Box 1: “Plateaus” of dextromethorphan toxicity*,2,3.
Plateau 0
Total dose 20mg to 45mg.
You can barely feel it at all, but it relieves cough.
Plateau 0.5
Total dose 45mg to 100mg
Antidepressant effects (especially when stacked with 100mg of Wellbutrin SR)
Plateau 1 (1.5–2.5
mg/kg)
Total intake 100–200
mg (4–6 capsules or 35–60 mL of syrup)
Restlessness, euphoria
Plateau 2 (2.5–7.5
mg/kg)
Total dose 200–500
mg (7–
18 capsules or 60–185 mL of syrup)
Exaggerated auditory and visual sensations, closed-eye hallucinations, imbalance
Plateau 3 (7.5–15
mg/kg)
Total dose 500–1000
mg (
18–33 capsules or 185–375 mL of syrup)
Visual and auditory disturbances, altered consciousness, delayed reaction times, mania, panic, partial dissociation
Plateau 4 (> 15
mg/kg)
Total dose > 1000
mg (> 33 capsules or > 375 mL of syrup)
Hallucinations, delusions, ataxia, complete dissociation
*Assuming a 75-kg person, 30-
mg capsules and 3
mg per millilitre of syrup.
