DXM is dextromethorphan, a cough suppressant found in dozens of over-the-counter cold and flu medications. It’s one of the most widely available drugs in any pharmacy, sold under brand names like Robitussin, Vicks DayQuil Cough, NyQuil, Delsym, and many store-brand equivalents. At recommended doses, it safely suppresses coughs. At much higher doses, it produces dissociative and hallucinogenic effects, which is why it has a long history of recreational misuse, particularly among teenagers and young adults.
How DXM Works in the Body
DXM is structurally related to codeine and other opioids, but it doesn’t act like a traditional painkiller. Instead, it suppresses the cough reflex by acting on nerve pathways in the brainstem that control coughing. It blocks a specific type of receptor in the brain involved in excitatory signaling, and it also activates a protein that helps regulate how excitable nerve cells are. Together, these effects quiet the cough reflex without producing the pain-relieving or breathing-suppressing effects typical of opioids.
DXM also increases serotonin activity in the brain by slowing the reabsorption of serotonin between nerve cells. This is the same basic mechanism used by common antidepressants, and it’s the reason DXM can be dangerous when combined with certain medications.
Where You’ll Find It
DXM is the active ingredient in a wide range of cough products. Some of the most recognized include Robitussin, Vicks Formula 44, Vicks DayQuil Cough, Delsym, Triaminic Long Acting Cough, PediaCare Long-Acting Cough, and Zicam Cough Max. It’s also included in many combination cold medicines alongside acetaminophen, antihistamines, or decongestants. This matters because people who misuse DXM by drinking large quantities of combination syrups may unknowingly take toxic amounts of those other ingredients, especially acetaminophen, which can cause fatal liver damage.
Recreational Misuse and “Plateaus”
DXM misuse is sometimes called “robotripping” or “skittling.” Users describe four distinct levels of intoxication, often referred to as plateaus, based on the amount consumed. These ranges assume a person weighing roughly 75 kilograms (165 pounds).
- Plateau 1 (100 to 200 mg): Mild stimulation, restlessness, and euphoria. This is roughly 4 to 6 standard capsules or 35 to 60 mL of cough syrup.
- Plateau 2 (200 to 500 mg): Exaggerated sounds and visuals, closed-eye hallucinations, and loss of balance. About 7 to 18 capsules or 60 to 185 mL of syrup.
- Plateau 3 (500 to 1,000 mg): Significant visual and auditory disturbances, altered consciousness, mania, panic, slowed reaction times, and partial dissociation from reality.
- Plateau 4 (over 1,000 mg): Full hallucinations, delusions, severe loss of coordination, and complete dissociative states where users lose awareness of their body and surroundings.
The jump between a therapeutic dose and a recreational one is significant. A normal adult cough dose is around 10 to 30 mg every few hours. Plateau 3 and 4 doses are 15 to 30 times higher. At these levels, the risk of dangerous side effects rises sharply, including dangerously high body temperature, seizures, and loss of consciousness.
Why Genetics Change the Experience
Your body breaks down DXM primarily through a liver enzyme called CYP2D6. Most people metabolize the drug quickly, and only about 1 to 2 percent of it actually reaches the bloodstream in active form. But roughly 5 to 10 percent of people of European descent (and smaller percentages in other populations) are “poor metabolizers,” meaning their version of this enzyme works slowly or barely at all. In poor metabolizers, roughly 80 percent of the drug reaches the bloodstream intact.
This means two people taking the exact same dose can have wildly different experiences. A poor metabolizer taking what they consider a moderate recreational dose could end up with blood levels many times higher than expected, greatly increasing the risk of toxicity.
The Serotonin Syndrome Risk
Because DXM boosts serotonin activity, combining it with other drugs that do the same thing can push serotonin levels to dangerous heights. This condition, called serotonin syndrome, is potentially life-threatening. The medications most likely to interact include SSRIs (common antidepressants like escitalopram and fluoxetine), MAO inhibitors, tricyclic antidepressants, and certain opioid painkillers.
Serotonin syndrome typically shows up as a combination of three problems: the nervous system goes into overdrive (rapid heart rate, sweating, fever), mental state changes (agitation, confusion, restlessness), and muscles become hyperactive (twitching, exaggerated reflexes, rigidity). Mild cases may resolve on their own, but severe cases can involve dangerously high body temperature and organ failure. The hallmark sign that distinguishes serotonin syndrome from other conditions is involuntary rhythmic muscle contractions, particularly in the legs.
This interaction is especially risky because both DXM and SSRIs are processed by the same liver enzyme. When they compete for that enzyme, each drug lingers in the body longer, amplifying the other’s effects.
DXM and Drug Testing
A common concern is whether taking DXM will cause a failed drug test. Despite its structural similarity to opioids, a standard immunoassay urine screen is unlikely to flag DXM as a positive for opioids or other substances at normal or even double the recommended dose. A study testing young adults found that all urine screens came back negative for opioids six hours after taking both a standard dose and twice the standard dose. At very high recreational doses, however, some point-of-care tests have been reported to produce false positives for PCP, since DXM and PCP share some pharmacological overlap. A confirmatory lab test can easily distinguish the two.
Legal Status
DXM is not a controlled substance under federal law in the United States. It is legal to purchase without a prescription. However, many states have passed laws restricting sales to minors, typically requiring buyers to be at least 18 years old. Some retailers voluntarily enforce age checks as well. Despite periodic discussions about reclassifying DXM, it remains unscheduled and widely available as of 2025.