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Dextromethorphan (DXM) is an over-the-counter (OTC) cough suppressant found in many OTC cough medicines. It is a safe and effective short-term cough remedy when used at the proper dosage. However, taking too much DXM or misusing it can lead to dangerous side effects.
- DXM is generally safe when used as directed, with only mild side effects in most cases.
- Adults shouldn’t exceed 120 mg of DXM in 24 hours. Children need much smaller doses, and DXM products should never be given to kids under 4 years old.
- Taking more than the directed dose can cause serious adverse effects (like confusion, rapid heart rate, and hallucinations) and even overdose. Never combine DXM with certain antidepressants due to the risk of serotonin syndrome, which may be life-threatening.
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Dextromethorphan (DXM) pharmacokinetics and metabolism
When DXM is taken orally, the body absorbs it through the digestive system, reaching peak levels in the blood within about 2 hours. [1][2] The liver then breaks down DXM using an enzyme called CYP2D6, turning it into another active substance called dextrorphan. [3] However, around 5–10% of people have a genetically different version of the enzyme CYP2D6 that works more slowly. This means that these people end up with higher and longer-lasting levels of DXM in their system from a typical dose. [3]
DXM and its byproducts are mostly eliminated through urine, with more than 80% cleared out within 24 hours. [4] But at very high doses, the body’s usual way of breaking down DXM (through CYP2D6) can’t keep up. This causes more DXM to accumulate in the system, reaching the brain where it blocks specific receptors (called NMDA receptors) and leading to the dissociative effects that people seek when they misuse DXM. [5]
DXM therapeutic dosage forms and guidelines
DXM is available in several forms: [1]
- Syrups
- Extended-release liquids
- Capsules
- Lozenges
All forms can work effectively if they are used correctly. The choice depends on preference and age. No matter the form, don’t use more than one DXM-containing product simultaneously. [6]
- Adults and teens (12+ years): A typical dose for a cough is 10–20 mg of DXM every 4–6 hours as needed or 30 mg every 6–8 hours, and it should not exceed 120 mg total per day. [6]
- Children 6–12 years: Much lower doses are used in children. The starting dose is usually 5 mg every 4 hours, which may be increased to 10 mg every 4 hours, and the total daily dose should not exceed 60 mg. [6]
- Children 4–6 years: Around 2.5–5 mg per dose is recommended for this age group. [6]
- Children under 4 years: DXM should not be used in children under 4 years old. [6]
Maximum daily limits
Do not exceed these maximum daily doses of DXM:
- For adults and teens, do not exceed 120 mg per day. [6][7]
- For children 6–12 years, do not exceed 60 mg per day [6]
- For children 4–6 years, do not exceed 30 mg per day. [6]
Going beyond these limits greatly increases the risk of side effects or overdose. If a cough is not improving despite the maximum dose, do not take more—seek medical advice instead.
Risks and side effects
At recommended doses, DXM is well-tolerated and usually only causes mild side effects, such as dizziness or drowsiness. [6] Serious side effects are very unlikely with regular use and doses. However, extremely high doses of DXM can cause dangerous effects that may mimic an overdose: [8]
- High blood pressure
- A rapid heartbeat
- Hallucinations
- Seizures
- Coma
A major safety concern is drug interactions. DXM should not be mixed with alcohol or other sedatives, as this can intensify sedation and breathing problems. [9] Never combine DXM with certain antidepressants (like monoamine oxidase inhibitors or selective serotonin reuptake inhibitors). This can trigger serotonin syndrome, a potentially fatal reaction caused by too much serotonin. [1]
Always check labels to avoid accidentally using multiple medicines that contain DXM. [6]
Recreational use and misuse: Taking high doses
Some people abuse DXM by taking very high doses to get high. Slang terms for this include “robo-tripping” or “skittling”. [10] This practice is dangerous. At extremely high doses, DXM acts as a hallucinogenic dissociative drug.
People who misuse it might hallucinate, but they also often become sick, including symptoms like loss of coordination and vomiting. DXM abuse leads to thousands of emergency room visits each year. [11]
Many cough medicines used to get high also contain other ingredients that can be toxic in large amounts—for example, codeine cough syrup mixtures known as Lean, Sizzurp, or Purple Drank.
DXM plateaus and risks
Recreational users describe four plateaus of DXM effects, from a mild buzz at low doses to intense hallucinations and dissociations (manifested as out-of-body experiences) at the highest doses. A higher plateau carries greater risk. [12]
Recognizing and responding to DXM overdose
A DXM overdose may cause: [13]
- Extreme drowsiness
- Confusion
- Hallucinations
- Very slow breathing
- Rapid heartbeat
- High blood pressure
- Seizures
- Coma
What to do
A DXM overdose is a medical emergency. If you suspect someone has overdosed on DXM, put them in the recovery position (on their left side) and call emergency services (like 911) immediately. You can also call Poison Control at 1-800-222-1222.
Do not wait. Fast medical treatment can be lifesaving.
Harm reduction and safety tips
There are many ways to reduce the risk of harm when using DXM. The following practical tips can help you stay safer if you choose to use DXM:
- Never combine DXM with alcohol, drugs, or other medications. Mixing greatly increases the risk of life-threatening effects.
- Use the smallest possible dose and avoid taking more too soon.
- Stay with a sober friend who can help you.
- Never drive or do anything risky while on DXM.
- If using a larger amount of DXM, do so in a comfortable environment with people you trust.
- Avoid using DXM if you have breathing/lung, liver, or heart conditions.
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