Why is it challenging to obtain selectively toxic drugs against fungi, protozoans, and viruses?

Verified step by step guidance

1. Understand the concept of selective toxicity, which refers to the ability of a drug to target and kill or inhibit a pathogen without harming the host's cells.
2. Recognize that fungi and protozoans are eukaryotic organisms, like human cells, meaning they share many similar cellular structures and metabolic pathways, making it difficult to find drug targets unique to the pathogen.
3. Note that viruses are obligate intracellular parasites that use the host's cellular machinery to replicate, so targeting the virus without damaging host cells is inherently challenging.
4. Identify that the similarity between host and pathogen in fungi and protozoans reduces the number of unique biochemical pathways or structures that drugs can selectively target, increasing the risk of toxicity to the host.
5. Conclude that the challenge in developing selectively toxic drugs against these organisms lies in finding molecular differences significant enough to exploit without causing harm to the host.

Key Concepts

Selective Toxicity

Selective toxicity refers to a drug's ability to target and kill pathogens without harming the host's cells. Achieving this requires exploiting differences between the pathogen and host, such as unique metabolic pathways or structural components.

Similarity Between Pathogens and Host Cells

Fungi, protozoans, and viruses often share many cellular features or rely on host machinery, making it difficult to target them without damaging host cells. For example, fungi are eukaryotic like humans, and viruses use host cell processes to replicate.

Challenges in Targeting Viruses

Viruses lack their own metabolism and depend entirely on host cells for replication, limiting drug targets. Antiviral drugs must interfere with viral-specific proteins or replication steps without disrupting host functions, complicating selective toxicity.