Ricin Toxin

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`Ricin Toxin’ brings together a collection of in depth and cutting edge reviews that focus on the current understanding of ricin toxins. This e-book provides a historical background, innovations in ...
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Discovery of an Effective Ricin Antidote: An Old Drug for a New Use

Pp. 182-196 (15)

Junfei Yin, Michael Fung and John W. Cherwonogrodzky


A cell-based high throughput screening assay (HTS) was established to screen the Prestwick Chemical Library for candidates that acted against ricin. Of 1120 compounds screened, only 7 were identified as ricin inhibitors. Secondary screening with cell cultures identified only ethotoin as a dose-dependent inhibitor against ricin induced toxicity. Ethotoin was further evaluated in two in vivo studies. Study 1: When mice were given intra-peritoneal injections of 5×LD50 ricin (1 μg) pre-incubated with ethotoin (1 mg), all mice survived (monitored for 14 days). In contrast, control mice without ethotoin died within 2 days. Study 2: When mice were given 2×LD50 ricin (0.2 μg) by the intranasal route and then given ethotoin by multiple oral/gavage deliveries (at 1, 2, 4, 6, 8 and 10 hr after intoxication) 40% of the mice were alive at day 14. In contrast, all control mice (those that received sterile saline instead) died between days 3-9. Hence ethotoin, given by one route (oral) could rescue some mice from ricin given by another route (intra-nasal). Our findings suggest that ethotoin, although now an abandoned anti-convulsant drug, deserves further investigation and development as a potential antidote against the ricin biothreat.


Ricin, antidote, repurposing, drug, ethotoin, anticonvulsant, rescue.


Defence Research and Development Canada (DRDC), Suffield Research Centre, P.O. Box 4000, Station Main, Medicine Hat, AB, T1A 8K6, Canada.