Mixing Ketamine (ket) and NyQuil
Dangerous
High risk of death or life-changing injury. Do not combine.
What 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 take Ketamine with NyQuil?
NyQuil contains acetaminophen, DXM and doxylamine. The most concerning part is Ketamine with NyQuil (Doxylamine): each makes the other stronger: people pass out without warning, and ketamine can push diphenhydramine into delirium. Do not combine at recreational doses. If someone passes out, put them on their side. The doxylamine in NyQuil is checked as diphenhydramine (Benadryl), the closest drug MixSafe has data for, so this answer and any dose in it are diphenhydramine's. MixSafe rates Ketamine with NyQuil as "Dangerous" — high risk of death or life-changing injury. Do not combine. Sources: the Drug Facts labels on DailyMed, the TripSit combination chart and MixSafe research. Educational information, not medical advice.
What is in it
- NyQuil
- Acetaminophen + DXM + Doxylamine. Doxylamine is checked as diphenhydramine (Benadryl): both are sedating antihistamines of the same kind. NyQuil Severe also contains phenylephrine, a decongestant MixSafe has no data for.
Ingredient by ingredient
Ketamine + NyQuil (Doxylamine)Dangerous
The doxylamine in NyQuil is checked as diphenhydramine (Benadryl), the closest drug MixSafe has data for, so this answer and any dose in it are diphenhydramine's.
Each makes the other stronger: people pass out without warning, and ketamine can push diphenhydramine into delirium. Do not combine at recreational doses. If someone passes out, put them on their side.
Both substances potentiate the ataxia and sedation caused by the other and can lead to unexpected loss of consciousness at high doses. While unconscious, vomit aspiration is a risk if not placed in the recovery position. Ketamine has a high likelihood of increasing DPH's deliriant effects at higher dosages and can greatly increase the risk of injury, mania, and psychosis. Medical dosages of both substances are unlikely to cause concern.
Source: TripSit drug combination chart
Ketamine + NyQuil (DXM)Low risk, increased effect
Low risk of harm, but the effects amplify each other. Doses that are fine alone can be far too much together.
Both substances primarily exert their effects through NMDA antagonism. Currently, there is no evidence regarding mechanisms that might reduce these effects.
Source: TripSit drug combination chart
Ketamine + NyQuil (Acetaminophen)Low risk, no synergy
Neither substance is expected to meaningfully change the other. Both still carry their own individual risks.
No specific interaction is documented. Acetaminophen's main risk is dose-dependent liver injury, so the thing to watch in any combination is total daily intake across all products (roughly 4g/24h) and anything else straining the liver.
Sources: Prescott LF. Paracetamol, alcohol and the liver. Br J Clin Pharmacol. 2000 · Acetaminophen: A Liver Killer or Thriller
- Vicks NyQuil Cold & Flu LiquiCaps, Drug Facts label. DailyMed, December 2025. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=efe4e649-7514-32dd-e053-2995a90a0492
Ingredient lists checked 2026-09-27. Formulas change and store brands differ, so the Drug Facts box on your own packet is the final word.
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