Final answer:
True, anti-infective drugs selectively target foreign organisms in the host body with minimal harm to the host. Antifungal drugs face challenges due to similarities between human and fungi cells, while antiviral drugs must avoid damaging the host cells that viruses use to replicate.
Step-by-step explanation:
It is true that anti-infective drugs act selectively on foreign organisms that have infected the host body. An important characteristic of these medications is selective toxicity, which ensures that the drugs target the infecting microorganisms with as little harm as possible to human cells. However, creating such drugs is more straightforward for bacteria than for eukaryotic organisms like fungi, protozoa, and helminths, because human cells share more similarities with these eukaryotic cells, making selective toxicity challenging. Viruses present another layer of complexity for antiviral drugs, as they replicate within human cells, necessitating a delicate balance to harm the virus without damaging the host cells.
The targets for anti-fungal drugs are limited compared to antibacterial or antiviral medications primarily because human cells are much more similar to fungi cells than to bacteria or viruses. Antiprotozoal drugs vary greatly and need to be specifically effective against the target pathogen, such as the various strains of Plasmodium that cause malaria. For helminths, drugs are designed to kill adult worms, which are then expelled by the host's body.