Norketamine: The Active Metabolite in Ketamine Tablets

Norketamine is the primary breakdown product your liver creates when it processes ketamine, and it retains meaningful activity at the same NMDA (N-methyl-D-aspartate) receptor that ketamine targets, the receptor complex most linked to ketamine's rapid effects on mood and dissociation. Because oral ketamine tablets pass through the liver before reaching the bloodstream, they generate a much larger share of norketamine relative to the parent drug than intravenous (IV) or intranasal (IN) ketamine does. That shift in the ketamine-to-norketamine ratio is one of the main pharmacological reasons oral tablets tend to feel different, often less intensely dissociative and slower to peak, than infusions or nasal spray.

How your body turns ketamine into norketamine

After you swallow a compounded ketamine tablet, it dissolves and is absorbed from the gastrointestinal tract or, with sublingual formulations, partly through tissue under the tongue. Ketamine absorbed through the gut wall travels to the liver via the portal vein before it ever reaches general circulation, a routing step called first-pass metabolism. Liver enzymes, chiefly cytochrome P450 3A4 (CYP3A4) and CYP2B6, convert a large fraction of that ketamine into norketamine through a process called N-demethylation.

This is the core reason oral ketamine has lower bioavailability than injectable or nasal forms, a meaningful portion of the dose is converted to norketamine (and further metabolites) before it can act on the brain. For background on how absorption route drives these differences, see our explainer on ketamine bioavailability explained why sublingual administration matters.

Does norketamine cause the dissociative or antidepressant effects?

Norketamine does bind NMDA receptors, but preclinical research generally reports it as a weaker antagonist than ketamine, commonly cited as roughly one-third to one-fifth as potent, depending on the study. On its own, that would suggest norketamine plays a smaller role than ketamine in producing acute dissociative effects. But because oral tablets generate comparatively more norketamine relative to ketamine than IV or intranasal dosing does, norketamine's cumulative exposure, measured as area under the concentration-time curve, can end up contributing more to the overall drug effect with oral dosing than with faster routes.

Researchers have also proposed a further layer: ketamine and norketamine are metabolized again into hydroxynorketamine (HNK) compounds, including (2R,6R)-HNK. Some investigators have described a shift from what they call the "ketamine paradigm", where ketamine and norketamine were assumed to drive effects, toward a "ketamine metabolite paradigm," in which HNK is examined as a possible contributor to antidepressant activity with less dissociative and psychotomimetic effect in animal models. This work is largely preclinical and early-stage human research; it has not been established as clinical fact for oral ketamine tablets in people, and you should treat it as an active area of investigation rather than settled science.

What this means for how your tablet feels and how long it lasts

The practical takeaway for someone on a prescribed tablet protocol is that oral ketamine's onset is slower and its peak effect is generally gentler than IV or intranasal ketamine, partly because a smaller fraction of the original dose reaches your bloodstream as intact ketamine, and partly because norketamine and its own metabolites clear more slowly. That combination can produce a longer, flatter effect curve rather than a sharp peak. If you want a fuller picture of the timeline, see how long does ketamine tablet stay in your system.

Absorption of oral ketamine is also sensitive to what's in your stomach. Food, antacids, and the specific compounded formulation can all change how much ketamine and norketamine your body produces from the same nominal dose, see food antacids oral ketamine absorption and how food affects ketamine tablet absorption for the specifics. Because tablets are compounded rather than FDA-approved for depression, formulation and pharmacy quality can also affect how consistently ketamine and its metabolites are absorbed dose to dose, a question worth raising directly with your compounding pharmacy, covered in our guide to pharmacy questions.

Tablets versus other routes: where metabolites matter most

If you're comparing a tablet protocol against troches or infusions, the metabolite question is one input among several, absorption route, bioavailability, and monitoring needs also differ. Troches (lozenges held under the tongue) can bypass some first-pass metabolism through sublingual absorption, shifting the ketamine-to-norketamine ratio compared to swallowed tablets; see what are ketamine troches for how that formulation works. For a broader look at how the published evidence base for oral routes compares with infusion and intranasal data, read oral ketamine safety and efficacy the evidence.

None of this is a reason to adjust your dose on your own. Only esketamine (Spravato), delivered as a nasal spray, holds FDA approval for treatment-resistant depression. Oral ketamine tablets are prescribed off-label and dispensed by compounding pharmacies, which is why dosing decisions, including how a prescriber accounts for metabolite exposure, should stay inside a supervised, prescriber-managed protocol.