Ketamine Pharmacokinetics

Plasma concentration model for intranasal and oral ketamine. Unique among recreational drugs — also used clinically for treatment-resistant depression and anaesthesia at higher doses.

⚠ Ketamine-induced uropathy — the most important chronic harm. Regular ketamine use causes progressive, irreversible bladder damage. Ketamine cystitis presents as severe bladder pain, urinary frequency, and reduced bladder capacity. In severe cases, bladder removal has been required. This is not a dose-dependent acute risk but a chronic use risk — it can develop within months of regular use. There is no safe frequency established. Any sign of urinary symptoms in a ketamine user requires immediate medical attention.

Population-average PK model. Ketamine is a racemic mixture (R and S enantiomers) with different potencies — clinical esketamine (S-ketamine, Spravato) is approximately 2× more potent at the same plasma concentration. Street ketamine is racemic. Individual CYP3A4 variation affects clearance.

Personal details

Body weight

Dose schedule

First dose👃 intranasal

Amount: 60mg(typical recreational line ~30–100mg)

10mg300mg

Total: 60mg(0.86 mg/kg)

SHOW8h

0–40 ng/mL Sub-threshold40–100 ng/mL Mild — analgesia, light dissoc.100–200 ng/mL Moderate dissociation200–400 ng/mL Strong — k-hole territory400–400+ ng/mL ⚠ Anaesthetic dissociation

Clinical vs recreational context: Ketamine is a licensed anaesthetic and, as esketamine (Spravato), an antidepressant for treatment-resistant depression. Clinical IV anaesthetic doses are typically 1–2 mg/kg (70–140mg for 70kg). Recreational intranasal doses are typically 30–100mg. The k-hole starts to become possible above ~100mg intranasally for a non-tolerant user.

Oral route produces different effects: First-pass metabolism converts ketamine to norketamine — an active metabolite with a longer half-life and different profile. Oral ketamine produces a more prolonged, less intense effect than intranasal. This is why the same dose taken orally feels weaker but lasts longer.

Dangerous combinations

Alcohol / CNS depressantsSEVERE

Both cause CNS and respiratory depression. Ketamine alone maintains airway reflexes — combined with alcohol this protection is reduced. Risk of respiratory depression and aspiration (vomiting while dissociated). The most common cause of ketamine-related emergency presentations.

Benzodiazepines / Z-drugsSEVERE

Additive CNS depression and respiratory risk. Benzodiazepines are sometimes used to manage a difficult ketamine experience — this is a clinical intervention, not a recreational safety measure. Respiratory monitoring required if combined.

OpioidsSEVERE

Additive respiratory depression. Ketamine is used clinically as an opioid-sparing analgesic precisely because it works differently — recreational combination loses this separation and stacks respiratory risk.

MDMA / stimulantsMODERATE

Cardiovascular strain — stimulant-driven tachycardia combined with ketamine. Psychological effects may be unpredictably intensified. Hyperthermia risk. Increased disorientation and loss of situational awareness.

CannabisMODERATE

Cannabis can intensify dissociation unpredictably and dramatically. Many people who have difficult ketamine experiences report cannabis involvement. Individual variation is very large.

TramadolMODERATE

Both have serotonergic activity. Combined serotonin syndrome risk. Tramadol also lowers seizure threshold — ketamine has proconvulsant properties at high doses, making the combination unpredictable.

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