Converting IV Ketamine Dose to Oral Equivalent

There is no validated milligram-for-milligram formula for converting an intravenous (IV) ketamine dose into an oral equivalent dose, and no prescriber should calculate one by simple math alone. The two routes differ too much in how completely the drug reaches the bloodstream and in how the body breaks it down for a direct ratio to hold up in practice. This matters most to people comparing clinic-based IV ketamine infusions against take-home oral options, or evaluating whether a lower oral dose can realistically substitute for a known IV dose that worked for them.

Why Bioavailability Breaks a Simple Conversion

When ketamine is given intravenously, the entire dose enters the bloodstream directly, which is why IV administration is treated as 100% bioavailable in pharmacology. Swallowed ketamine takes a very different path: it is absorbed through the gut and passes through the liver before reaching systemic circulation, a process called first-pass metabolism. That liver pass breaks down a large share of the dose before it can act on the brain, which is why published pharmacokinetic estimates put oral ketamine's bioavailability at roughly 16% to 24%, with meaningful variation from person to person based on liver enzyme activity and individual metabolism.

On its face, that gap might suggest a simple fix: divide the IV dose by the oral bioavailability percentage to find a "matching" oral dose. In practice, this ignores a second variable that matters just as much as the raw percentage absorbed. You can compare how quickly each route takes effect in the ketamine onset time by route of administration guide, and how concentration differs by route in the peak plasma concentration ketamine by route breakdown.

Metabolite Differences Complicate the Math Further

First-pass metabolism does not just reduce the amount of ketamine available, it also converts more of the dose into norketamine, a metabolite with its own activity at NMDA receptors. The ratio of ketamine to norketamine circulating in the blood is noticeably higher after oral dosing than after IV dosing, which means an oral dose scaled to match IV ketamine's plasma concentration will still expose the body to a different mix of compounds. The ketamine metabolites norketamine hydroxynorketamine guide covers how this metabolite shift can influence both effects and side effects. Elimination also differs by route, which is detailed in the ketamine half-life by route guide, and matters for how often a dose needs to be repeated.

What Oral Ketamine Protocols Actually Look Like

Rather than converting from an IV dose, clinicians who prescribe oral ketamine off-label for conditions like depression or chronic pain typically start at a low, conservative dose and adjust it over subsequent visits based on how the person responds and tolerates side effects. Compounding pharmacies prepare oral ketamine as capsules, liquid, or troches, and the compounded ketamine safety oversight guide explains how those formulations are regulated and quality-checked. Because oral ketamine is taken without the direct supervision required for IV or intramuscular dosing in many settings, it is usually reserved for people who have already tolerated ketamine under supervision; the ketamine routes requiring in-clinic supervision guide lays out which routes call for that oversight and why.

No oral ketamine formulation currently holds FDA approval for depression or any psychiatric condition. The only ketamine-derived medication with that approval is esketamine (Spravato), a nasal spray approved by the FDA in 2019 specifically for treatment-resistant depression under a restricted distribution program. Oral ketamine for mental health use remains off-label, which means dosing decisions rest on clinical judgment and published case evidence rather than a manufacturer-established protocol.