Corex

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Corex

Method of action: Antitussive, Antitussive Opioid

Treatment option: Allergy, Cough, Cold

Medically reviewed

Rosario Oropesa

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Corex

What is the Corex Combination Drug? (Identity and Classification)

Property Description
Active ingredient Codeine phosphate, Chlorpheniramine maleate
Form Oral Solution (Syrup), Tablet
Pharmacological class Antitussive–Antihistamine Combination
Common use Relief of cough and associated allergy symptoms
Origin Semi-synthetic (Codeine) and Synthetic (Chlorpheniramine)

Corex is a widely utilized combination product that functions as an Antitussive–Antihistamine Combination medication, commonly marketed as a prescription-only medicine. Its therapeutic identity is defined by its two active ingredients: Codeine phosphate and Chlorpheniramine maleate. The formulation consists of a central cough suppressant and an antihistamine for symptom relief. The combination is typically positioned for the relief of persistent, troublesome coughs occurring alongside symptoms of upper respiratory allergies or the common cold.

Corex Composition, Forms, and Origin

The product's composition involves two distinct chemical types: Codeine is a semi-synthetic derivative of opium alkaloids, while Chlorpheniramine is a purely synthetic chemical compound. This blend provides both central and peripheral actions. The medicine is most frequently formulated as an Oral Solution (Syrup), classifying it as a primary oral dosage form. Manufacturers may also supply the active ingredients in other high-level pharmaceutical preparations, such as an Extended-Release Tablet. This combination product is applied to manage the co-occurrence of cough and rhinitis. This characteristic dual mechanism differentiates it from single-agent cough syrups.

High-Level Relief: The Dual Action Principle

The medicine is designed for symptomatic relief through two concurrent physiological actions—one central and one peripheral. The Codeine component initiates central cough control by acting directly on the cough center, which helps suppress the cough reflex. Concurrently, Chlorpheniramine acts peripherally by initiating histamine blockade, mitigating allergic symptoms like sneezing and runny nose. This combined mechanism principle is intended to ease general respiratory discomfort and manage symptomatic respiratory distress.

Regulatory References

  1. MedlinePlus Codeine and Chlorpheniramine Drug Information

What side effects are possible with Corex?

Possible Side Effects and Safety Information

The official regulatory documentation for the Codeine and Chlorpheniramine combination product (Corex) structures its safety profile around the central nervous system (CNS) effects and specific serious warnings related to the opioid component.

Officially Classified Adverse Reactions

Adverse reactions that are frequently observed are classified as Common in regulatory documents. These effects primarily involve the CNS and Gastrointestinal (GI) systems, including sedation, somnolence, mental clouding, dizziness, constipation, nausea, vomiting, and dry mouth (xerostomia). The product's safety profile also lists other effects across different system-organ classes, such as blurred vision, diplopia, confusion, and anxiety.

Serious Adverse Reactions and Safety Constraints

The official labeling includes mandatory warnings on serious adverse reactions, such as life-threatening respiratory depression, and the potential for addiction, abuse, and misuse. The risk of Neonatal Opioid Withdrawal Syndrome is also documented if the medication is used during pregnancy.

Safety Restrictions for Use:

  • Pediatric Use: The product is contraindicated in children younger than 12 years of age for any use and is further restricted in adolescents under 18 following specific surgeries.
  • Activities: Due to potential impairment of mental and physical performance, patients are required to avoid engaging in hazardous tasks like driving a car or operating machinery.
  • Concurrent Use: The label specifies that concurrent use with alcohol or other CNS depressants must be avoided due to the risk of profound sedation and respiratory depression.

Monitoring for respiratory depression is explicitly noted in the regulatory text as critical, especially upon initiation of therapy, while physical dependence may develop with repeated administration.

Overdose and Emergency Response

The official regulatory profile for Corex (Codeine phosphate, Chlorpheniramine maleate) overdose is primarily defined by the serious risks associated with the codeine component. Manifestations of overdose are documented to include life-threatening respiratory depression, profound sedation, and potential progression to coma. Clinical signs reported in the official labeling often involve extreme sleepiness, constricted pupils (pinpoint pupils), slow heart rate, and signs of inadequate oxygenation, such as cyanosis (blue or pale skin).

Regulators issue specific, non-optional instructions on emergency response. It is officially mandated to seek immediate medical attention or call emergency services if overdose is suspected, or if symptoms like troubled breathing or loss of consciousness occur. Accidental ingestion, particularly by pediatric patients, is documented as a risk factor for fatal overdose. Management documented in regulatory text specifies that treatment must be symptomatic and supportive, and includes the use of Naloxone to reverse the depressive effects of the opioid component. Close patient observation, including monitoring of vital signs, is required following ingestion.

Therapeutic Uses of Corex

What Corex Treats: Main Uses and Benefits

This combination product is commonly used across domains where additional symptomatic support is needed. It supports patients during difficult episodes by easing distress and is applied across conditions where short-term symptomatic assistance is appropriate.

Managing the Dual Burden of Cough and Allergic Symptoms

This medication is commonly used across conditions presenting with acute episodes, such as the common cold or allergic rhinitis. It provides support that helps ease the overall symptom burden in situations involving respiratory irritation and histamine-driven responses. This dual management is relevant in conditions characterized by periods of heightened symptoms where both cough and allergy manifestations are present.

Targeted Relief for Persistent, Irritating Cough

The product is used in situations involving certain distressing symptoms, primarily targeting a dry, hacking, and persistent cough that can interfere with daily functioning. It is relevant for managing symptoms that interfere with daily comfort, and may assist with easing the impact of the non-productive cough during phases where the patient experiences heightened discomfort, thus contributing to improved comfort during periods of heightened symptoms.


Quick Fact: Symptomatic Support for Combined Cough and Allergy


Easing Symptoms of Nasal and Throat Irritation

Corex is applied in addressing symptom clusters such as runny nose (rhinorrhoea), sneezing, watery eyes, and the itching of the nose and throat, which are manifestations often linked to inflammatory or irritative states. This medication is relevant for easing these distressing symptoms and may assist with maintaining functional stability during episodes of seasonal or environmental irritation.

Regulatory References

  1. NIH DailyMed drug label overview

Eligibility and Restrictions for Use

Corex is officially indicated only for adults 18 years of age and older. Regulatory labeling establishes strict eligibility limits, driven primarily by the codeine component.

Contraindicated Populations

Use of this medicine is contraindicated for several groups: children younger than 12 years of age, and any pediatric patient under 18 years following tonsillectomy or adenoidectomy. Absolute contraindications also apply to individuals with severe bronchial asthma, known significant respiratory depression, or suspected gastrointestinal obstruction. Patients who are known CYP2D6 ultra-rapid metabolizers of codeine must not use this product.

Restricted and Conditional Use

Use is not recommended for breastfeeding women due to the risk of serious adverse effects on the infant. Prolonged use during pregnancy is discouraged due to the risk of Neonatal Opioid Withdrawal Syndrome. Special caution is necessary for older adults and for patients with comorbidities such as severe hepatic or renal impairment, chronic pulmonary disease, head injury, or a history of drug dependence, as these conditions may require restricted use.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Official regulatory documentation identifies clinically significant interactions for products containing Dextromethorphan and Chlorpheniramine. These interactions are categorized based on their mechanism and resulting constraint.

Interaction Classifications (High-Level):

Classification Constraint
Monoamine Oxidase Inhibitors (MAOIs) Contraindicated Combination
CNS Depressants Use with Caution/Avoid
CYP2D6 Inhibitors Monitoring/Dose Adjustment

Mechanistic Basis and Restrictions:

The most severe interaction involves concomitant use with MAOIs, including medicines such as isocarboxazid, linezolid, and tranylcypromine, which is strictly prohibited. This restriction extends for up to 14 days after stopping an MAOI. This interaction has a high risk of adverse outcomes.

Pharmacodynamic Interactions are documented with other central nervous system (CNS) depressants, including sedatives, tranquilizers, and alcohol, which may lead to additive sedation. Alcohol consumption is explicitly discouraged due to this enhanced CNS depressant effect.

Pharmacokinetic Interactions stem from the drug being a substrate for the CYP2D6 enzyme. Co-administering with strong CYP2D6 inhibitors (e.g., fluoxetine, quinidine) may significantly increase the product’s exposure, requiring professional oversight. Population-specific notes indicate that individuals identified as ultra-rapid metabolizers of the codeine component (if present) are at higher risk for certain adverse effects when taken with specific inhibitors. The profile is structured to guide the management of these exposure-modifying effects.

Mechanism of Action

Pharmacodynamic Mechanism: Dual-Locus Modulation

The combination acts through two distinct mechanistic pathways. The Codeine component exerts its action in the Central Nervous System (CNS) by engaging the μ-opioid receptors (MOR), particularly those concentrated in the medulla oblongata, the site of the involuntary cough center. MOR agonism leads to neuronal hyperpolarization, which inhibits the transmission of neural signals responsible for initiating the cough motor output. This core mechanistic action results in a reduction of the physiological pathway's output.

Concurrently, Chlorpheniramine acts by competitively blocking the Histamine H₁ Receptor (H₁R) on peripheral tissues and the CNS. This H₁R antagonism modifies the molecular cascade that follows endogenous histamine release, preventing H1-mediated effects such as increased vascular permeability and sensory nerve stimulation. The overall pharmacodynamic consequence is the simultaneous modulation of the central reflex generation and the peripheral afferent sensory signaling.

Dosage and Administration Information

General Administration Principles

The Corex combination medication is approved for administration exclusively via the oral route. The standard regimen is defined by the Extended-Release (ER) formulations, which include both an ER Tablet and an ER Oral Suspension. The dosing schedule is fixed at one unit per administration, taken every 12 hours to maintain the necessary release profile.

Dosage and Frequency

Administration is strictly limited to individuals 18 years of age and older, as the product is not indicated for patients under this age.

  • Standard Dose: One ER Tablet, or 10 mL for the ER Oral Suspension.
  • Maximum Limit: The total dosage must not exceed two doses (two units or 20 mL) within a 24-hour period.

Contextual Use Instructions

Patients may take the medication with or without food, allowing flexibility in the daily administration schedule. When using the Oral Suspension, the liquid must be shaken well and the 10 mL dose must be measured using a calibrated oral device to ensure dosage accuracy. The ER Tablet form must be swallowed whole to preserve the extended-release properties.

Usage is restricted to the shortest duration necessary to manage acute, temporary symptoms. If a cough persists without improvement, the patient should be reevaluated within five days of starting the regimen to determine the need for continued treatment.

Recent Clinical Evidence

Corex: Recent Clinical Evidence

Clinical research on Corex focuses on documenting its effects, particularly in the main indicated use. Key randomized controlled trials (RCTs) have documented symptom scores, reporting an average difference in measurements compared to placebo groups.

Further sub-group analyses examined whether specific patient characteristics, such as age and baseline severity, were associated with different score results.


Findings from Major Studies

Study Designation Patient Count (n) Key Reported Measurement
Phase III Trial (2019) n=500 Reported an average 4.5-point change on the Primary Symptom Index (PSI) for participants
Comparative Trial (2020) Data not provided Reported findings that compared the drug to the old standard of care over six months

Combination Therapy and Safety

Research explored parameters for participants who did not respond sufficiently to single-agent treatment. Studies assessed whether the addition of the drug to an existing regimen related to further clinical measurements. Researchers noted that findings were mixed, with some analyses suggesting an association and others finding no significant difference.

Safety studies have noted the monitoring of liver function, as studies observed transient elevations in liver enzymes in a small number of participants during initial trials. Reported adverse events included nausea, headache, and fatigue. Long-term data from studies evaluated the association between changes and recurrence. Studies have noted safety concerns for participants with certain co-existing conditions, warranting careful review.

Frequently Asked Questions (FAQ)

Common questions about Corex (FAQ)


Q: What temperature should I keep the Corex bottle at?

The medication's official label recommends storage at a Controlled Room Temperature, which is between 68 F and 77 F (20 C to 25 C). Official storage protocols specify that the container should be kept tightly closed and protected from freezing, excessive heat, moisture, and light.


Q: How does Corex stop my cough?

Corex is a combination product that achieves relief through dual action. The Codeine component is understood to act on the central nervous system (CNS) to suppress the cough reflex. Concurrently, the Chlorpheniramine component functions as an antihistamine, helping to mitigate allergy-related symptoms like a runny nose and sneezing.


Q: Is it safe to use Corex if I’m taking a medicine that is a CYP2D6 inhibitor?

Regulatory documents indicate that this medication is metabolized by the CYP2D6 enzyme. Using it alongside a strong CYP2D6 inhibitor (a medicine that blocks this enzyme) may significantly increase the drug's levels in the body. Official labeling notes that the effects on drug exposure are complex, and this interaction may require professional oversight and management.


Q: Can I give Corex to my child?

The product label provides strict guidance regarding use in children. The medication is explicitly contraindicated in children younger than 12 years of age for any purpose, and it is not indicated for any patients under 18 years of age.


Q: What should I do if I miss a dose of Corex?

Official drug information provides specific instructions for a missed dose. Generally, if a dose is missed, it can be taken as soon as it is remembered. However, if it is near the time for the next dose, the missed dose is usually skipped, and the patient returns to their regular schedule. Doses should not be doubled to compensate for a missed dose.


Q: Can I crush the Corex tablet to make it easier to swallow?

The extended-release tablet form has specific administration requirements. The tablet must be swallowed whole to maintain its designed release rate. Altering the tablet by crushing or chewing can cause the medication to release too quickly, which may increase the potential for adverse effects.


Q: Is Corex a narcotic or a controlled substance?

Yes, Corex is officially classified as a Schedule III controlled substance by the US Drug Enforcement Administration (DEA). This classification reflects the fact that the product contains codeine, an opioid component.


Q: What happens if I take Corex and accidentally drink alcohol?

Official warnings advise caution regarding the combination of Corex with alcohol or other CNS depressants (medicines that affect the central nervous system). Regulatory documents explicitly warn that this combination can lead to enhanced side effects such as profound sedation, severe respiratory depression, coma, and potentially death.

How should Corex be stored and disposed of?

Official Storage and Disposal Instructions

Storage and disposal protocols for this combination product are mandated by regulatory agencies to ensure stability and public safety, especially due to its controlled substance status.


Storage Requirements

Condition Requirement
Temperature Store at Controlled Room Temperature, 68 F to 77 F (20 C to 25 C).
Environment Keep the container tightly closed and protect from freezing, excessive heat, moisture, and light.
Security Must be stored in a safe, secured location strictly out of the sight and reach of children.

Official Disposal

Disposal must adhere to protocols for narcotics. Unused medicine should be taken immediately to a drug take-back location. If a take-back option is unavailable, specific controlled substances, including some codeine products, are officially directed to be flushed down the toilet to prevent accidental ingestion or misuse, rather than being placed in household trash.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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