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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Chlorpheniramine/phenylephrine
Brand Name
Ed A-hist
Generic Name
Chlorpheniramine/phenylephrine
Active Ingredient
ChlorpheniramineCategory
Nonsteroidal Anti-inflammatory Drug [EPC]
Salt Form
Maleate
Variants
1
Different strengths and dosage forms
| Strength | Form | Route | NDC |
|---|---|---|---|
| 4 mg/5mL | LIQUID | ORAL | 0485-0155 |
Detailed information about Ed A-hist
This page is for informational purposes only and does not replace medical advice. Before using any prescription or over-the-counter medication for Ed A-hist, you must consult a qualified healthcare professional.
Chlorpheniramine is a first-generation alkylamine antihistamine used to relieve symptoms of allergic rhinitis, urticaria, and the common cold by blocking H1 receptors. It is known for its potent anti-allergic properties and significant sedative effects.
For adults and adolescents aged 12 years and older, the standard dosing for Chlorpheniramine Maleate is as follows:
Chlorpheniramine must be dosed with extreme caution in children. The FDA and manufacturers provide specific age-based guidelines:
Because the metabolites of Chlorpheniramine are excreted by the kidneys, patients with significant renal (kidney) impairment may require lower doses or extended dosing intervals. While specific GFR-based (Glomerular Filtration Rate) guidelines are not always standardized for this older medication, clinicians typically monitor these patients closely for signs of increased sedation or anticholinergic toxicity.
Chlorpheniramine is extensively metabolized by the liver. In patients with hepatic (liver) disease, the half-life of the drug can be significantly prolonged. Healthcare providers may recommend starting at the lowest possible dose (e.g., 2 mg) and increasing the interval between doses to prevent drug accumulation and toxicity.
Patients aged 65 and older are particularly sensitive to the effects of Chlorpheniramine. The American Geriatrics Society's 'Beers Criteria' lists first-generation antihistamines as potentially inappropriate for older adults. If used, doses should be kept to the absolute minimum, as the risk of confusion, dizziness, and falls is substantially higher in this population.
To ensure the best results and minimize risks, follow these instructions:
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and return to your regular schedule. Never 'double up' or take two doses at once to make up for a missed one, as this significantly increases the risk of overdose.
An overdose of Chlorpheniramine can be life-threatening, particularly in children. Signs of overdose may include:
In the event of a suspected overdose, contact your local poison control center or seek emergency medical attention immediately.
> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance. If your symptoms do not improve within 7 days, or if you develop a fever, consult a doctor.
Because Chlorpheniramine is a first-generation antihistamine, it has a high incidence of side effects, primarily related to its impact on the central nervous system and its anticholinergic properties. The most common experiences include:
These effects are still frequently reported and should be monitored:
Rare but documented reactions include:
> Warning: Stop taking Chlorpheniramine and call your doctor immediately if you experience any of these.
While Chlorpheniramine is generally intended for short-term use, some patients take it chronically for perennial allergies. Potential long-term concerns include:
No FDA black box warnings for Chlorpheniramine. However, it carries significant warnings regarding its use in pediatric populations and its sedative effects when combined with alcohol or other CNS depressants.
Report any unusual symptoms to your healthcare provider. If you notice a change in your mood or behavior, or if side effects become intolerable, discuss alternative treatments (such as second-generation antihistamines) with your doctor.
Chlorpheniramine is a potent medication that affects multiple systems in the body. The most critical safety point is the risk of Central Nervous System (CNS) depression. Because this drug crosses the blood-brain barrier, it causes significant impairment of mental alertness and physical coordination. Patients must be aware that their ability to perform complex tasks may be compromised even if they do not 'feel' excessively sleepy.
There are currently no FDA black box warnings for Chlorpheniramine. It is considered safe for over-the-counter use when label instructions are followed precisely. However, the absence of a black box warning does not imply a lack of risk; the drug's profile necessitates several major precautions.
While Chlorpheniramine is used to treat allergies, it is possible (though rare) to be allergic to the drug itself or the maleate salt. If you develop a rash, itching, or swelling after taking it, discontinue use immediately.
Patients with a history of Asthma or COPD (Chronic Obstructive Pulmonary Disease) should use Chlorpheniramine with caution. The drug's anticholinergic effect can thicken bronchial secretions, making it more difficult to clear the airways during an exacerbation. It may also reduce the volume of secretions, leading to a 'dry' cough that is harder to manage.
Chlorpheniramine can cause tachycardia (rapid heart rate) and palpitations. Individuals with high blood pressure, heart disease, or a history of arrhythmias should consult a cardiologist before use. It may also interact with medications used to treat these conditions.
Due to its anticholinergic properties, Chlorpheniramine can increase intraocular pressure. It is contraindicated in patients with narrow-angle glaucoma. Furthermore, it can cause urinary hesitancy. Men with Benign Prostatic Hyperplasia (BPH) or other bladder neck obstructions may find that the drug makes it significantly harder to urinate.
For occasional OTC use, formal lab monitoring is rarely required. However, for patients using Chlorpheniramine long-term or those with underlying health issues, healthcare providers may monitor:
DO NOT drive a car, operate heavy machinery, or engage in hazardous activities until you know how Chlorpheniramine affects you. The impairment caused by first-generation antihistamines has been compared in clinical studies to the impairment caused by alcohol consumption. Even if you feel 'fine,' your reaction times may be significantly slowed.
Alcohol consumption must be strictly avoided while taking Chlorpheniramine. Alcohol synergistically increases the sedative effects of the antihistamine, leading to dangerous levels of CNS depression, respiratory depression, and a high risk of accidents or injury.
There is no specific 'withdrawal syndrome' associated with Chlorpheniramine; however, stopping the drug suddenly after long-term use may result in a 'rebound' of allergy symptoms. If you have been taking it daily for several weeks, your doctor may suggest gradually tapering the dose while transitioning to a non-sedating antihistamine.
> Important: Discuss all your medical conditions, including any history of glaucoma, enlarged prostate, or thyroid problems, with your healthcare provider before starting Chlorpheniramine.
Certain medications should never be combined with Chlorpheniramine due to the risk of life-threatening interactions:
Chlorpheniramine can interfere with the results of allergy skin tests. Because the drug suppresses the body's reaction to allergens, the skin test may show a 'false negative' (no reaction even if an allergy exists). Patients are typically advised to stop taking antihistamines at least 3 to 7 days before undergoing allergy skin testing. It may also occasionally interfere with certain urine drug screens, potentially causing false positives for other substances; always inform the lab of your current medications.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including those used for sleep, anxiety, or pain management.
Chlorpheniramine must NEVER be used in the following circumstances:
In these cases, a healthcare provider must perform a careful risk-benefit analysis:
Patients who are allergic to other antihistamines in the alkylamine class (such as brompheniramine or dexchlorpheniramine) are highly likely to be allergic to Chlorpheniramine. There is also a small risk of cross-sensitivity with other first-generation antihistamines. If you have a known allergy to any antihistamine, consult your allergist before starting Chlorpheniramine.
> Important: Your healthcare provider will evaluate your complete medical history, including any history of breathing problems or digestive obstructions, before prescribing or recommending Chlorpheniramine.
Chlorpheniramine is generally classified as Pregnancy Category B. This means that animal reproduction studies have failed to demonstrate a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women.
Chlorpheniramine is excreted in breast milk in small amounts. There are two primary concerns:
As discussed in the dosage section, Chlorpheniramine is approved for children 2 years and older, but with significant caveats. It is not recommended for children under 2. In pediatric patients, the risk of 'paradoxical excitation' is high; children may become hyperactive, agitated, and unable to sleep. There is also a risk of accidental overdose when using multi-ingredient cold products. Always consult a pediatrician before giving this medication to a child.
In patients over 65, Chlorpheniramine is associated with a significantly increased risk of:
Because of these risks, second-generation antihistamines are almost always preferred for geriatric patients.
In patients with a GFR below 50 mL/min, the clearance of Chlorpheniramine metabolites is reduced. While specific dose-reduction tables are not standard, a common approach is to increase the dosing interval from every 4-6 hours to every 8-12 hours. The drug is not significantly removed by hemodialysis.
Patients with cirrhosis or other forms of liver failure (Child-Pugh Class B or C) will have a significantly longer drug half-life. In these individuals, the drug can accumulate to toxic levels quickly. Healthcare providers typically recommend a 50% dose reduction or avoiding the drug entirely in favor of an antihistamine that is not as dependent on hepatic metabolism.
> Important: Special populations require individualized medical assessment. Never share your medication with others, especially children or the elderly.
Chlorpheniramine is a competitive H1-receptor antagonist. It binds to H1 receptors on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract. By blocking these receptors, it prevents the physiological effects of histamine release. Unlike newer antihistamines, Chlorpheniramine also has a high affinity for muscarinic acetylcholine receptors. This 'off-target' binding is responsible for its anticholinergic effects, such as drying of the nasal mucosa and the potential for side effects like dry mouth and urinary retention.
The onset of action for Chlorpheniramine is relatively rapid, with effects typically beginning within 30 to 60 minutes of oral administration. The duration of effect for a single immediate-release dose is usually 4 to 8 hours, although the biological half-life suggests that some level of receptor occupancy persists much longer. There is a clear dose-response relationship regarding both symptom relief and sedation; higher doses provide better allergy control but significantly more CNS impairment.
| Parameter | Value |
|---|---|
| Bioavailability | 25% to 50% (due to high first-pass metabolism) |
| Protein Binding | 70% to 72% |
| Half-life | 14 to 30 hours (Adults); 10 to 13 hours (Children) |
| Tmax | 2 to 6 hours |
| Metabolism | Hepatic (Primarily CYP2D6) |
| Excretion | Renal (Metabolites and <5% unchanged drug) |
Chlorpheniramine is classified as a First-Generation Antihistamine within the Alkylamine subclass. Related medications in this same class include brompheniramine (Dimetapp) and triprolidine. It is distinct from the Ethanolamine class (like diphenhydramine/Benadryl) and the Piperazine class (like hydroxyzine/Atarax).
Common questions about Ed A-hist
Chlorpheniramine is primarily used to relieve symptoms of the common cold and upper respiratory allergies. It is highly effective at reducing sneezing, a runny nose, and itchy or watery eyes caused by hay fever or pet dander. Additionally, it is used to treat skin-related allergic reactions such as hives (urticaria) and itching. Because it has drying effects, it is a common ingredient in multi-symptom cold and flu medications. Healthcare providers may also recommend it for mild allergic reactions to insect bites or stings.
The most frequent side effect of Chlorpheniramine is significant drowsiness or sleepiness, which affects a large percentage of users. Other common side effects include dry mouth, dry nose, and a dry throat due to its anticholinergic properties. Some people may also experience blurred vision, constipation, or a feeling of dizziness. In some cases, particularly in children, it can cause 'paradoxical excitation,' leading to nervousness or restlessness instead of sleepiness. Most of these effects are temporary and will resolve once the medication leaves your system.
No, you should strictly avoid alcohol while taking Chlorpheniramine. Both alcohol and Chlorpheniramine are central nervous system (CNS) depressants, meaning they slow down brain activity. When taken together, they can dangerously increase sedation, dizziness, and impairment of motor skills. This combination significantly increases the risk of accidents, falls, and respiratory depression. Even a small amount of alcohol can trigger an extreme reaction when combined with this antihistamine.
Chlorpheniramine is generally considered one of the safer antihistamines to use during pregnancy and is classified as Category B. It has been used for decades without a clear link to birth defects in human studies. However, it should only be used when the benefits clearly outweigh the potential risks to the fetus. It is especially important to avoid using it near the end of the third trimester, as it may affect the newborn. Always consult your obstetrician or healthcare provider before starting any medication while pregnant.
Chlorpheniramine typically begins to work within 30 to 60 minutes after you take it orally. You will likely notice a reduction in sneezing and itching during this timeframe. Peak levels of the medication in your bloodstream are usually reached between 2 and 6 hours after dosing. The effects of a standard immediate-release dose generally last for about 4 to 6 hours. Extended-release versions are designed to provide relief for up to 12 hours.
Yes, you can generally stop taking Chlorpheniramine suddenly without experiencing dangerous withdrawal symptoms. Unlike some other classes of medications, it does not cause physical dependence. However, if you have been taking it daily to manage chronic allergies, you may notice that your allergy symptoms (like sneezing and runny nose) return quickly once you stop. If you find you need an antihistamine every day, your doctor may suggest switching to a long-acting, non-drowsy alternative. Always discuss long-term medication use with a healthcare professional.
If you miss a dose of Chlorpheniramine, you should take it as soon as you remember. However, if it is almost time for your next scheduled dose, it is better to skip the missed dose entirely and continue with your regular schedule. You should never take two doses at the same time to 'catch up,' as this increases the risk of excessive sedation and other side effects. If you are taking the medication only 'as needed' for symptoms, you can simply take the next dose when symptoms return. Monitoring your dosing schedule is important to avoid exceeding the 24-hour maximum limit.
Weight gain is not a commonly reported side effect of short-term Chlorpheniramine use. However, some studies have suggested that long-term use of certain first-generation antihistamines might be associated with increased appetite or weight changes in some individuals. This is thought to be due to the drug's effect on histamine receptors in the brain that help regulate hunger. If you notice significant weight changes while taking this medication, you should discuss it with your doctor. Most people using it for seasonal allergies will not experience this issue.
Chlorpheniramine can interact with many other medications, so caution is necessary. It should never be taken with MAO inhibitors, and you must be very careful when combining it with other drugs that cause sleepiness, such as opioid pain relievers, anxiety medications, or muscle relaxants. It can also interact with certain antidepressants and blood pressure medications. Because many over-the-counter cold products contain multiple ingredients, you must check labels to ensure you aren't 'doubling up' on antihistamines. Always provide your doctor or pharmacist with a full list of your current medications.
Yes, Chlorpheniramine is widely available as a generic medication and is typically very affordable. It is sold under many different store brands as 'Allergy Relief' or 'Chlorpheniramine Maleate 4mg.' You can find it in various forms, including tablets, liquids, and extended-release capsules. Because it is an older medication, the generic versions are considered just as effective as the original brand-name products. It is also a very common component in generic multi-symptom cough and cold formulations.
Other drugs with the same active ingredient (Chlorpheniramine)