Mixing DXM and Diphenhydramine
- DXM also called
- robo, robitussin, robotussin, syrup, dex, cough syrup
- Diphenhydramine also called
- benadryl, dph, sleep aid, zzzquil, unisom
Unsafe
The combination is reported to reduce the side effects of each drug and potentiate many of the recreational effects. There is a significant risk of serotonin syndrome, increased delirium, CNS depression, cognitive inhibition, risk of physical injury, hyperthermia, mania, paranoia, and psychosis, especially at higher dosages. There is an additional concern of tachycardia, hypertension, and in extreme cases, heart failure. Diphenhydramine is reported to inhibit the CYP2D6 enzyme which can increase levels of DXM. Medical dosages are not reported to be a concern. Caution is strongly recommended with this combination.
This combination carries bodily risk and can go badly psychologically. The headspace part often arrives first and makes the physical part harder to notice.
Can you mix DXM and Diphenhydramine?
Risk of serious physical or psychological harm. Not recommended under any circumstances.
TripSit drug combination chart, retrieved 2026-08-20. View the dataset.
Checking more than two?
Combinations of three or more carry risks that no pair-by-pair chart can show. The checker rates every pair at once and flags the whole-mix ones on top.
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Rated unsafe. Educational information only, not medical advice. Absence of a documented interaction is not evidence of safety.