My memory says certain Asian Species are a problem. It is not a case of making things worse, it is a case of the medication having very low cure rate, like 20%.
That is why cofactors, and comeds are used, to increase odds of having a formula work.

The flatworm formula I used had Praziquantel, Vitamin D, Calcium, and Albendazole. I had several species, and it took several times and formulas to cure all the species.

Studies say artemether or artesunate are comeds for schistosomiasis.

https://mdpi-res.com/d_attachment/molecules/molecules-19-15058/article_deploy/molecules-19-15058.pdf

There also may be old world medications that work on resistant species.

In an ideal world, DNA testing is preformed, and doctors know which meds have the best odds to cure an infection. This is only in the realm of research labs. parasite treatment has not developed to the exact Science level that bacterial treatments have. The best approach is to have an exact plan, dose routine, established before beginning. There also may be retreatment routines, say in 28 days, that have been developed or tested in studies.

Each species have a different life cycle, which defines any retreatment schedule.

I am not aware of any long term resistance issues. Only the aforementioned Species that may not respond to Praziquantel. This has to do with the species being resistant or have low cure rates. The word resistance is actually not being used properly here, it is just a low percentage of cure. There has been discussions of resistance with other meds and infections, but not with Praziquantel.

Ineffective treatment can be from coinfections, complications, or immune weakness like heavy metal toxins.
That is why a complete evaluation of "other" health issues should be made prior to any attempt.