Best fix for this mistake (flea prevention med on cats)?

In My Humble Opinion
1

I have three cats and I dose them regularly with the flea prevention stuff you apply to the backs of their necks (Flea 5X Plus for cats from Pet Meds, to be precise).

With three cats who aren’t always around at the same time, I have a system so that I don’t get confused as to who has been dosed and who still needs their squirt. The meds come in boxes of three doses, so I open a box, write the names of each cat on the box, and check off the names as I corner and dose each cat.

I thought that’s what I did a couple of days ago, and if you’d asked me I would have said “yup, got all three.” But just now, when I went to trash the box that the meds came in, only one cat’s name was checked and there was one dose left inside the box.

So I gather what happened is that I dosed one cat, checked him off, dosed a second cat…and the phone rang or something, completely distracting me.

So now I have three cats, one of which I know got dosed, and two others - one of which got their med and the other didn’t, only I don’t know which is which.

I’m trying to decide the best way to handle this. I don’t want to overdose by giving both cats the meds right away, in case it would be harmful to the overdosed cat, but I also don’t want to let the other cat go too long without prevention. (I had an issue with a flea infestation a few years ago and NEVER want to go through that again.)

Anyway, here’s my thought. A while ago I was talking to a guy who takes in strays and cares for about 25 cats on his farm. I remarked, “flea medicine for all those cats must cost a fortune!” and he said, “well, the vet told me that even though the medicine instructions say to administer the stuff once a month, you can get away with doing it once every 3 months, so that’s how often we do it and we’ve never had a problem.”

Based on that I keep to a five-week cycle rather than 4, but I’ve not been willing to risk three months. In this case, I’m tempted to dose all three cats after 4 weeks, which would mean the skipped cat had to go 9 weeks without a fresh dose. If it’s true that the medicine will actually prevent fleas for 12 weeks, then 9 weeks should be fine.

But I’m just making a wild guess based on hearsay. I have no idea if that vet knew what he was talking about.

Anybody know anything about the effectiveness/toxicity of the flea meds and have comments on what I should do?

2

That stuff contains fipronil which can be toxic but seems less of danger when applied externally. I’d check with a vet to be sure, you might need to wait before dosing them again. There are a number of ‘Pet poison control’ websites and phone numbers, I don’t know anything about them, but maybe start with the ASPCA animal poison control number - (888) 426-4435

3

The insecticide on the two cats will also protect cat #3 to a useful degree. I’d just wait.

4

I’d call your vet. and ask.

If for some reason you can’t do that, I’d wait.

5

There’s no harm in waiting, but neither are the cats going to be harmed by a shortened cycle. Flea 5X Plus just has a single “cat” dose designed for cats over 1.5 lbs. The toxicity calculation is going to assume a worst case where the cats ingest the full dose. Assuming your cats are >3 lbs, a doubled dose is doing to be within the normal safety limits. And they will be even farther away from the safety limits if they don’t in fact lick the dosed area.

There’s some toxicity info here:
https://apvma.gov.au/sites/default/files/publication/15191-fipronil-prf-vol2-animal-safety-literature_0.pdf

It’s a little hard to gather the full picture, but here’s one relevant quote:

However, ingestion of fipronil concentrate (packaged to dispense 13.4 mg/kg per tube) may
approach acute toxic doses (75 mg/kg in mice), particularly if the entire contents (3-6 tubes) of a
package are ingested (Mondot and Dange, 1995). This would not be considered normal use and
would fall under inadvertent toxicity. Some ingestion may also occur following licking and
grooming of the site of application, despite the relatively low accessibility of this site (normally the
back of the neck).

The cat version of Flea5X Plus has ~50 mg of fipronil. Even if the cat fully ingested two full doses, it would be well under the acute toxic threshold unless it was a tiny kitten.

6

One thing you can do is give the cats a flea pill this month. It won’t interfere with their drops.

7

I’d wait also. I once killed some kittens overdosing them on flea meds, so that influences my answer.

8

And I’ve seen kittens killed by severe flea infestation.

I use Advantix on our dogs, which I apply every 3 weeks most of the year, every six weeks during the winter.

9

But the OP’s cats aren’t going to develop that level of flea infestation suddenly overnight (if ever at all.) It would come on gradually, and the fleas would be obvious to a human paying attention to the cats well before they reached a dangerous level.

If you want to do a more careful check, get a flea comb, and run it over the cats every couple of days.

10

I’d forgotten about nitenpyram, the stuff that @needscoffee suggested - boy that stuff is GREAT. It was hugely helpful when my poor Zoey had fleas and I was still fighting the infestation in the house (I couldn’t fumigate because it was a tropical house with open slats that couldn’t be sealed up, so I had to clean all the rugs and upholstery religiously every day for weeks - it was NOT fun.) I hope I won’t need it but if I do I’m glad it’s available.

I’m going to call the vet today though I’m not convinced I’ll get an answer very quickly - they seem to be pretty overworked so I predict I’ll just have to leave a message and see if/when they respond.

I have a flea comb and, assuming I don’t end up dosing both cats, will use it frequently - thanks for the suggestion @thorny_locust .

11

I hope you hear from the vet. I don’t think you’re about to get a major flea infestation, two of them have had the medicine, and if they share laying around spaces the third one is likely to be protected. With no other info I’d wait for half the cycle to go through and dose them again. The previous dose may be effective for that long and the dosages must have been set to account for occasional more frequent use.