Ketamine: dosage

Nasal insufflation delivers 45 to 50% of the dose systemically, with peak blood levels at 15 to 20 minutes [1]. Oral ingestion results in less overall absorption [1], with absorption limited by extensive first-pass metabolism [2]; peak levels take 40 to 55 minutes to arrive [1].

A commonly reported recreational dose is around 100 mg [3], with subjective effects lasting roughly 30 to 60 minutes [3]. In medicine, sub-dissociative ("low-dose") ketamine is used for pain management, either alone or as an adjunct [4], and low-dose perioperative ketamine may reduce opioid consumption and chronic postsurgical pain after specific surgical procedures [2]. None of the sources here give a recreational dosing range, or a threshold separating a light dose from a heavy one — the clinical figures above are context, not a guide.

S-ketamine is roughly four times more potent as an anaesthetic and analgesic than R-ketamine, and about twice as potent as standard racemic ketamine [2]; esketamine also has approximately four times greater affinity for the NMDA-receptor binding site than arketamine, and increased analgesic potency compared with the racemic form [1].

Tolerance builds quickly with repeated use; sessions are better spaced at least four weeks apart to limit rapid tolerance and dependence [1]. Stopping after heavy, sustained use can produce withdrawal symptoms lasting several days [1].

References

1. Ketamine: an updated review of use and harms (accessible) — UK Government (Advisory Council on the Misuse of Drugs)
2. Ketamine: A Review of Clinical Pharmacokinetics and Pharmacodynamics in Anesthesia and Pain Therapy — Clinical Pharmacokinetics (Springer)
3. Ketamine (drug fact sheet) — DEA Diversion Control Division
4. Ketamine - StatPearls — NCBI Bookshelf (StatPearls)