Welcome to JustAnswer! I am a licensed veterinarian and specialist and will do my best to assist you today!
I am sorry to hear about this concern.
1) Regarding the fleas - we typically consider using monthly preventatives for Flea issue, topicals such as Frontline or Advantage or oral such as Comfortis. These are the best, XXXXX XXXXX
2) Regarding the Iverheart - we typically do not re-dose this medication in situations such as this. We would give the next dose, as planned, the following month. If the pill remained in the stomach for 4 hours, much was likely absorbed - and re-dosing would not be performed. We do not want an accidental double dose and since we know that heartworms will not be a concern when they are on a monthly schedule but miss one or 2 doses (likely 3 doses) anyway.3) If you accidentally step on the pill - this is not a toxic chemical to people (as compared to other medications such as chloramphenicol for example)
That is an antibiotic - was just used as an example of a medication which we would worry about with people (not in your case)
For heartworm treatment.
Is it normal - no.
But remember, some people only treat for 6-8 months out of the year, and do not use the winter months.
But it is not going to hurt them.
I understand - the good news is that it is hard to "overdose" a dog on this as a prevention such as this has a lower concentration than if you were treating other diseases.
Heartworm is not common - the way to know is a blood test. This is not something you can see or feel on an examination.
Yes - there are some dogs that vomit on certain preventions - and if they do, we try to switch the medication to see if that helps.
If your dog does have a chronic history of intermittent vomiting, one dose is not enough to tell.
If several months go back and each month with administration your dog vomits, then yes, that would be a concern.
Same the next month - but if a pattern develops, then switch.
No - as listed above - we typically do not re-dose this, rather continue next month as planned.
If there are more than 3 months missed, yes.
Bathing can help remove them, but if you want PREVENTION, the options above are the most common.
It is a prevention.
We do not use this to kill.