Is Ketamine Neurotoxic?

Original Article ↗ Hacker News Discussion ↗

Dosage, Routes, and Article Accuracy

  • Multiple commenters attack the article’s dose comparison as wrong or misleading:
    • 0.5 mg/kg is a per-dose IV/IM amount (often given 1–2×/week for depression, more for anesthesia), not a daily oral/intranasal amount.
    • 0.5 mg/kg for a 70 kg person is ~35 mg IV; saying 500–1000 mg/day is “100–300×” this is mathematically off, and also ignores route-of-administration (ROA).
  • ROA matters: rough figures cited are ~100% bioavailability IV, ~80% IM, ~20% intranasal, so mg numbers are not directly comparable.
  • Several people say 1 g/day is an extreme but real dose among chronic abusers; others note typical recreational doses are in the 30–75 mg/snorted range.
  • There’s confusion over what “average user” means. Many argue the article is really describing heavy/chronic abusers, not typical experimenters or occasional users.
  • Commenters also note other basic pharmacology errors and uncited claims, leading some to dismiss the article as sloppy or conclusion-driven.

Neurotoxicity vs. Neuroplasticity

  • One side stresses: ketamine (an NMDA receptor antagonist) and other NMDA-modulating drugs have well-known neurotoxic potential, especially at high or prolonged doses (e.g., lesions in animal models).
  • The other side highlights evidence that single or limited therapeutic doses increase neuroplasticity (BDNF, mTOR, synaptogenesis) in depression-relevant brain regions.
  • A key reconciliation suggested: both can be true. The same mechanism can yield beneficial plasticity at carefully controlled doses and regimens, and harmful structural changes with heavy, chronic, or high-dose exposure.
  • Some mention dopaminergic effects and strong tolerance, including reports that heavy users need gram-level doses and that tolerance may reappear quickly after abstinence.

Recreational vs. Therapeutic Risk

  • Broad agreement that:
    • Physician-supervised ketamine (e.g., IV infusions or monitored intranasal/lozenges) can be very effective for treatment-resistant depression/PTSD.
    • Street ketamine poses additional risks (adulterants, uncontrolled dosing).
  • Debate on severity and prevalence of harm:
    • Some report seeing dramatic cognitive decline and psychosis in heavy users.
    • Others emphasize few deaths from ketamine alone relative to opioids, but still warn about cardiovascular strain and bladder damage with long-term high-dose use.
    • Occasional deep “K-hole” use is described anecdotally, but its long-term risk level is seen as unclear.

Tolerance, Other Psych Meds, and Trust in Doctors

  • Ketamine tolerance is described as unusually persistent compared to stimulants, where breaks can reset sensitivity.
  • A long subthread compares this to Adderall/methylphenidate:
    • Some advise trusting psychiatrists’ dosing recommendations.
    • Others stress patient self-education and advocacy, citing overprescribing, side-effects, and the opioid crisis as reasons for skepticism.

Extreme Outcomes and Other Interventions

  • A widely discussed suicide note from a researcher who used ketamine and underwent ECT prompts:
    • Strong emotional reactions and reflection on depression, ambition, and meaning.
    • Disagreement about ECT: some say it can be life-saving; others report severe memory loss and no benefit.
  • Several commenters close with a pragmatic stance: high-powered interventions (ketamine, ECT) can be worth trying in severe, suicidal depression, but should be approached cautiously, with awareness of uncertain long-term neurotoxicity at higher or chronic doses.