What did Ehrlich propose regarding the ideal drug, or magic bullet?

Ehrlich’s proposal about the ideal drug, often referred to as the "magic bullet," emphasizes that such a drug should precisely target the disease-causing agents while leaving healthy tissues unharmed. This concept was groundbreaking in the field of medicine, as it laid the foundation for the development of targeted therapies that selectively target pathogens or cancer cells, minimizing collateral damage to normal cells.

The essence of his theory is that an ideal treatment would not just be effective in treating an illness but would specifically interact with the disease-causing entity, thus reducing side effects and enhancing patient safety. This notion has become increasingly relevant in modern pharmacology and therapeutic development, with advances in biotechnology leading to drugs that can specifically target molecular markers associated with diseases.

In contrast, the options that suggest the existence of such a drug being widely used or purely theoretical do not align with Ehrlich's views. While progress has been made in creating drugs that meet some criteria of a magic bullet, a perfectly ideal drug that entirely spares healthy tissues while being completely effective still remains a goal rather than reality. Additionally, the suggestion that a drug can harm healthy tissues while being effective introduces a trade-off that contradicts the very premise of Ehrlich's concept of an ideal treatment.