Introduction

An antimicrobial drug is a chemical substance that destroys pathogenic microorganisms with minimal damage to host tissue.

Antimicrobial drugs should:

1. Have selective toxicity – that is, should be toxic to the microbe not the host

2. Not provoke hypersensitivity

3. Be soluble in body fluids so that they can get into the areas where the infection exists

4. Should be cleared from the blood fast enough that toxic situations do not occur, but not so fast that therapeutic doses cannot be reached.

5. Have a long shelf life – this makes them less expensive, more readily available and available for use in rural areas.

6. Not provoke resistance

Chemotherapeutic agents include chemicals that combat disease in the body.

The History Of Chemotherapy

Paul Ehrlich developed the concept of chemotherapy to treat microbial diseases: he predicted the development of chemotherapeutic agents, which would kill pathogens without harming host.

Sulfa drugs came into prominence in the late 1930s.

Alexander Fleming discovered the first antibiotic, penicillin, in 1929; its first clinical trials were done in 1940.

The Spectrum Of Antimicrobial Activity

Antibacterial drugs affect many targets in a prokaryotic cell.

Fungal, protozoan, and helminthic infections are more difficult to treat because these organisms have eukaryotic cells.

Narrow –spectrum drugs affect only a select group of microbes—gram positive cells for example; broad-spectrum drugs affect gram-negative cells.

Small, hydrophilic drugs can affect gram-negative cells.

Antimicrobial agents should not cause excessive harm to normal microbiota.

Superinfections occur when a pathogen develops resistance to the drug being used or when normally resistant microbiota multiply excessively.