How do you administer the poison?
There are both steel and PVC pipes at the HomeCenter, so...
4"/100mm diameter PVC pipe, a funnel, and pour it up the dragons nose; if it's boiled cigarettes (nicotine) and fertilizer (Phosphorous, Sulphur), that dragon will be dead in short order!
That shit will fuck up any organic (carbon-based) life form!
I recommend PVC for the lack of weight, or even PEX piping; steel isnt bad, as it can withstand proximity to both poisons and dragons, but it may be rather heavy; even ¾"(2mm) thin-wall galvanized steel has some decent weight to it!
So, yeah; yard some 3½-4" PVC piping up the stairs with a coupla gallons of poison, and Bob's your uncle.
(I ain't figuring out all the metric equivalent to Freedom Units, rn)