Taking a combination product with DM and chlorpheniramine while also taking another product with one of those ingredients could lead to an accidental overdose.
- Avoid Alcohol: Do not consume alcohol while taking medications containing dextromethorphan and chlorpheniramine. Alcohol will intensify the sedative effects and can increase the risk of adverse reactions.
- Consult a Healthcare Provider: Before using any new medication, discuss it with your doctor or pharmacist. This is especially important for individuals with pre-existing health conditions such as glaucoma, an enlarged prostate, liver or kidney disease, or cardiovascular issues.
- Be Cautious with Other Medications: Inform your doctor or pharmacist about all other medications, including prescription drugs, vitamins, and herbal supplements. Interactions with other drugs, especially those that cause drowsiness or affect serotonin levels, can be dangerous. MAO inhibitors are specifically contraindicated.
- Follow Dosing Instructions: Never exceed the recommended dose or take the medication more frequently than directed. Use the provided measuring device for liquid formulations to ensure accuracy.
Comparison of Dextromethorphan and Chlorpheniramine
| Feature | Dextromethorphan (DM) | Chlorpheniramine |
|---|---|---|
| Primary Function | Cough Suppressant | Antihistamine |
| Symptom Relieved | Dry, non-productive cough | Sneezing, runny nose, watery eyes |
| Sedative Effect | Can cause drowsiness | Commonly causes drowsiness |
| Primary Mechanism | Works in the brain to suppress cough reflex | Blocks histamine receptors in the body |
| Key Drug Interactions | MAOIs, other serotonergic drugs, alcohol | MAOIs, other CNS depressants, alcohol |
| Common Side Effects | Dizziness, nausea, constipation | Dry mouth, blurred vision, dizziness, constipation |
| Type of Cough Treated | Primarily dry cough | Relieves cough associated with allergies/post-nasal drip |
How to Choose the Right Cold Medicine
Here are some steps to follow when selecting a cold and cough remedy:
- Identify Your Primary Symptoms: If you have a dry cough and allergy symptoms, a combination product might be suitable. If you have only one of these symptoms, a single-ingredient product might be a safer choice.
- Read the Label: Always verify the active ingredients to avoid doubling up on any one substance. Look for the product's specific warnings and age recommendations.
- Consider Time of Day: Due to the sedative effects of chlorpheniramine, a combination product is best for nighttime use. Non-drowsy alternatives are available for daytime relief.
- Talk to a Pharmacist: Pharmacists are trained to help you choose the most appropriate and safest product for your specific needs, especially if you have pre-existing health issues or take other medications.
Conclusion
In short, you can take dextromethorphan with chlorpheniramine, as they are formulated together in many over-the-counter cold and cough products. However, it is essential to proceed with caution due to the amplified sedative effects and the risk of serious drug interactions, including serotonin syndrome, especially at high doses. Always read labels carefully, avoid alcohol, and consult a healthcare professional to ensure the combination is safe for your individual health circumstances. The risks are manageable with informed use and by following all instructions. For more comprehensive information on drug interactions and medication safety, consult a reliable health resource like MedlinePlus.
