Dextromethorphan (DXM) is a medication commonly used as a cough suppressant. It belongs to a class of drugs known as antitussives, which are substances that suppress coughing. As an over-the-counter (OTC) medication, dextromethorphan is widely available in various cough and cold preparations. It is important to understand its pharmacology, therapeutic uses, potential side effects, and interactions to use it safely and effectively.

Pharmacology of Dextromethorphan

Dextromethorphan works primarily on the central nervous system to suppress the urge to cough. It acts on the cough center in the brain, specifically the medulla oblongata, and inhibits the cough reflex. Unlike codeine, another common cough suppressant, dextromethorphan does not possess significant analgesic (pain-relieving) or addictive properties.

The exact mechanism of action of dextromethorphan is not completely understood, but it is believed to involve the inhibition of N-methyl-D-aspartate (NMDA) receptors, which play a role in neurotransmission. Additionally, dextromethorphan has sigma-1 receptor agonist properties, contributing to its antitussive effects.

Therapeutic Uses

Dextromethorphan is primarily indicated for the relief of cough due to various respiratory conditions, such as the common cold, bronchitis, and other upper respiratory tract infections. It is often included in combination with other active ingredients, such as decongestants or antihistamines, to provide comprehensive symptom relief in cough and cold medications.

Forms and Dosage

Dextromethorphan is available in different formulations, including syrups, capsules, and lozenges. The dosage varies depending on the specific product and the age of the individual. It is crucial to follow the dosing instructions provided on the medication packaging or as directed by a healthcare professional. Taking more than the recommended dose can lead to adverse effects and is considered misuse.

Side Effects of Dextromethorphan

While dextromethorphan is generally well-tolerated when used appropriately, it can cause side effects in some individuals. Common side effects may include:

  1. Dizziness: Dextromethorphan can cause dizziness, especially at higher doses. It is advisable to avoid activities that require alertness, such as driving or operating machinery, until the individual’s response to the medication is known.
  2. Drowsiness: Some people may experience drowsiness after taking dextromethorphan. This effect can be exacerbated when combining the medication with other substances that cause sedation, such as alcohol or certain antihistamines.
  3. Nausea and Vomiting: In some cases, dextromethorphan may cause gastrointestinal upset, leading to nausea and vomiting. Taking the medication with food or a glass of milk can help alleviate this side effect.
  4. Confusion: High doses of dextromethorphan, often associated with misuse or abuse, can lead to confusion and hallucinations. This is more likely to occur when exceeding the recommended dosage.
  5. Allergic Reactions: While rare, allergic reactions to dextromethorphan can occur. Signs of an allergic reaction may include rash, itching, swelling, severe dizziness, or difficulty breathing. If any of these symptoms occur, medical attention should be sought immediately.

It’s important to note that misuse of dextromethorphan, often seen in attempts to achieve euphoria or altered states of consciousness, can lead to more severe side effects, including dissociation, hallucinations, and even a potentially life-threatening condition known as serotonin syndrome.

Interactions with Other Medications

Dextromethorphan can interact with various medications, and it is crucial to be aware of potential drug interactions to avoid adverse effects. Some notable interactions include:

  1. Monoamine Oxidase Inhibitors (MAOIs): Combining dextromethorphan with MAOIs, a class of antidepressants, can lead to a potentially serious condition known as serotonin syndrome. This syndrome is characterized by symptoms such as confusion, hallucination, seizure, extreme changes in blood pressure, increased heart rate, fever, excessive sweating, shivering or shaking, blurred vision, muscle spasm or stiffness, tremor, incoordination, stomach cramp, nausea, vomiting, and diarrhea.
  2. Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs): These are other classes of antidepressants that, when combined with dextromethorphan, can increase the risk of serotonin syndrome.
  3. Quinidine: Dextromethorphan should be used cautiously with quinidine, as the combination can increase the risk of dextromethorphan toxicity.
  4. CYP2D6 Inhibitors: Dextromethorphan is metabolized by the CYP2D6 enzyme in the liver. Drugs that inhibit this enzyme, such as certain antidepressants and antipsychotics, can increase dextromethorphan levels in the body, potentially leading to adverse effects.
  5. Alcohol and CNS Depressants: Combining dextromethorphan with alcohol or other central nervous system (CNS) depressants can enhance the sedative effects of both substances, leading to increased drowsiness and impaired coordination.

Before taking dextromethorphan, individuals should inform their healthcare provider about all medications, including prescription, over-the-counter, and herbal supplements, to ensure there are no potential interactions.

Special Populations

  1. Pregnancy and Breastfeeding: The safety of dextromethorphan during pregnancy and breastfeeding is not well-established. Pregnant or breastfeeding individuals should consult with their healthcare provider before using dextromethorphan.
  2. Pediatric and Geriatric Populations: Dextromethorphan is generally considered safe for use in children when administered at appropriate doses. However, dosing should be carefully monitored, and it is advisable to consult with a pediatrician before giving dextromethorphan to children. The use of dextromethorphan in the geriatric population should also be approached with caution, considering factors such as renal and hepatic function.


Dextromethorphan is a widely used and effective cough suppressant available over the counter. When used responsibly and as directed, it can provide relief from cough associated with various respiratory conditions. However, it is essential for individuals to be aware of potential side effects, drug interactions, and contraindications. Misuse or abuse of dextromethorphan can lead to serious consequences, including hallucinations, confusion, and, in extreme cases, life-threatening conditions. As with any medication, it is advisable to consult with a healthcare professional for personalized guidance, especially when there are concerns about potential interactions with other medications or underlying health conditions.

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