PennEd
I have searched the scientific literature and;
1 there are very few clinical trials for fenbendazole in humans, most are last resort clinical cancer trials
2 I could not find no long term study for fenbendazole in humans
3 it has serious side effects in case of kidney and liver problems, it can be deadly if taken with acetaminophen ( tylenol )
4 Long term ( preventative measure ) taking this medication in animals is not good as it impacts the immune system so no way for long term use.
ref;
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9413524/
In brief, mebendazole or other similar medication prescribed for humans is the best choice, it was studied in humans and side effects are well known. An evaluation of the patient health is best before prescribing this medication. mebendazole can be used very sporadically in case of an infection but like most medication it should not be taken if there is no problem to start with.
The best course of action is to get tested once a year for parasite detection if there is an infection they will tret it using a treatment protocol that is best for the patient.
i hope it helps,
Peace.