Mixing DXM (robo) and Diphenhydramine (Benadryl)
Unsafe
Diphenhydramine raises DXM levels, and together they risk serotonin syndrome, delirium, overheating and heart strain. Avoid this combination at recreational doses.
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.
Headspace vs physical riskWhat to do
- Say what was taken and how much.Responders need it, and in most US states Good Samaritan laws protect both of you from drug possession charges when you call for an overdose.
- Unresponsive: put them on their side, tilt the head back, and stay until help arrives.Never leave someone alone to “sleep it off”.
- Never Use Alone 1-800-484-3731Stays on the line and sends help if you stop responding.
- Full steps: what to do if it is already happeningOverdose signs, the recovery position, what to say on the call, and whether you can be charged for making it.
- Poison Control 1-800-222-1222Free and 24/7, for “is this bad?” before it becomes an emergency.
Can you mix DXM (robo) and Diphenhydramine (Benadryl)?
MixSafe rates mixing DXM and Diphenhydramine as "Unsafe" — risk of serious physical or psychological harm. Not recommended under any circumstances. Source: TripSit drug combination chart, retrieved 2026-08-20. Educational information, not medical advice.
- DXM
- Cold medicines often add acetaminophen or an antihistamine — check the label
- DXM also called
- robo, robitussin, robotussin, syrup, dex, cough syrup
- Diphenhydramine also called
- benadryl, dph, sleep aid, zzzquil, unisom, doxylamine
TripSit drug combination chart, retrieved 2026-08-20. View the dataset.
Think this rating or note is wrong, or know a better source? Send it.
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.
Open this in the checkerRelated combinations
Rated unsafe. Educational information only, not medical advice. Absence of a documented interaction is not evidence of safety.