Final answer:
Selective drug toxicity towards pathogens is more difficult to achieve in human cells than in prokaryotic cells due to structural similarities in eukaryotic pathogens and human cells.
Step-by-step explanation:
The question you've asked pertains to the difficulty of achieving selective drug toxicity in human cells compared to bacterial cells. This is indeed a challenging aspect of drug development, particularly when targeting eukaryotic pathogens such as fungi and protozoans that share more similarities with human cells. The similarity in vital structures such as ribosomes, cytoskeletons, and cell membranes between these eukaryotic cells and human cells makes it difficult to find therapeutic agents that are selectively toxic to the pathogens but not damaging to human cells. On the other hand, because bacteria are prokaryotic cells with significant differences from human cells, it is generally easier to target them without harming human cells, which is why we have a variety of effective antibiotics.