In vitro activity: Benzethonium chloride inhibits acetylcholine responses in the α7 nAChRs in a mixed competitive and non-competitive manner but there is no voltage- or use-dependence of the response in either subtype. Benzethonium chloride produces mixed-type inhibition of choline esterase and acetylcholine esterase-affecting both Fmax and Km, Choline esterase is about 10-fold more sensitive to benzethonium chloride than acetylcholine esterase. Benzethonium chloride inhibits ICl(Ca) in response to 0.1 μM acetyl-beta-methylcholine in oocytes expressing m1 muscarinic receptors with IC50 of 0.88 μM. Benzethonium chloride combined with racemic S(+)/R(-) ketamine inhibits muscarinic signaling with a calculated IC50 of 15 μM and a Hill coefficient of 0.6. Benzethonium (5 μM) significantly increases cytosolic Ca(2+)-concentration, decreases forward scatter and triggered annexin V-binding affecting some 30% of the erythrocytes. Benzethonium (5 μM) further significantly enhances the effect of glucose depletion on cytosolic Ca(2+)-concentration and annexin V-binding, but significantly blunts the effect of glucose depletion on forward scatter. Benzethonium (5 μM) significantly enhances lactic acid formation but not ceramide abundance. Benzethonium chloride reduces cell viability with IC50 of 3.8 μM in FaDu, 42.2 μM in NIH 3T3, 5.3 μM in C666-1, and 17.0 μM in GM05757. Benzethonium chloride (9 μM) induces apoptosis and activates caspases after 12 hours in FaDu cells.

Cell Assay: Cells (FaDu, C666-1, NIH 3T3 and GM05757 cell lines) are seeded in 96-well plates at 5,000 per well in 100 μL of growth medium and allowed to incubate for 24 hours. Benzethonium chloride is then added, as indicated, in a total volume of 5 μL. After 48 hours, MTS assay is done according to the specifications of the manufacturer, with DMSO (0.1%)–treated cells as negative control and cisplatin (166.6 μM)–treated cells as positive control.

Eur J Clin Chem Clin Biochem. 1997 Aug;35(8):603-7; Clin Cancer Res. 2006 Sep 15;12(18):5557-69.