Can diarrhea and vomiting occur only after 3 days after the use of Pyrantelum?

If the reason was to take the drug, these symptoms would probably occur immediately, e.g. after a few to several hours, and not only after 3 days. Therefore, it is unlikely that these are side effects of Pyrantelum and that they will also appear after taking the next dose. These symptoms may be associated with a parasitic infection, so if they do not go away or worsen, you should consult a pediatrician. I attach links to helpful entries: https://www.gdziepolek.pl/kategorie/biegunka-i-wymioty-u-dziecka https://www.gdziepolek.pl/artykuly/czy-bac-sie-dzialan-niepozadanych-lekow