NexGard for humans

August 20, 2020 10:12 PM

My pup takes NexGard once a month to control fleas, and it seems to work. It doesn't prevent bites, but (if the advertising is correct) once a bug bites him, the hoppers die within a short period of time, before they can lay eggs. Would a drug like this, approved for humans, potentially control bedbugs for those infested with them?

(Note, this is a curiosity-sating question, not actually advising people taking NexGard. I also don't have bedbugs.)

Could a medication like this potentially be a way of controlling other blood-feeding pests, like mosquitoes?

I'm mostly curious about bedbugs, which are notoriously difficult to eradicate once you have them. I guess the downside is you still have to be bitten, and you need to take it until all of the eggs have hatched and those new bugs have bitten you, too...which I suppose could take years if the eggs are environmentally durable.

posted by maxwelton to Health & Fitness (3 answers total)

Best answer: I was curious so I did a bit of searching and wasn't able to find any information suggesting that NexGard, or any of the class of parasitacide drugs (isoxazolines) that it belongs to, have ever been tested for use in humans. There was a paper a couple years back suggesting the use of these drugs for the control of malaria and other mosquito-borne diseases in places where they are endemic. As I understand it the idea in this case is not that the drug would prevent you from getting bitten, as the mosquito would already have bitten you and taken a blood meal by the time the drug acted on it; rather, that by supplying the drug to a large enough fraction of the population, mosquitoes would be unable to effectively spread malaria from infected people to uninfected ones, thus hopefully bringing the disease under control or even locally eradicating it. However as far as I can tell this has not (yet) led to clinical trials or anything exploring their use in humans.

There are also reports of relatively elevated rates of adverse neurological events from NexGard and similar drugs, which may explain why the companies owning their patents may not be pursuing developing them for use in humans. NexGard works by blocking inhibitory neurotransmission, and is selective for a version of the inhibitory receptor found in arthropods, which is why it's safe for dogs and cats to take. However it seems that there's been some suggestion that its selectivity isn't perfect, and that it may have some weak affinity for the inhibitory receptor in mammals too, leading to seizures and other problems in some animals. So although it's been FDA approved for veterinary use, the barrier for human approval is much higher, as are the potential legal costs to the pharmaceutical company if it turns out that there really is an increased risk of neurological side effects that goes undetected during clinical trials.

So although this is pure speculation, I would guess that the pharmaceutical companies making these drugs have done some internal risk-benefit calculus and decided that it's not worth sinking resources into trying to get the drugs approved for human use, since the market for dealing with bedbugs is probably not that large (yet, anyway), the market for mosquito-borne diseases is probably not that profitable, and the potential legal costs with a drug for which they already have at least some evidence for serious side effects are just too high.
posted by biogeo at 11:09 PM on August 20, 2020 [8 favorites]

Aside from the above excellent comment - I’ve had bedbugs before, and once I realized I had them, I would not have chosen a solution that involved letting them continue to bite me for a few weeks. And even if that had been ok with me, it wouldn’t have been ok with my employer, or anyone I rode the subway with...

Mosquitos would be a different story of course.
posted by showbiz_liz at 7:22 AM on August 21, 2020 [1 favorite]

Best answer: There has actually been research on the use of ivermectin which is approved for human use and very safe for this very purpose.

This later paper and this one by the same group go into more detail.

You can see from the final paper that it worked quite well. The blood sample taken 4 hours after taking ivermectin led to an 11-fold decrease in bed bug population, all blood samples taken within 60 hours led to a decrease. There was also substantial incapacitation and reduction in egg laying.

For most indications, ivermectin is dosed 1x. It's not clear whether a single dose would be enough. I kind of doubt it since bed bugs can go a few days between feedings. For some indications, it is given multiple times and its known to be pretty well tolerated at 10x higher doses than standard (but that's not been tested that much since it works really well at the standard dose).

I'm sure this has not been developed because even if it worked in practice, it's kind of a tough sell, a substantial part of the target market doesn't have much money, and domestic pest control is not covered by medical insurance so you'd have to be price competitive with pest management companies.

Full disclosure: If I had bedbugs, I would try it in addition to getting pest controllers in but I am a bit unusual.
posted by atrazine at 9:18 AM on August 21, 2020 [8 favorites]