Benzethonium increases the cytotoxicity of S(+)-ketamine in lymphoma, neuronal, and glial cells.
BACKGROUND
Ketamine has been demonstrated to be neurotoxic in animals as well as in patients. Preservatives added to ketamine have been accused to induce this neurotoxicity. Therefore, we investigated whether the most widely used preservative of ketamine-benzethonium chloride-enhances the toxicity of S(+)-ketamine in vitro in lymphoma, neuroblastoma cells and primary astrocytes.


METHODS
Human Jurkat T-lymphoma- and neuroblastoma cells (SHEP) were incubated for 24 hours with commercially available S-ketamine containing benzethonium, pure S-ketamine and pure benzethonium chloride. The rate of early- and late-apoptotic cells was evaluated by flowcytometry. In a second step the combined toxicity of benzethonium and ketamine was investigated in neuroblastoma cells and primary rat astrocytes in a mitochondrial activity assay (XTT). The additivity of the toxicities was evaluated by employing isobolographic analysis.


RESULTS
In Jurkat T-lymphoma and neuroblastoma cells benzethonium increased the toxicity of ketamine from 32% to 80% and from 64% to 84% cell deaths, respectively. In neuroblastoma cells as well as in primary rat astrocytes the measured combined toxicity was within the confidence interval of the calculated pure additive toxicity as seen in the isobolograms.


CONCLUSIONS
We conclude that benzethonium increases the local toxicity of ketamine in cells of hematopoietic, neuronal and glial origin in an additive manner. Therefore, caution is recommended especially when using preservative containing S-ketamine as an additive for long-term neuraxial analgesia.
Braun
Sebastian
S
Department of Anesthesiology, University of Düsseldorf, Düsseldorf, Germany.
Werdehausen
Robert
R
Gaza
Nina
N
Hermanns
Henning
H
Kremer
David
D
Küry
Patrick
P
Hollmann
Markus W
MW
Stevens
Markus F
MF
D000700:Analgesics / Q000633:toxicity*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001253:Astrocytes / Q000187:drug effects / Q000473:pathology; D001558:Benzethonium / Q000633:toxicity*; D002626:Chemistry, Pharmaceutical; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D006801:Humans; D020128:Inhibitory Concentration 50; D019169:Jurkat Cells; D007649:Ketamine / Q000633:toxicity*; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009336:Necrosis; D009457:Neuroglia / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D011310:Preservatives, Pharmaceutical / Q000633:toxicity*; D051381:Rats; D013997:Time Factors
D000700:Analgesics; D011310:Preservatives, Pharmaceutical; D001558:Benzethonium; D007649:Ketamine