How much black widow venom would kill you instantly?
October 29, 2015 10:32 PM   Subscribe

My friends and I are having a disagreement. One friend says that if he hypothetically accumulated a "vial" full of black widow venom and injected it into himself that he would die instantly. I think that it would be horribly painful and not instant. Can anyone science me a real answer? No people or spiders will be harmed by this question.
posted by Marinara to Grab Bag (14 answers total) 1 user marked this as a favorite
Well, at the very least, we can try to estimate if a vial is even a lethal dose.

According to this study, the LD50 of American black widow (Latrodectus mactans) venom is 0.26 mg/kg. According to Wikipedia the average weight in N. America is 80.9 kg (you'll have your friend's actual weight, so adjust as necessary). Assuming the mouse study scales up to humans, that means you'd need around 21 mg of venom to have a 50/50 chance of killing someone. If we assume that spider venom has roughly the same density as water, then that would be 21 ml of venom.

Vials come in a variety of sizes, as small as 2 ml and as large as 40 ml (and probably even bigger). At the smaller end, I'm guessing it might not even be fatal.
posted by mhum at 10:53 PM on October 29, 2015 [2 favorites]

mhum: 1 milligram of water is 1μl, not 1ml.
posted by teraflop at 10:58 PM on October 29, 2015 [9 favorites]

teraflop: "mhum: 1 milligram of water is 1μl, not 1ml."

Oh snap. You're absolutely right. It's 1 g/ml, not 1 mg/ml. I knew something felt fishy.

In that case, even a 2 ml vial would contain around 1000 times the (presumed) LD50 of venom, so almost certainly enough to kill you. As for the exact nature of the death -- instant or drawn out -- I'm not sure I can say.
posted by mhum at 11:07 PM on October 29, 2015 [10 favorites]

Eh, I think you'd die from shock before your organs failed from the venom's extended neurologic effects, but that's just speculation. It'd suck damn hard either way, though.
posted by mosk at 11:12 PM on October 29, 2015

The mice in the study linked by mhum took at least 30 minutes to die.

Oh, I think I see how the analysis works. Figure 1 of the study is a plot of dose (units: mg/kg) vs. dose per survival time (units: mg/kg/minute), fit to a straight line with equation
dose = 33.9 minutes * (dose / survival time) + 0.26 mg/kg
The y-intercept is the LD50, since that's the dose for which the survival time becomes very long. The slope is how long it takes for you to die from an extremely large dose: in the limit where the LD50 is much smaller than the actual dose, the equation simplifies to
1 ≈ 33.9 minutes / survival time
So the linear model used to measure lethality suggests you take a finite time to die no matter how much toxin you're exposed to. I assume that for extremely large toxin exposures other mechanisms kick in which would kill you faster, but the linear model in the paper is good up to 15xLD50 ≈ 4 mg/kg.

So if you took 300 mg = 0.3 mL of black widow venom (intravenously) and responded like a mouse, you'd last about half an hour.

I still think it's be quicker to get enough venom to drown yourself.
posted by fantabulous timewaster at 11:48 PM on October 29, 2015

How fast is "instantly"? If you mean "No delay at all" I'm not aware of any poison that will do that. Not even nerve gas is that fast; a person has several seconds and if properly equipped can dose themself with an atropine injector and survive it.
posted by Chocolate Pickle at 12:57 AM on October 30, 2015 [4 favorites]

Assuming the mouse study scales up to humans,

You can't go straight from one to the other, you have to include a conversion factor. This is to take into account differences in metabolism and surface area of the different species.

It's been a few years since I did this but back then we used a Human Equivalent Dose conversion factor from Freireich, et al, 1966. Which apparently is not available online just to be annoying (we had beaten up photocopies that got passed between research groups). But anyway, in short you multiply the mouse dose by 0.08 to get the human dose using this method. So your 0.26 mg/kg becomes 0.0208 mg/kg

Now I think people tend to use a Body Surface Area Normalisation factor, eg Reagan-Shaw et al 2007. There you times by the mouse Km (3) and divide by the human one (37), so your dose of 0.26 mg/kg becomes 0.0210, so basically the same thing as with the HED.

So pick one then apply it to whatever mouse dose you decide is relevant.
posted by shelleycat at 1:16 AM on October 30, 2015 [5 favorites]

(Oh, my experience is with therapeutic drugs so looking for safe doses to use in clinical trials, it may be that venom/acute toxicity studies use some different type of species conversion that I've never heard of. But, in principle, the conversion factor idea should be sound.)
posted by shelleycat at 1:19 AM on October 30, 2015

The female of the species is more deadly than the male.

I assume we're talking about the female. I believe the main symptoms are muscle pain and cramps, and they take from fifteen minutes to an hour to spread from the bite over the whole body. Of course that's with a normal bite, which only involves tiny quantities and is rarely fatal, though it would certainly put a bit of a crimp in your week.
posted by Segundus at 2:48 AM on October 30, 2015 [1 favorite]

I think another factor is going to be where you inject it. Apparently black widow venom acts mostly on nerves, so the venom would have to get to an important nerve that could kill you and not just hurt and give you cramps. I'm guessing (not a doctor, not a toxicologist) that that the actual immediate thing that would kill you would be suffocation because of paralysis of your diaphragm/disruption of your breathing. Not instant.
posted by mskyle at 4:49 AM on October 30, 2015 [1 favorite]

Wikipedia says the toxins have a lag-period of 1 to 10 minutes.
posted by exogenous at 7:40 AM on October 30, 2015

you take a finite time to die no matter how much toxin you're exposed to

Well, the question surely can't be how much venom it would take for death to be literally instantaneous, can it? Like, it will always take some nonzero amount of time. It has to interact with the body. Though I suppose site of entry would make a big difference.
posted by kenko at 9:50 AM on October 30, 2015

shelleycat: "You can't go straight from one to the other, you have to include a conversion factor. This is to take into account differences in metabolism and surface area of the different species. [...] so your dose of 0.26 mg/kg becomes 0.0210, so basically the same thing as with the HED"

Dang. So a 2 ml vial would hold something like 10,000 times an LD50 dose, give or take.

So, I guess it'll come down to exactly how this venom can kill you. As several other people have pointed out, unlike some other spider venoms which are necrotoxic, black widow venom is neurotoxic. As near as I can tell, when black widow venom kills you, it's because it's messed up one of your autonomic systems that you need to live, probably either breathing or heart. So, then I would suspect that the actual time you have to live would depend on exactly where and how the venom was introduced into your body. If you got a shot direct to the heart, Pulp Fiction style, I'm going to guess it would mess you up right quick (although even in the case of a stopped heart, there is some delay before brain death, isn't there?). But what if you got a subcutaneous injection into, say, your foot? Or an intramuscular injection into the butt or deltoid? How long would it take for the venom to reach something that would kill you? I dunno.
posted by mhum at 10:09 AM on October 30, 2015

Toxicologist chiming in.

Nothing that acts by a toxic mechanism will kill a large organism--like a human--"instantly". There are very frankly too many nooks and crannies in us, and a lot of toxic substances have to more or less transport from A to B to C in the body to exert a truly lethal effect. That process takes time, even if it's not much time.

If you were a bacterium, something as simple as a detergent that disrupts your outer membrane would functionally kill you instantly by dispersing your contents into whatever medium you happen to be in. A human equivalent would be a very high force collision, but that's not a chemical insult like it can be at cellular scales.

If you were a mouse, or a hummingbird, substances that exert toxic effects by interrupting any part of the metabolic / cellular respiratory processes would bring you down quite quickly. Assuming a full block of something like electron transport or oxidative phoshorylation (an impossible goal, but you can get quite close to fully saturating those systems with a given toxin in a small volume/mass), the energy tap fueling most body processes grinds to a halt almost immediately and death can follow in moments.

But we're big things, with a lot of compartments, so our bodies need other, more targeted toxic substances in order to expire very quickly. Some of the known neurotixins fall into this category, like the paralytic shellfish poisons (PSPs). They fit, key-in-lock, to particular proteins that (more of then than not) are involved in the propagation of electrochemical signals throughout the nervous system and the systems it controls or influences. I worked on a project that was looking to find a non-animal assay to detect some of the PSPs. Assuming a large bolus dose of one of the PSPs could be administered directly into the central nervous system, or somehow perfused throughout the body very quickly, death would probably come in a few minutes. Same goes for cyanide formulations.

But no, no instantaneous toxic death for humans.
posted by late afternoon dreaming hotel at 10:13 AM on October 30, 2015 [18 favorites]

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