What Are the Ingredients in Ketamine?

Ketamine’s active ingredient is a single molecule, ketamine hydrochloride, but the full list of what goes into a ketamine product depends heavily on the formulation. An injectable vial from a hospital pharmacy, a compounded lozenge from a telehealth provider, and an illicitly manufactured powder each contain very different supporting ingredients, preservatives, and potential contaminants. The chemistry of the molecule itself is straightforward, yet the surrounding ingredients raise questions that matter for safety and effectiveness.

The Active Molecule

Ketamine is a synthetic compound built around a cyclohexanone ring bonded to a chlorine-bearing phenyl ring and a methylamino group. In pharmaceutical products, it appears as ketamine hydrochloride, meaning the base molecule is paired with hydrochloric acid to form a water-soluble salt. This is the form that dissolves readily for injection or absorption through mucous membranes.

One detail that trips people up is that ketamine actually exists as two mirror-image versions of the same molecule, called enantiomers. The S-form (esketamine) and the R-form (arketamine) have identical atoms arranged in opposite spatial orientations. Most pharmaceutical ketamine is a 50/50 mixture of both, known as the racemic form. Esketamine is roughly three times more potent as a painkiller and about one and a half times stronger as an anesthetic compared to arketamine, which is why it was developed separately and approved as a nasal spray (Spravato) for treatment-resistant depression.¹ When someone asks “what’s in ketamine,” the enantiomer question is worth knowing because the two forms do not behave identically in the body.

Excipients in Injectable Formulations

A vial of injectable ketamine is not pure ketamine hydrochloride dissolved in nothing. It contains excipients, the inactive ingredients that keep the solution stable, sterile, and safe to inject. The most common carrier is sterile water or normal saline (0.9% sodium chloride solution). Some formulations are prepared with sodium chloride to match the tonicity of blood, making them less painful to inject.²

The more controversial excipient is benzethonium chloride, a preservative found in many multi-dose ketamine vials intended for both human and veterinary use. Benzethonium chloride prevents microbial growth in vials that are punctured more than once. The problem is that this preservative is not pharmacologically inert. Research has shown it binds to numerous receptors and transporters in the brain, and some scientists have raised the concern that it could contribute to effects typically attributed to ketamine itself.³ Not every ketamine product contains it. Single-use vials and preservative-free formulations skip benzethonium chloride entirely. If you are receiving ketamine infusions at a clinic, the choice of preservative-free versus preserved vials is a detail worth asking about.

Why the Preservative Matters

Benzethonium chloride has drawn scrutiny beyond its receptor-binding activity. In animal studies, repeated epidural injections of ketamine containing benzethonium chloride produced signs of nerve damage in rabbits, raising flags about neurotoxicity when the preservative contacts neural tissue directly.⁴ Laboratory work on cell cultures found that benzethonium chloride increased the toxic effects of ketamine on lymphoma cells and neuroblastoma cells, pushing cell death rates substantially higher than ketamine alone.⁵

These findings do not mean that every ketamine injection is dangerous. The concern is specific to routes where the preservative contacts nerve tissue directly, like epidural or intrathecal administration, and to repeated or chronic exposure. For a single intravenous infusion using a preserved vial, the clinical significance is less clear. Still, the research has pushed many compounding pharmacies and infusion clinics toward preservative-free formulations, and it is one reason the FDA-approved esketamine nasal spray does not contain benzethonium chloride.

What Goes Into Compounded Ketamine Products

The booming market for at-home ketamine therapy has introduced a range of non-injectable formulations that contain a much longer ingredient list than a simple vial. Compounded troches (lozenges that dissolve in the mouth), sublingual tablets, and nasal sprays are prepared by compounding pharmacies, and each format requires its own set of inactive ingredients.

A typical ketamine troche recipe calls for ketamine hydrochloride blended with several supporting ingredients: silica gel (a flow agent that prevents clumping), stevia (a sweetener to mask the intensely bitter taste), acacia (a natural gum used as a binder), and citric acid (for flavor and pH adjustment). These powders are mixed and incorporated into a melted base, often a polyethylene glycol or hard-fat base, that gives the troche its shape and controls how quickly it dissolves.⁶

Because compounding pharmacies operate under different regulatory oversight than manufacturers of FDA-approved drugs, the exact inactive ingredients can vary from one pharmacy to the next. One pharmacy might use stevia as a sweetener while another uses sucralose. The base material might differ. Flavoring agents like mint or citrus oils are common additions. If you have allergies or sensitivities, it is worth requesting the full ingredient list from the compounding pharmacy rather than assuming all troches are identical.

What Ketamine Becomes Inside Your Body

Once ketamine enters your bloodstream, liver enzymes begin transforming it into a cascade of breakdown products. These metabolites are, in a real sense, additional “ingredients” your body encounters during treatment, and some of them are biologically active.

The primary metabolic step is removal of a methyl group, converting ketamine into norketamine. This reaction is carried out mainly by the liver enzyme CYP3A4. Norketamine is not a dead-end waste product. It crosses into the brain and retains roughly one-fifth to one-third the potency of ketamine itself, which helps explain why the effects of ketamine persist even as blood levels of the parent drug drop.⁷ This is especially relevant during long infusions or repeated dosing, where norketamine accumulates and contributes meaningfully to both the painkilling and the dissociative effects.

From norketamine, the body produces several hydroxylated metabolites by adding oxygen-containing groups to the cyclohexanone ring. Among these, hydroxynorketamine (HNK) has attracted intense research interest. Animal studies found that certain HNK forms produce antidepressant-like effects on their own, without the dissociation or sedation that ketamine causes.⁸ Brain tissue analysis after ketamine administration has confirmed that norketamine, multiple forms of hydroxynorketamine, and additional metabolites are all present in the brain simultaneously.⁹

The practical upshot is that ketamine’s effects are not produced by a single molecule acting alone. Your body converts it into a family of related compounds, each with its own activity profile. Researchers are still working out exactly how much of ketamine’s antidepressant benefit comes from the parent drug versus its metabolites, and this remains one of the most active questions in the field.

How Ketamine Acts on the Brain

Ketamine’s best-known target is the NMDA receptor, a type of glutamate receptor involved in learning, memory, and neural plasticity. By blocking this receptor, ketamine disrupts normal signaling patterns in ways that produce dissociation, pain relief, and, at sub-anesthetic doses, rapid antidepressant effects. But NMDA receptors are not the whole story. Research has identified interactions with opioid receptors, specifically mu opioid receptors, which adds a layer of complexity to understanding both ketamine’s therapeutic effects and its potential for misuse.¹⁰

This multi-target action is relevant to the “ingredients” question because it means ketamine’s effects cannot be reduced to one simple receptor interaction. The molecule, along with its metabolites, engages several different systems in the brain simultaneously. When you add in the preservative benzethonium chloride, which also binds brain receptors, the pharmacological picture of “what’s in a ketamine infusion” becomes more complex than most patients realize.

Impurities in Illicitly Manufactured Ketamine

Street ketamine is a different product from pharmaceutical ketamine, and its ingredient list reflects that. Illicit manufacturing introduces byproducts that would never appear in a regulated product. A large-scale analysis of 150 seized ketamine samples identified 17 characteristic manufacturing impurities. All of these shared a chemical backbone related to deschloroketamine but carried additional substituents like extra chlorine atoms, hydroxyl groups, methyl groups, and more complex ring structures.¹¹

The synthesis routes used in clandestine labs also differ from pharmaceutical manufacturing. One common illicit approach starts from a precursor called 2-(2-chlorophenyl)-2-nitrocyclohexanone, reduces it to norketamine using zinc powder and formic acid, and then converts norketamine to ketamine using formaldehyde and formic acid. This process is popular because it is fast and requires relatively small amounts of chemicals.¹² The trade-off is that each shortcut in synthesis can leave behind residual reagents, unreacted precursors, and novel byproducts whose safety profiles are completely unknown.

For anyone using ketamine outside a medical setting, the impurity question is not academic. These byproducts have not been tested for toxicity, and their presence varies from batch to batch. Drug-checking services that use mass spectrometry can detect some of these contaminants, but many users have no access to such testing.

Ketamine Mixed With Other Drugs in Clinical Settings

In emergency departments and operating rooms, ketamine is sometimes mixed with other medications before administration. The most common combination is ketamine with propofol, sometimes nicknamed “ketofol.” The idea is to balance ketamine’s dissociative effects with propofol’s sedation, potentially getting smoother sedation with fewer side effects from either drug alone. Studies have confirmed that mixtures of propofol and ketamine at standard ratios remain physically stable in a syringe for at least six hours at room temperature.¹³

More complex admixtures have also been tested. When propofol, ketamine, and opioids like fentanyl or remifentanil are mixed together, the ketamine and remifentanil remain chemically stable for up to 24 hours. However, combinations with fentanyl showed variable recovery of both propofol and fentanyl, hinting at possible degradation.¹⁴ These compatibility details matter to clinicians who need to know whether a pre-mixed syringe will still contain the intended drug concentrations by the time it is used. For patients, the relevance is simpler: the “ingredients” in your ketamine sedation may include more than just ketamine, and those combinations are studied for chemical stability before they reach your IV line.

Experimental Formulations on the Horizon

One of ketamine’s limitations is that its effects wear off quickly. Intravenous ketamine has a short half-life, which is useful for anesthesia but inconvenient for treating depression, where patients often need to return for repeat infusions every few weeks. Researchers have been experimenting with sustained-release formulations to extend the drug’s duration.

One approach uses lipid-based particles to encapsulate ketamine and release it slowly. In animal testing, a sustained-release lipid formulation extended ketamine’s half-life by roughly 27-fold compared to a standard intravenous dose, while also tripling overall drug exposure and reducing how quickly the body cleared it.¹⁵ The ingredients in such a formulation include the lipid carrier materials in addition to ketamine itself, creating a product with a very different ingredient profile from anything currently on the market. These formulations are still in early development, but they illustrate how the “ingredients in ketamine” question will keep evolving as new delivery technologies mature.

Reading a Ketamine Product Label

If you are prescribed ketamine in any form, the label or accompanying documentation should list both the active ingredient (ketamine hydrochloride, with the concentration in milligrams per milliliter for liquids or milligrams per unit for solids) and the inactive ingredients. For an injectable vial, you will typically see water for injection, possibly sodium chloride, and a preservative if it is a multi-dose vial. For a compounded product, the ingredient list is longer and more variable.

A few things to look for: whether the product contains benzethonium chloride (relevant if you are receiving neuraxial administration or frequent infusions), whether the compounding pharmacy uses any ingredients you are allergic to, and the concentration of ketamine itself. Compounded products come in a wide range of strengths, and a 100 mg troche is a very different experience from a 200 mg troche even though the inactive ingredients might be identical. The route of administration also changes what matters. A troche that you hold in your mouth exposes your oral tissues to every inactive ingredient for several minutes, while an IV formulation bypasses the mouth entirely. Patients with oral sensitivities or conditions like mucositis should pay particular attention to what is in a sublingual or buccal product.

Ketamine’s ingredient story is ultimately a story about context. The same active molecule appears in products ranging from a sterile hospital vial with two ingredients to a flavored lozenge with half a dozen, to an illicit powder carrying unknown manufacturing residues. What surrounds the ketamine hydrochloride changes based on the formulation, the manufacturer, and the intended route, and those surrounding ingredients can have their own biological effects that are only beginning to be understood.