Poisons, toxins and dosage

[vicky_molokh]

Greetings, all!

First, obligatory disclaimer: I know that the rules are simplified for playability, but OTOH we all know that SJG/GURPS tries to seriously research subjects before publishing, and stay pretty close to real life as far as roleplaying games go (but of course nobody's perfect).

That being said, I'm trying to figure some specifics behind poinsons, toxins and other chemicals that have effects on characters. I know that 'a dose' is a fuzzy amount of a chemical that produces the listed amount of Bad Stuff (e.g. 4d for Cyanide), can be used to envenom a piercing or impaling weapon (e.g. arrow tip with frog poison) once (B439), or about 1/3 of an edged weapon, or fits into a typical hollow bullet of Civil War era onwards (HT167). And retaining this relationship is important for keeping the game playable.

But then there's the Dan-Inject dart rifle, which can deliver up to 6 doses per dart. Said darts are somewhere between 2 and 10ml depending on model.

Now, here's what I've been examining:
LD50 for an irresistible poison (such as Cyanide) is roughly equivalent to 6d of damage. I.e. about 1½ 'GURPS doses'. The calculation is somewhat harder for poisons with resistance rolls, and even harder for poisons with resistance rolls and cycles.

Thing is, real-life LD50 of Cyanide for Blood Agents is something like 1-3mg per kg of body mass, or about 0.1-0.3g per adventurer (assuming HT10 and up to 200lbs mass). It is 0.7g/ml. So at about 2-7 times LD50 per ml. Given all the possible troubles of delivery, let's count that as 2 LD50s (i.e. count the 0.3g = LD50 benchmark). That's roughly equivalent to 3 'GURPS doses' (2×6d = 3×4d).

That seems to indicate the default assumption is that Dan-Inject Standard will use 2ml darts. Which deliver up to 6 doses of a chemical. But what happens in case of 10ml darts (which do exist)? Delivery of up to 30 doses. Nasty.

Comments? Corrections?

Thanks in advance!

[Bruno]

(The following is a little stream of consciousness, skip down closer to the end if you just want my conclusion)

Well, the first obvious comment is "yup, nasty".

The second one is that there's habitually a problem with hypodermic dart guns delivering a partial dose - the large game dart may have 30 doses of Cyanide in it, but may deploy anywhere between 1d6 doses to the full load. I'm not sure if there's rule for that particular problem yet.

There's a difference between having to buy 30 doses and only getting 6 delivered, and only having to buy 6 doses, so I wouldn't handwave that as the rule.

Not that this makes me feel any safer about being hit with it.

The third comment is that Cyanide may not have been a good "model toxin", even though it's mechanically convenient - does this indicate the Dan-Inject needs tweaking, or Cyanide needs tweaking? We can't tell, because its one data point.

Comment on the comment: The Dan-Inject is meant to deliver a non-lethal dose of a sedative - which I suspect is a much higher volume.

As a random aside: envenoming a blade (fairly cinematic) or an arrow/dart (not cinematic) requires quite a different preparation of the toxin than the way you'd prepare it for hypodermic injection - you need it to be viscous/hardened on the blade or it's just going to drip off, which means there's probably a significant weight of binder and carrier agent included, and the "envenoming" form is going to therefore take up more volume and weight per dose. Not that going from 1 mL to 10 mL matters much in the grand scheme of gaming, but PCs shouldn't be casually using a preparation for one use in another situation.

Actually, that's probably a good point here: you can't inject basic cyanide. 0.3g of solid at room temperature sodum-cyanide is just going to sit in the dart doing nothing useful. You can put it in someone's food like that, and most food is wet enough to dissolve it. However, to inject it, you'll need to dissolve it in water - which is going to pretty significantly increase the volume and weight per dose.

[Anthony]

The cyanide LD50 you seem to have found is for hydrogen cyanide, which is a gas and therefore not directly suitable for injection. I'm not sure exactly how much other stuff you'd need to mix it with to have a suitable injectable liquid. Sodium cyanide crystals would at least double the dose requirements.

[Flyndaran]

Some millipedes produce hydrogen cyanide. Just an interesting fact I discovered. Nowhere near enough to harm a human.
But in story, toxins are always fully effective rather than the long sickness and eventual total/partial recovery of many real world environmental/intentional poisonings.