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Toxicology – Dextromethorphan (DXM) Toxicity
Source
Dextromethorphan is a synthetically produced compound found in many over-the-counter cough and cold medications, available in both liquid and tablet forms.
Typical Presentation
Misuse often involves ingestion of large quantities of cough syrup or tablets, particularly among adolescents. Patients may present with confusion, disorientation, or abnormal behavior following excessive intake.
Clinical Features
Effects are dose-dependent. At therapeutic levels, DXM acts as a cough suppressant. In higher doses, it can produce euphoria, agitation, hypertension, tachycardia, hyperthermia, sweating, hallucinations, and dissociative states. Severe toxicity may result in unresponsiveness and sensory detachment. When combined with serotonergic agents such as SSRIs or MAO inhibitors, serotonin syndrome may develop.
Mechanism of Action
DXM is metabolized into dextrorphan, its active metabolite. This compound acts on sigma opioid receptors to suppress cough. At higher doses, it blocks NMDA receptors and inhibits reuptake of monoamines, leading to dissociative and sympathomimetic effects. Unlike traditional opioids, it does not significantly affect μ or δ receptors, so classic opioid toxicity is not typically observed.
Management
Treatment is primarily supportive. Naloxone may provide partial benefit in some cases, although its effects are variable.
Key Points
Source
Dextromethorphan is a synthetically produced compound found in many over-the-counter cough and cold medications, available in both liquid and tablet forms.
Typical Presentation
Misuse often involves ingestion of large quantities of cough syrup or tablets, particularly among adolescents. Patients may present with confusion, disorientation, or abnormal behavior following excessive intake.
Clinical Features
Effects are dose-dependent. At therapeutic levels, DXM acts as a cough suppressant. In higher doses, it can produce euphoria, agitation, hypertension, tachycardia, hyperthermia, sweating, hallucinations, and dissociative states. Severe toxicity may result in unresponsiveness and sensory detachment. When combined with serotonergic agents such as SSRIs or MAO inhibitors, serotonin syndrome may develop.
Mechanism of Action
DXM is metabolized into dextrorphan, its active metabolite. This compound acts on sigma opioid receptors to suppress cough. At higher doses, it blocks NMDA receptors and inhibits reuptake of monoamines, leading to dissociative and sympathomimetic effects. Unlike traditional opioids, it does not significantly affect μ or δ receptors, so classic opioid toxicity is not typically observed.
Management
Treatment is primarily supportive. Naloxone may provide partial benefit in some cases, although its effects are variable.
Key Points
- Many DXM-containing products also include acetaminophen, so levels should be checked in suspected overdose.
- DXM is sometimes misused as a recreational substance and marketed as an alternative to other psychoactive drugs.
- Certain formulations (e.g., combination cold medications) are commonly abused for their DXM content.
- Chronic use may lead to bromide toxicity, particularly with tablet formulations.
- DXM can cause false-positive results for PCP on urine drug screens.
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