Smell vs kill?

Cecil's Columns/Staff Reports
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http://www.straightdope.com/columns/read/1240/how-do-they-know-what-lethal-gases-smell-like

On a similar vein. As I am a sufferer of gout I morbidly looked up the lethal dose of Colchicine vs therapeutic dose.

The gap is amazingly small! Documented lethal doses are well lower than 10x therapeutic dose depending on body-mass and prescribing practices. Is this a new low? Or are there other popular drugs that are even more touchy?

FYI the new prescribed dose here for Colchicine is 1500 micrograms total in one hour - then none - unlike the previous dosing which was to keep taking 500 micrograms every three hours till you start vomiting and refuse any more (the doctors describe it as ‘self limiting’)

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A brief bit of research puts some dosing schemes at 600 micrograms per hour till ‘self limiting’ i.e. the puking and shitting makes you refuse any more. Other research shows 8000 micrograms total dose has been fatal. Compare that to the standard dose of 500 or 600 micrograms per tablet.