A comparison of the pharmacokinetics and NMDAR antagonism-associated neurotoxicity of ketamine, (2R,6R)-hydroxynorketamine and MK-801

• Published in: Neurotoxicology and teratology Vol. 87; p. 106993
• Main Authors: Morris, Patrick J., Burke, Richard D., Sharma, Alok K., Lynch, Daniel C., Lemke-Boutcher, Leslie E., Mathew, Shiny, Elayan, Ikram, Rao, Deepa B., Gould, Todd D., Zarate, Carlos A., Zanos, Panos, Moaddel, Ruin, Thomas, Craig J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2021
• Subjects: Animals; Antidepressive Agents - administration & dosage; Antidepressive Agents - pharmacology; Behavior, Animal - drug effects; Depression - drug therapy; Disease Models, Animal; Dizocilpine Maleate - pharmacology; Ketamine; Ketamine - analogs & derivatives; Ketamine - pharmacology; MK-801; Neuropathology; Neurotoxicology; NMDAR antagonists; Olney lesions; Pharmacokinetics; Rats; Rats, Wistar; MK-801; Ketamine; Neuropathology; Neurotoxicology; NMDAR antagonists; Olney lesions; Pharmacokinetics
• ISSN: 0892-0362; 1872-9738
• DOI: 10.1016/j.ntt.2021.106993

With the increasing use of ketamine as an off-label treatment for depression and the recent FDA approval of (S)-ketamine for treatment-resistant depression, there is an increased need to understand the long-term safety profile of chronic ketamine administration. Of particular concern is the neurotoxicity previously observed in rat models following acute exposure to high doses of ketamine, broadly referred to as ‘Olney's lesions’. This type of toxicity presents as abnormal neuronal cellular vacuolization, followed by neuronal death and has been associated with ketamine's inhibition of the N-methyl-d-aspartate receptor (NMDAR). In this study, a pharmacological and neuropathological analysis of ketamine, the potent NMDAR antagonist MK-801, and the ketamine metabolite (2R,6R)-hydroxynorketamine [(2R,6R)-HNK)] in rats is described following both single dose and repeat dose drug exposures. Ketamine dosing was studied up to 20 mg/kg intravenously for the single-dose neuropathology study and up to 60 mg/kg intraperitoneally for the multiple-dose neuropathology study. MK-801 dosing was studied up to 0.8 mg/kg subcutaneously for both the single and multiple-dose neuropathology studies, while (2R,6R)-HNK dosing was studied up to 160 mg/kg intravenously in both studies. These studies confirm dose-dependent induction of ‘Olney's lesions’ following both single dose and repeat dosing of MK-801. Ketamine exposure, while showing common behavioral effects, did not induce wide-spread Olney's lesions. Treatment with (2R,6R)-HNK did not produce behavioral effects, toxicity or any evidence of Olney's lesion formation. Based on these results, future NMDAR-antagonist neurotoxicity studies should strongly consider taking pharmacokinetics more thoroughly into account. •MK-801 demonstrates a pronounced sex-based disparity in pharmacokinetics in rats.•MK-801 induces dose-dependent Olney's lesion formation in Han Wistar rats.•Intravenous ketamine does not produce Olney's lesions in Wistar rats up to 20 mg/kg.•(2R,6R)-HNK does not demonstrate any neurotoxicology at doses up to 160 mg/kg.